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Astrobiology Adventures: Exploring Life Beyond Earth · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 0:00
  Jonti Horner: Hi there.
• 0:00
  Andrew Dunkley: Thanks for joining us again. This is Space
• 0:02
  Nuts, where we talk astronomy and space
• 0:06
  science. And my name is Andrew Dunkley, your
• 0:08
  host. Great to have your company. Now,
• 0:10
  normally I'd be joined by Professor
• 0:12
  Fred Watson Watson, but he is away, uh,
• 0:14
  visiting family at the moment. And because he
• 0:17
  was going to be away and then I'm going to be
• 0:19
  away and we tried to cram episodes in and,
• 0:21
  uh, we just couldn't do enough in the amount
• 0:24
  of time we had. Uh, we invited Professor
• 0:26
  Jonty Horner to join us and we're, uh, going
• 0:29
  to do some specials. You might have heard the
• 0:30
  last one, uh, which was very engaging
• 0:33
  and interesting and fascinating and long. Uh,
• 0:36
  this time we, we're going down a different
• 0:39
  road. We're going to focus the whole
• 0:40
  programme on
• 0:41
  astrobiology. Strap in.
• 0:44
  We'll do that right now. 15 seconds.
• 0:47
  Guidance is internal. 10,
• 0:50
  9. Ignition sequence.
• 0:52
  Jonti Horner: Star. Space nuts. 5, 4, 3, 2.
• 0:55
  Andrew Dunkley: 1. 2, 3, 4, 5, 5, 4, 3,
• 0:58
  2, 1.
• 0:58
  Jonti Horner: Space nuts.
• 1:00
  Andrew Dunkley: Astronauts report it feels good. And here he
• 1:02
  is again, professor of astrophysics at the
• 1:05
  University of Southern Queensland, Johnty
• 1:07
  Horner. G', day, Johnty G'.
• 1:09
  Jonti Horner: Day. How are you going?
• 1:09
  Andrew Dunkley: I'm well. Good to see you again.
• 1:12
  And, uh, we've got a lot to talk about, so I
• 1:14
  think we're going to just dive on in.
• 1:16
  Now, in preparation for this astrobiology
• 1:19
  chat, you sent me a paper that you wrote,
• 1:22
  uh, and published on the Arxiv website.
• 1:25
  Uh, it's, um, ancient.
• 1:28
  Yeah, it's, it's coming up on 16
• 1:31
  years since you wrote that. But one of the
• 1:33
  interesting parts was, um, look, it's
• 1:36
  been a couple of decades now that we've been
• 1:38
  finding exoplanets. And as technology
• 1:40
  improves, it's only a matter of time before
• 1:43
  we start finding Earth like planets. And
• 1:45
  that's really going to make the search for
• 1:48
  life beyond our solar system really,
• 1:51
  really interesting. So those 16 years have
• 1:54
  passed. Have we got the. Have we got the
• 1:55
  equipment yet? I suspect we have.
• 1:58
  Jonti Horner: It depends where you're looking, I think. I
• 2:00
  mean in terms of looking at the planet. Round
• 2:02
  of the stars. We can now learn a lot more
• 2:05
  about them than we could 16 years ago when I
• 2:07
  wrote the paper, that particular paper. But
• 2:10
  we're still not there yet. And it's a
• 2:12
  perpetual thing. No matter how hard you work,
• 2:15
  there's always more to do. The other thing
• 2:17
  that goes along with it, which I think is
• 2:19
  worth saying right up at the very start, is,
• 2:21
  uh, searching fly false worries going to be
• 2:24
  one of the hardest things we've ever done.
• 2:26
  And, um, absence of evidence is not
• 2:28
  necessarily evidence of absence.
• 2:31
  What I mean by that is we could, in a
• 2:34
  remarkable turn of events in the next few
• 2:36
  months, find life elsewhere. You know, that's
• 2:38
  kind of the ultimate extreme, soonest
• 2:40
  possible. Um, very unlikely to happen.
• 2:43
  Alternatively, we might still be looking in a
• 2:45
  century. If we're still looking in a century.
• 2:49
  That doesn't mean that there isn't any life
• 2:51
  out out there, but what it will suggest
• 2:53
  to us is that life is relatively scarce.
• 2:56
  So to me, the sooner we find life elsewhere,
• 3:00
  that 8 will be awesome. Because, hey, look,
• 3:02
  we found life elsewhere, and we've answered
• 3:03
  the ultimate question, are we alone? But the
• 3:06
  sooner we find life elsewhere, the other
• 3:07
  thing it's telling us is that life must be
• 3:09
  fairly common in the universe. The scarcer
• 3:11
  life is, the harder it will be to find, and
• 3:14
  therefore the longer it will take us to find.
• 3:16
  And now the ultimate extreme of that is that,
• 3:19
  uh, this is the only place that there is
• 3:20
  life. And it'll be very hard
• 3:23
  to conclude that even if we were talking
• 3:26
  through a time warp, in 10,000 years, when
• 3:28
  humanity is taking its fledgling steps into
• 3:30
  the galaxy or whatever, if we haven't found
• 3:33
  life by then, we'll be confident that life is
• 3:35
  very rare and very precious. That doesn't
• 3:38
  mean that there is not life somewhere else in
• 3:40
  the universe. And it's one of the challenges
• 3:42
  with this. I would like to think that we'll
• 3:44
  find the answer to that question in our
• 3:45
  lifetime. But the only way we'll get an
• 3:48
  answer to the question, are we alone, um,
• 3:50
  within our lifetime? As if the answer is no,
• 3:52
  if that answer is that there is life
• 3:54
  elsewhere. And this is one of the big,
• 3:57
  really, really big open questions for
• 3:59
  humanity, open questions for science. You
• 4:01
  know, when I was a kid, when you were a kid,
• 4:03
  one of the big questions was, is the solar
• 4:05
  system unique? Or are there planets around
• 4:07
  other stars? And we'll talk about that more
• 4:09
  in the next episode. But there is nobody
• 4:12
  under the age of 30, 31 alive on
• 4:15
  this planet that grew up in that shared
• 4:16
  universe with you and I. So that fundamental
• 4:18
  question got answered and answered in ab.
• 4:22
  And answering that question is the first real
• 4:24
  step to say, is there life elsewhere
• 4:26
  beyond the solar system? Because in order to
• 4:29
  find life beyond the solar system, we first
• 4:32
  need to know that there's somewhere that life
• 4:33
  could exist. The question of life in the
• 4:36
  solar system is a different one. And that's
• 4:37
  all part of astrobiology. So if you bundle
• 4:39
  all of this together, that question of how we
• 4:42
  alone, um, is there life elsewhere? Which
• 4:44
  brings with it Questions like, what is the
• 4:46
  origin of life, why are we here? How did life
• 4:48
  begin, how did it get established, what are
• 4:50
  the processes needed? Everything like that,
• 4:53
  yeah, is what gets bundled in, in
• 4:54
  astrobiology. And astrobiology is a very,
• 4:57
  very weird science. I know certainly early in
• 5:00
  my career, a lot of older scientists viewed
• 5:02
  astrobiology in a similar way to the way a
• 5:05
  lot of astronomers view astrology almost. You
• 5:07
  know, they viewed it as being speculation,
• 5:09
  fiction and hook, you know, total bogus waste
• 5:12
  of time stuff. But it really isn't.
• 5:16
  Yeah, but one of the real challenges is, uh,
• 5:18
  it's not a question that one single
• 5:20
  discipline on its own can answer. Right. It's
• 5:22
  not like in astronomy, you, you're studying
• 5:24
  how, so you talk to astronomers in
• 5:27
  astrobiology, if we're looking at everything
• 5:30
  to do with life, astronomers like myself
• 5:33
  can't do it on their own, biologists can't do
• 5:35
  it on their own. You need geophysicists, you
• 5:38
  need chemists, you need every area of human
• 5:41
  scientific endeavour to come together.
• 5:43
  Because as scientists, our knowledge is
• 5:45
  somewhat siloed. I think I've said in
• 5:47
  previous episodes, the further you go away
• 5:49
  from what your speciality is, the more out of
• 5:51
  debt and the more superficial your knowledge
• 5:53
  is. So I always view my knowledge as being
• 5:55
  almost like a Christmas tree shape. I've got
• 5:57
  a lot of knowledge about a very narrow area
• 5:59
  at the top. And the further you go from that
• 6:01
  area, the less knowledge I have, but the
• 6:03
  broader my knowledge base gets. And I think
• 6:05
  every human's like that. And um, you can
• 6:07
  almost imagine that if you're trying to
• 6:09
  answer the question of what you need for
• 6:11
  life, where we should look, which, what we'll
• 6:13
  talk about a lot today. You need a level
• 6:15
  that's above a certain point on that
• 6:17
  Christmas tree of knowledge to be able to
• 6:18
  contribute to that from a scientific
• 6:20
  advancement point of view. And the area
• 6:23
  that you can cover yourself is generally
• 6:25
  fairly small. There's a lot of knowledge that
• 6:26
  is needed that is outside your silo.
• 6:29
  And so that's where the interdisciplinary
• 6:31
  nature comes in. No one discipline can answer
• 6:34
  it their own. And that means astrobiology
• 6:36
  conferences tend to be mind bogglingly
• 6:39
  bonkers. And you get people from very
• 6:41
  different disciplines along
• 6:44
  and you learn a lot that updates your
• 6:46
  knowledge from when you went to high school.
• 6:48
  You also learn a lot that isn't about the
• 6:50
  science, but is about the scientists.
• 6:53
  And it's really interesting because we all
• 6:54
  think we're individuals. It's like that Monty
• 6:56
  Python thing, isn't it? We're all individuals
• 6:57
  and there's a Voice at the back that goes,
• 6:59
  I'm not, I'm not. Yeah, it's a bit like that.
• 7:01
  Uh, we all think, we're all individuals and
• 7:03
  we're very unique in the way we think and the
• 7:05
  way we present. But when you go to one of
• 7:07
  these conferences, that's so
• 7:08
  multidisciplinary. The different
• 7:10
  disciplines present in different ways to one
• 7:13
  another. But within the discipline there are
• 7:14
  similarities, you know. So if you see the
• 7:16
  talks I give, I have beautiful pictures and
• 7:19
  bright text, white or yellow on them, limited
• 7:21
  text, usually a dark background. And that's
• 7:23
  really common for astronomers. You go to a
• 7:26
  talk by a kind of plate tectonics person
• 7:29
  and suddenly you've got this mishmash of
• 7:31
  colours on a total different background where
• 7:34
  there's a bit more text. But the colour
• 7:36
  schemes are a bit, to me, kind of psychedelic
• 7:39
  and like something you'd see out of a 1970s
• 7:40
  cartoon, you know, because they're used to
• 7:43
  working with these geological maps that, uh,
• 7:45
  um, have a very different colour palette and
• 7:47
  sensibility, I think. And then you get talks
• 7:49
  from the biologists where they've got the
• 7:51
  name of one bacterium and it fills half of
• 7:53
  the page because it's such a lengthy
• 7:55
  scientific name. And they've got loads of
• 7:56
  texts. And so you learn a lot about how
• 8:00
  what you study at university and what
• 8:02
  discipline you go into trains you to
• 8:05
  think and transit to problem solve. Because
• 8:08
  it trains you in a lot of different ways,
• 8:10
  essentially, programmes, people. And, um, you
• 8:12
  know, I find that side of things really
• 8:14
  fascinating because it's a good way to learn
• 8:16
  to improve your communication skills. And you
• 8:18
  also pick up all this abundance of,
• 8:21
  wow, I never knew that, you know. And that's
• 8:23
  what we need if we are to answer questions
• 8:26
  like, how did life begin? Where did life come
• 8:28
  from? Are we alone? Um, yeah.
• 8:30
  Andrew Dunkley: And that's really an interesting question
• 8:32
  because, uh, it could be life
• 8:35
  not as we know it.
• 8:36
  Like we, you know, we're assuming carbon
• 8:38
  based life forms, but there could be life
• 8:41
  forms that have been created out of a
• 8:43
  completely different soup mix. Two, uh,
• 8:45
  things I want to get out of the way quickly.
• 8:47
  The Drake Equation, which was, uh, created
• 8:50
  to try and assess how much intelligent
• 8:53
  life that was able to communicate existed in
• 8:56
  the universe. And the answer is still one.
• 8:58
  And the Fermi paradox, which says, you know,
• 9:01
  um, that statistically there's a
• 9:04
  high probability of extraterrestrial life.
• 9:07
  So where is everybody? And
• 9:09
  that's what astrobiology is really, isn't it?
• 9:12
  Where is everybody? And. And will they be
• 9:15
  people or will they be microbes?
• 9:17
  And I suppose my first question to you
• 9:20
  is, uh, you're talking about finding life
• 9:23
  outside the solar system. Aren't we likely
• 9:25
  to find it first within the solar system?
• 9:29
  Jonti Horner: So that's a really good question. I was going
• 9:31
  to talk about that a bit as well, because I
• 9:32
  think there are two different places.
• 9:35
  In a broad sense, we're looking for life
• 9:37
  elsewhere. One is in the
• 9:40
  outer solar system or on Mars, you know, in
• 9:42
  our solar system, on one of the planets or,
• 9:44
  uh, on the icy objects. And the other is
• 9:46
  beyond the solar system. And those two
• 9:48
  things have very different
• 9:51
  characteristics. What I mean
• 9:54
  by that is that, uh, objects that are in our
• 9:56
  solar system are in our backyard. They're the
• 9:59
  only things in astronomy that we can get up
• 10:01
  close and personal with. So in the solar
• 10:03
  system, the search for life elsewhere is
• 10:06
  being driven by robotic exploration. In the
• 10:09
  Moon. Yes, there's a little bit of
• 10:11
  observation from Earth. We saw that with the
• 10:14
  phosphine storey on Venus that I ranted about
• 10:16
  a little bit last week. Um, and, um, the
• 10:18
  wonderful caution shown by scientists that
• 10:20
  was not necessarily reflected in the
• 10:21
  coverage. Um, but a lot of the research
• 10:25
  in the solar system is robotic in nature. We
• 10:28
  send spacecraft to places to study them up
• 10:30
  close and personal. And we can't do that
• 10:33
  around other stars. Around other stars. It's
• 10:35
  very much a remote sensing type deal. So
• 10:37
  there are different ways of doing it. Now, I
• 10:40
  think there is a realistic chance we'll find
• 10:41
  life elsewhere in the solar system. There's a
• 10:44
  lot of good reasons for that. Now, before I
• 10:46
  dive into that a little bit, I'll just take a
• 10:48
  step back and come back to that point you
• 10:50
  made about life like us and carbon based life
• 10:51
  versus other things. Because it's really
• 10:53
  important to make explicit what is normally
• 10:56
  an implicit bias when
• 10:58
  scientists are talking about astrobiology.
• 11:01
  It's really made clear when you think about
• 11:03
  NASA and Issa's efforts on the moon, where
• 11:06
  they have. On, um, Mars, sorry, where they
• 11:08
  have aggressively said the strategy to look
• 11:10
  for life is to follow the water.
• 11:13
  What they're doing there is making
• 11:16
  an implicit assumption. That is an assumption
• 11:18
  that is not always written out and is clear,
• 11:20
  but is at the back of it, that life
• 11:23
  that we look for will be life like us. And I
• 11:25
  mean life like Earth life. Now we can
• 11:28
  imagine. You see it on science fiction all
• 11:30
  the time. You know, life that is very other.
• 11:32
  It might be molten metal monsters on a magma
• 11:34
  planet, or it might be an intelligent
• 11:36
  hydrogen cloud that nevertheless wants to
• 11:37
  flirt with Captain Kirk. It's
• 11:40
  very different kinds of life, but
• 11:42
  Fundamentally we only know of one type of
• 11:45
  life that does exist, and that's life
• 11:47
  like Earth life. And so when we
• 11:50
  look for life elsewhere, at ah, least in
• 11:53
  what is the early stages still, it is really
• 11:56
  important to look for something that we know
• 11:58
  can exist and does exist, rather than
• 12:01
  looking for things that we could speculate
• 12:02
  might exist. If you've got to focus your
• 12:05
  efforts with limited resources, it
• 12:08
  makes sense to follow the kind of well
• 12:10
  trodden footsteps of what we know about life
• 12:12
  on Earth. And um, from an astronomer's point
• 12:14
  of view, life on Earth needs three things.
• 12:16
  You know, it needs liquid water, it needs a
• 12:19
  source of energy and a source of nutrients.
• 12:20
  And quite often those two are the same thing,
• 12:22
  but not always. And wherever we find those
• 12:25
  things on Earth, we find life in abundance.
• 12:27
  And once life gets there, it's really hard to
• 12:29
  get rid of. You know, anybody who's had ants
• 12:31
  getting into their kitchen or the mice plague
• 12:33
  that we talked about last week knows just how
• 12:37
  life, once it gets established, keeps going.
• 12:40
  And so it makes sense. And a lot of what I'll
• 12:43
  talk about for all the rest of the episode is
• 12:45
  kind of based on this assumption that we're
• 12:47
  looking, at least initially for life like
• 12:50
  us, has the same needs as us. Where the US is
• 12:52
  abroad, the entire panel play of life on
• 12:55
  Earth rather than us as in me and the having
• 12:58
  this chat back and forward. What
• 13:00
  that leads to though is a lot of studies that
• 13:02
  have been done for the solar system are very
• 13:04
  water driven. And if you go back decades, you
• 13:07
  could go back to the late 1800s when people
• 13:10
  were obsessed with this idea that there was
• 13:12
  an advanced technological civilization on
• 13:14
  Mars that was running out of time because the
• 13:16
  planet was desolate and barren. And this was
• 13:19
  all motivated by the observations of the
• 13:21
  canali, the channels on Mars that don't
• 13:23
  exist, which were mistranslated as canals and
• 13:26
  canals on Earth are a very clear sign of
• 13:28
  human activity. Yeah, People at
• 13:31
  that time were so certain that we'd already
• 13:33
  found life that when there was a prize
• 13:35
  awarded, um, a prize laid
• 13:38
  out, sorry, in announced, I think it was like
• 13:39
  in 1899 or something, for the search for
• 13:42
  life, for the first person to discover life
• 13:44
  elsewhere, to find evidence of life
• 13:46
  elsewhere. That prize explicitly
• 13:48
  excluded Mars because it was felt that life
• 13:51
  on Mars was so well established that that was
• 13:53
  a no brainer. You know, it was such a thing
• 13:55
  in popular culture that when the War of the
• 13:56
  Worlds broadcast happened in the 1930s,
• 13:59
  people thought it was live news coverage and
• 14:01
  panicked.
• 14:01
  Andrew Dunkley: Yes. You know, the night that panicked
• 14:04
  America.
• 14:04
  Jonti Horner: Yeah. And there's this whole heritage of
• 14:08
  our expectation of life being common
• 14:11
  and it being lifelike, us requiring water.
• 14:14
  When we went to Mars, like in the 1960s with
• 14:17
  spacecraft, Mars was shown to be the
• 14:19
  desolate, arid world we knew today. And that
• 14:21
  put to an end the thoughts of an advanced
• 14:23
  civilization there. And, um, from that time
• 14:26
  onwards there was a period where arguments in
• 14:28
  astrobiology fell very much out of favour,
• 14:30
  out of fashion. And it was kind of viewed
• 14:32
  much more likely that life was almost unique,
• 14:34
  we were alone, um, there was no way you could
• 14:36
  look.
• 14:36
  And there's this argument that I often hear
• 14:39
  espouse that water is scarce in the universe.
• 14:43
  And that makes my head hurt. I think this is
• 14:45
  one of those big myths that is a myth of
• 14:47
  miscommunication or a myth of
• 14:51
  language being a personal
• 14:54
  thing. What I mean by that is, and I'm
• 14:56
  always trying to be very aware of this when
• 14:58
  I'm, uh, as a communicator, the
• 15:01
  words have different meanings to different
• 15:03
  people. And so the same word that I
• 15:06
  say you'll hear and it doesn't always mean
• 15:08
  the same thing to you or me. And one of the
• 15:10
  best things, best examples of this is when
• 15:12
  you get people who are trying to argue
• 15:14
  against an area of science, maybe vaccines,
• 15:17
  maybe climate change, maybe something less
• 15:19
  controversial. You'll often hear people say
• 15:21
  that, well, climate change is just a theory,
• 15:23
  or, uh, vaccines are just a theory, or the
• 15:25
  Big Bang is just a theory. And to a lot of
• 15:28
  people a theory just means a loose
• 15:31
  idea. A lot of people will say,
• 15:34
  why isn't your car starting this morning?
• 15:36
  Well, I've got a theory. To a scientist, a
• 15:39
  theory is a very different beast and it's
• 15:41
  tied to the ability to make testable
• 15:43
  predictions and, um, repeated testing.
• 15:46
  There's a lot of philosophy of science. I did
• 15:48
  a philosophy of physics course at, uh,
• 15:50
  university when I was 18 and I wish I'd done
• 15:52
  it when I was at the end of my degree. Not
• 15:53
  the start, because I'd have got a lot more
• 15:54
  out of it. But there are people who've
• 15:56
  aggressively studied the philosophy of the
• 15:59
  scientific method and even that philosophy
• 16:02
  varies a little bit, discipline to
• 16:03
  discipline. A lot of other disciplines that
• 16:05
  are the experimental ones are a very much
• 16:07
  more hypothesis driven than astronomy,
• 16:10
  where we say, I'm interested in what this is,
• 16:12
  let's have a look. There's not really a
• 16:13
  hypothesis. I just want to look at it and
• 16:15
  find out. At least that's how I work. But you
• 16:17
  also have this thing where, at least from my
• 16:20
  philosophy, you can never prove a Theory, but
• 16:22
  you can disprove a theory. What I mean by
• 16:24
  that is if you test a theory a million times
• 16:28
  and each time it's backs it up, you haven't
• 16:30
  proven that theory. You've just shown that
• 16:32
  theory is a very good approximation to what's
• 16:34
  actually happening. So take the example of me
• 16:36
  flipping a coin, I can have a theory theory
• 16:39
  that says coins will always land heads or
• 16:41
  tails. Test that a million times and odds are
• 16:44
  a million times you'll land heads or tails.
• 16:46
  But you've not proven that theory. You've
• 16:48
  just said it's a very close approximation to
• 16:50
  the truth. You could toss them 10 million
• 16:52
  times and one time your coin lands on its
• 16:53
  edge and balances. Yeah, that one
• 16:55
  observation. So as long as it's well
• 16:57
  documented and is repeatable is enough to
• 16:58
  kill that theory. And then you need to
• 17:00
  develop something more complex. You know,
• 17:03
  that's where it goes from.
• 17:04
  Now, that's a very roundabout way of coming
• 17:07
  back at this water being scarce myth.
• 17:10
  I think where that comes from is when you
• 17:13
  talk to me about water, I am,
• 17:16
  um, just thinking about the molecule.
• 17:18
  I'm not thinking about the physical state. So
• 17:21
  to me, water can be water ice, it can be
• 17:23
  liquid water, it can be water vapour. But to
• 17:26
  most people, if you say water, they visualise
• 17:28
  liquid water. Yeah, if, if I say, would you
• 17:31
  like some water? You're not expecting me to
• 17:33
  immediately start steaming your face. You're
• 17:35
  expecting a glass of water. Right.
• 17:38
  What that means is that when people look out
• 17:40
  of the solar system and look everywhere else,
• 17:42
  we see this thing that Earth is the only
• 17:44
  place where we have abundant liquid water all
• 17:46
  the time on the surface. And so people
• 17:49
  have this idea that water is scarce, where
• 17:51
  what they're really thinking is liquid water
• 17:54
  on the surface of an object is scarce.
• 17:58
  But that drove a lot of this idea that life
• 18:00
  will be scarce because life needs liquid
• 18:02
  water. On Earth, the earthy and lipidates
• 18:04
  with liquid water, ergo, uh, life will be
• 18:07
  scarce. That's moved on though, in about the
• 18:09
  last three or four decades, partially with
• 18:11
  the exploration of Mars, where we're getting
• 18:14
  an overwhelmingly greater amount m of
• 18:16
  evidence that Mars in the past was warm and
• 18:18
  wet, that it had oceans and lakes. They may
• 18:20
  have been slushy or they may have been
• 18:21
  properly liquid, but it had oceans and lakes
• 18:24
  for a long time of liquid water. And we've
• 18:26
  even got evidence that there is permanent
• 18:27
  liquid water on Mars as we're talking now in
• 18:29
  the form of liquid water in the Martian Mars
• 18:31
  polar ice caps. And you get temporary liquid
• 18:33
  Water running on the surface. The other thing
• 18:36
  we found in the solar system is liquid water
• 18:38
  in astonishing abundance in the outer solar
• 18:41
  system, protected by shells of ice on the
• 18:44
  icy satellites of the giant planets. On the
• 18:47
  dwarf planet Pluto, or inside the dwarf
• 18:48
  planet Pluto, probably in the larger, uh,
• 18:51
  Edgeworth Kuiper Belt objects, Trans
• 18:53
  Neptunian objects, maybe in other places as
• 18:55
  well, even in places as small as Enceladus.
• 18:58
  So there's been this revolution from the
• 19:01
  point of view of the solar system through my
• 19:02
  lifetime that actually liquid water isn't
• 19:05
  scarce. Coupled to the fact that the Earth is
• 19:08
  actually remarkably dry as a planet, that
• 19:10
  suddenly opened up people's perspectives
• 19:11
  again that the solar system is a good place
• 19:13
  to look for life. And that's driving a lot of
• 19:16
  exploration, a lot of missions. All the Mars
• 19:17
  exploration past and, um, future focused
• 19:20
  around that idea. The fact that we've got two
• 19:22
  missions going to the Jovian IC satellites at
• 19:24
  the minute Juice and, um, the Jupiterizing
• 19:26
  Moons Explorer and the Europa Clipper, which
• 19:29
  are to characterise those moons better to
• 19:31
  prepare for potential future landings in the
• 19:33
  2000-40s or-50s to get through the ice and
• 19:35
  look at what's underneath. We've got the
• 19:37
  Dragonfly mission going out to Titan,
• 19:40
  launching in a couple of years time, probably
• 19:41
  next year, ah, hoping to get there 2034.
• 19:44
  That will land on the only other place that
• 19:46
  has liquid on its surface exposed to the
• 19:49
  atmosphere in the solar system, and that's
• 19:50
  Titan. With lakes of liquid methane and
• 19:52
  ethane. The water there is harder than
• 19:54
  granite and makes up the mountain. But
• 19:57
  there's this huge effort to explore our solar
• 19:58
  system and actually go there and look, which
• 20:00
  we can't do when we're looking at planets
• 20:02
  around other stars. And by going there and
• 20:05
  looking if there is anything there, past or
• 20:08
  present, eventually we'll find it. Now, that
• 20:11
  immediately then poses a really fascinating
• 20:13
  one. So if we find life on Mars or find life
• 20:16
  on Europa, if we can
• 20:19
  look at that life and figure out
• 20:22
  its heritage, figure out its DNA, and I'm not
• 20:25
  a biologist, so I'll be a little woolly on
• 20:27
  that. It will be very quick and very
• 20:29
  apparent whether that life has a shared
• 20:31
  origin to life on Earth or whether it has a
• 20:33
  separate origin to life on Earth. Now, the
• 20:35
  separate origin would mean that life got
• 20:37
  started simultaneously on two
• 20:40
  objects in the same planetary system in
• 20:43
  an icy backwater of a fairly unremarkable
• 20:46
  galaxy. If it got started two places side
• 20:48
  by side, surely that means life gets started
• 20:51
  more easily than we expect. Therefore, life
• 20:53
  should be common in the universe. That would
• 20:56
  be an obvious logical continuation. The other
• 20:59
  option is that we find life elsewhere in the
• 21:00
  solar system and it has a shared heritage to
• 21:02
  life on Earth. What that means is that, uh,
• 21:04
  we analyse its makeup, we find that it has
• 21:06
  DNA like Earth, DNA that has a shared
• 21:09
  universal common ancestor. And what that
• 21:12
  suggests is that once life gets started
• 21:13
  somewhere, it's transmissible. You know,
• 21:16
  you've got that old thing of don't go near
• 21:17
  Earth, it's got humans, they're contagious.
• 21:20
  This is the same kind of idea. If we find
• 21:22
  life on Mars and that life has a shared
• 21:24
  heritage with life on Earth, that
• 21:27
  validates strongly support c idea of
• 21:29
  panspermia, which I've had a student just
• 21:32
  submit his PhD thesis studying the
• 21:35
  idea that life can transfer between the
• 21:36
  planets. Now, again, if life can transfer
• 21:39
  easily enough to be found in multiple
• 21:40
  locations in the solar system from a simple
• 21:43
  single origin and, uh, maybe even Earth, uh,
• 21:45
  wasn't that origin. You know, maybe we're
• 21:47
  Martians, maybe we're Venusians or Venerians.
• 21:50
  I think that Venerian used to be the
• 21:52
  adjective for Venus. Adjective, the right
• 21:53
  word, used to be the word for Venus in the
• 21:55
  way that Martian was for Mars, but it was a
• 21:57
  bit too close to venereal, um, because.
• 22:01
  So they changed it. But anyway, um, but we
• 22:03
  could be venereal creatures. Um, we don't
• 22:05
  know. But what that suggests is that if life
• 22:07
  is transferred easily and effectively once it
• 22:10
  originates, life could be coming in the
• 22:12
  universe. So to me, finding life in the solar
• 22:15
  system would be awesome. I think it's
• 22:16
  eminently feasible. And either way, it will
• 22:19
  shed new light on the commonality of life
• 22:21
  beyond the solar system. We will be looking
• 22:24
  for life like us. It is possible to imagine
• 22:27
  life that is not like us, that has different
• 22:28
  requirements, but that will probably be a bit
• 22:30
  harder to find and we don't know
• 22:33
  what it would be. Whereas with life like us,
• 22:36
  we know things to look for. So that makes it
• 22:38
  a bit easier for us to look for life like us.
• 22:40
  It also makes it, I'd say,
• 22:43
  a little bit stronger as a case when you're
• 22:45
  asking for funding because you can say, well,
• 22:47
  we already know this kind of life can exist,
• 22:50
  so we're going to look at a place where the
• 22:51
  conditions are similar to where we know it
• 22:53
  does exist and, um, see if we find it there
• 22:54
  as well.
• 22:55
  Andrew Dunkley: Okay, let's take a short break. Uh, this
• 22:58
  is Space Nuts with Andrew Dunkley and
• 23:01
  Professor Jonty Horner.
• 23:05
  Yeah, I'm going to step off the
• 23:06
  Jonti Horner: lamb now
• 23:09
  that's one small step for man,
• 23:14
  one giant leap for man.
• 23:17
  Space nuts.
• 23:19
  Andrew Dunkley: It's not Professor Fred Watson Watson at the
• 23:21
  moment. He's away. We've got Professor John
• 23:22
  T. Horner, and we're talking astrobiology in
• 23:25
  this little, uh, special edition.
• 23:28
  Um, one thing I heard in the news recently,
• 23:30
  and I think Fred Watson and I talked about it
• 23:32
  was, uh, you know, we've been talking about
• 23:34
  water. And if you want to find the people,
• 23:36
  find the water, that sort of thing. But there
• 23:38
  was one particular study that was, uh,
• 23:41
  recently released that says if you want to
• 23:43
  find the people, find the coal. What do you
• 23:45
  think of that theory?
• 23:47
  Jonti Horner: That's an interesting one. So that's the idea
• 23:49
  that, uh, if you want to find somebody to
• 23:51
  talk to, there needs to be something to fuel
• 23:53
  an industrial revolution. And again, this is,
• 23:56
  I think, science fiction sometimes. Does this
• 23:58
  really ask these really interesting questions
• 24:00
  of almost is the path that we
• 24:03
  have followed the one that everyone
• 24:06
  will follow? You know, because there's so
• 24:08
  much to some degree randomness in
• 24:11
  the things that have driven our knowledge
• 24:13
  and our development of things. You know, um,
• 24:16
  obviously a good example is a famous myth
• 24:18
  about penicillin that if, um, you leave your
• 24:21
  bread out and it goes mouldy, that makes your
• 24:22
  poultice more effective. Um, and that was an
• 24:25
  incredible scientific revolution driven
• 24:28
  by that discovery. There was.
• 24:31
  Who's to say other civilizations would have
• 24:33
  the same discoveries in the same order. Now,
• 24:36
  to advance, we have required advances in
• 24:39
  energy in order to allow us to better
• 24:42
  develop technology and develop the things
• 24:44
  that everything's made of. You know, if we
• 24:46
  didn't have anything that you could burn,
• 24:49
  it would be very, very challenging to smelt
• 24:51
  metal. If you couldn't smelt metal, how do
• 24:53
  you build electronics?
• 24:55
  Andrew Dunkley: You are spot on. That's exactly what the
• 24:57
  article was all about. And, uh, the
• 25:00
  bottom line was, uh, that because of the
• 25:02
  timing required, it lessens
• 25:06
  the likelihood of us finding, uh, people
• 25:09
  like us. It reduces the odds.
• 25:11
  Jonti Horner: And this is where there's a difference
• 25:14
  between the search for extraterrestrial
• 25:16
  intelligence and the search for life. So the
• 25:18
  search for extraterrestrial intelligence is
• 25:20
  like a subset of the search for life? Yeah,
• 25:22
  search for life is a search for bacteria as
• 25:25
  much as the search for, uh, communicative
• 25:27
  aliens. And there's been a lot of stuff
• 25:30
  written and discussed about whether
• 25:33
  evolutionary quirks have benefited us by
• 25:35
  being here. You know, in terms of we're a
• 25:37
  social communal animal that shares resources
• 25:39
  and shares learning. There have been other
• 25:42
  ones like that from Ant Colins. And I'm
• 25:43
  listening to a very Chill and very
• 25:46
  silly, um, lit
• 25:48
  rpg, I think would be the description of the
• 25:50
  genre series of books called Chrysalis at the
• 25:53
  minute, where a young boy who dies for
• 25:56
  reasons is reincarnated in the bottom born
• 25:58
  body of an ant. And it's a book about him
• 26:01
  as an ant and his life in the colony and
• 26:03
  stuff, and it's bonkers. But, um,
• 26:06
  you've got an advanced social species there
• 26:08
  and he finds ways, without too many spoilers,
• 26:11
  of giving them intelligence and what happens
• 26:12
  afterwards. There's a few species in the
• 26:14
  history of Earth that have that kind of
• 26:16
  communal sharing of information thing. We're
• 26:19
  the only ones that have achieved what we've
• 26:20
  achieved. Some arguments are that's down to
• 26:23
  the development of language and our ability
• 26:26
  to produce complex language, and also the
• 26:28
  opposable thumb being quite important. So
• 26:30
  there's a lot of stuff that there are many
• 26:33
  steps between the development of life and the
• 26:35
  development of intelligence. And, uh, the
• 26:38
  development of intelligence itself doesn't
• 26:39
  necessarily mean the development of
• 26:41
  technological intelligence. You know, a lot
• 26:43
  of discussions about all the things octopi or
• 26:45
  octopods or octopiddles, octopi could
• 26:48
  achieve if they lived for more than three
• 26:50
  years. And if they were a social animal,
• 26:52
  they've got incredible brands. We're learning
• 26:54
  more and more about some of the brain power
• 26:56
  that birds exhibit, but
• 26:59
  none of them have become technological
• 27:01
  intelligences. And the search for
• 27:02
  extraterrestrial intelligence is very much
• 27:05
  centred around a technology
• 27:08
  that allows civilizations to communicate with
• 27:10
  one another. That therefore is based on many
• 27:13
  prerequisites that lead to the development of
• 27:15
  the ability to broadcast your existence to
• 27:17
  the cosmos.
• 27:18
  The coal thing's interesting. I mean, I'm not
• 27:21
  sufficiently archaeologically
• 27:23
  minded to be able to
• 27:26
  say with certainty that without coal we
• 27:29
  wouldn't have got here. And, uh, the reason
• 27:30
  that I express caution on that coal and oil
• 27:33
  is that we have things that people burn for
• 27:35
  energy that are not coal and oil.
• 27:38
  And I think a lot of the smelting that was
• 27:40
  done, and I may be wrong on this because I'm
• 27:41
  not an archaeologist, I just picked bits up
• 27:43
  when my partner's watching Time Tim and
• 27:45
  things like that. She loves her archaeology,
• 27:46
  so I get a little bit of that as a very thin
• 27:49
  veneer. But I think a lot of this times when
• 27:51
  people smelted metals, talking about bronze
• 27:53
  and iron, they used wood or they used
• 27:55
  charcoal, which is a byproduct of burning
• 27:57
  wood.
• 27:58
  Andrew Dunkley: Yeah.
• 27:59
  Jonti Horner: So maybe it would be more challenging without
• 28:02
  the easy available energy of fossil
• 28:05
  fuels, without the easy available energy of
• 28:07
  coal, oil, gas, but it might be that
• 28:10
  that wouldn't be an insurmountable hurdle,
• 28:12
  but it would result in a different path being
• 28:13
  followed. You know, what would we get
• 28:16
  in terms of seam power if we were using wood
• 28:18
  and if we were using charcoal rather than
• 28:21
  other things? Would it lead to an earlier
• 28:23
  adoption of renewable energy in the form of
• 28:26
  wind power, which was actually being used for
• 28:28
  hundreds of years? You go back to Europe and
• 28:30
  you see the windmills people use and water
• 28:32
  mills peoples use. So I.
• 28:35
  I don't know whether.
• 28:38
  And this is a problem with all of
• 28:40
  astrobiology and it's a problem with a lot of
• 28:42
  the stuff that I'll talk about later, about
• 28:43
  what makes a planet more suitable or less
• 28:45
  suitable. People have this tendency to
• 28:48
  find something that is unusual about us.
• 28:51
  And there's a lot that's unusual about us. I
• 28:52
  mean, there's a lot that's unusual about me.
• 28:54
  And I hold my hand up about that. But they
• 28:56
  find things that are unusual. And, um,
• 28:59
  they say we are, as far as we know, unique in
• 29:01
  the cosmos. We are a technologically advanced
• 29:03
  civilization able to have this discussion.
• 29:06
  There has to be a reason that we're here.
• 29:09
  Everything that is unusual quite often gets
• 29:12
  held up as could this be the switch? If you
• 29:14
  didn't have this, we would not be here. And I
• 29:17
  tend to view them not as an on off switch,
• 29:19
  but as a slider. They're like. And again, a
• 29:22
  gaming analogy would be varying the
• 29:23
  difficulty on your game. Some games, it's
• 29:26
  very kind of on off, hard mode, easy mode.
• 29:28
  Others, particularly some of the role playing
• 29:30
  type games people play, have sliders for
• 29:33
  everything. And so you can change things to
• 29:36
  the nth degree to tweak the challenge
• 29:39
  level. And I think all of these things, like
• 29:41
  the existence of call that get proposed
• 29:44
  as being a boundary, as being
• 29:47
  something that would be a block if you didn't
• 29:48
  have it, are actually probably more like one
• 29:51
  of those sliders. They're things that can
• 29:52
  facilitate. But it's really interesting
• 29:55
  to discuss them because we don't know how big
• 29:57
  a filter they are. We don't know how big a
• 29:59
  hurdle they are without digging into it more.
• 30:02
  And the more we can suggest these things, the
• 30:04
  more we can narrow them down. But ultimately
• 30:06
  the only way we can finally test them is when
• 30:08
  we get a response to us, when we find
• 30:11
  technologically advanced life and
• 30:14
  then we learn about their heritage. What path
• 30:16
  did they follow? Did they invent fire
• 30:19
  before the wheel? Did they invent
• 30:21
  modern medicine before fire?
• 30:24
  And I've seen there's a fabulous
• 30:28
  famous old thread I don't know. It wasn't
• 30:30
  from Reddit, predates Reddit, but from one of
• 30:32
  the old messaging boards that talks
• 30:34
  about humans as the horror
• 30:37
  movie monsters of the universe. Because we
• 30:40
  always, in science fiction, all the monsters
• 30:42
  we face, all the aliens we face, are usually
• 30:44
  more something than us. And we overcome
• 30:47
  incredible odds to beat them. But this is
• 30:49
  taking the other perspective of another
• 30:51
  species kind of looking at us and going,
• 30:52
  those humans are terrifying. And it's listing
• 30:54
  all the ways we are. You know, we're an
• 30:55
  exhaustion hunter. We didn't beat things by
• 30:58
  speed or anything. We'd follow them until
• 31:00
  they died of exhaustion because we
• 31:03
  can go longer than they can. Where are you?
• 31:05
  They were saying, you know, it's the only
• 31:07
  intelligent technological species that, uh,
• 31:09
  invented amputation before painkillers.
• 31:12
  You know, we've got things like this that are
• 31:14
  very bizarre about us. And so that takes
• 31:17
  this perspective I've got of these things are
• 31:19
  a hurdle. And you develop things, you know
• 31:22
  that things are not on an off switch, but
• 31:24
  they're more of a slider. And the idea of
• 31:27
  will things naturally be developed in the
• 31:29
  same order? And turns it around and said,
• 31:31
  what would another species think looking at
• 31:33
  us? And I always find that really good fun.
• 31:35
  And it's effectively leads to the thing that
• 31:37
  humans are space orcs and where this
• 31:39
  terrible, terrifying, weird little species.
• 31:42
  And maybe that's what it'll turn out to be.
• 31:45
  Andrew Dunkley: Well, yeah, look, uh, I don't
• 31:48
  dispute that because look how we treat each
• 31:51
  other or have treated each other,
• 31:53
  um, since civilization began,
• 31:55
  basically. I don't think you could add up
• 31:58
  how many wars we've fought against each
• 32:00
  other. I
• 32:03
  don't think that would stop. If we found
• 32:05
  another intelligent life form, I don't think
• 32:07
  we'd go in saying, hi, hey, we're really
• 32:09
  nice. I got a feeling we'd, you know,
• 32:12
  there'd be a bit of adversarial.
• 32:15
  Jonti Horner: It's a really, it is a really interesting
• 32:17
  one.
• 32:17
  It's one of the things that people factor
• 32:19
  into a lot of the discussions about the, the
• 32:22
  rights and wrongs of active seti.
• 32:25
  So active SETI is sending out a message
• 32:27
  saying, hi, we're here. Please talk to us.
• 32:29
  Whereas passive SETI is listening for people
• 32:31
  saying, please turn neighbours off. We're
• 32:33
  sick of seeing it. You know, they're
• 32:34
  effectively the two ways you can do seti.
• 32:37
  There are, uh, a lot of people in the past
• 32:39
  that have argued that active set is a bad
• 32:41
  idea because it will attract the wrong kind
• 32:42
  of attention. Well, Stephen Hawking certainly
• 32:45
  thought that, um, and throwing
• 32:47
  noshead. I think the great Mark Commode,
• 32:49
  who's a film reviewer in the uk, um, often
• 32:52
  says, you know, uh, other opinions are
• 32:54
  available. They're wrong, but they are
• 32:56
  available. I mean, this, I think, is a case
• 32:58
  of that. I think, if any, for me, and I will
• 33:01
  admit I'm an optimist, I'm also not exactly
• 33:03
  the world's most aggressive person. But for
• 33:06
  me, if you have survived as a species for
• 33:08
  long enough to be a thriving civilization to
• 33:11
  the point of wanting to communicate to the
• 33:12
  upscale upstarts that are broadcasting, you
• 33:15
  know, Big Brother and all the rest of it, to
• 33:16
  the universe, that suggests that to some
• 33:19
  degree you've overcome your martiality. Um,
• 33:22
  because I think for us to survive to the
• 33:25
  point where we're moving out into the stars
• 33:27
  will require us not to first wipe ourselves
• 33:29
  out. And the more advanced you get, the more
• 33:32
  you disperse, probably, fingers crossed,
• 33:35
  hopefully, the less likely that becomes. Now,
• 33:37
  we look at the world around us today, and
• 33:39
  without digging into politics, there's always
• 33:40
  something nasty going on. There's many, many
• 33:43
  tragedies that are both frontline in the news
• 33:45
  and forgotten by the news. But
• 33:48
  I saw a great article a few years ago
• 33:51
  that was arguing that, you know, when was the
• 33:53
  worst time to ever live, and saying that
• 33:54
  actually, despite the fact that all this war,
• 33:57
  all this aggression, all this violence is so
• 33:59
  front and centre, this is actually the safest
• 34:02
  era to live in that humanity's ever
• 34:03
  experienced. The number of people dying
• 34:06
  before their time, dying before they reach
• 34:08
  senescence, is lower per thousand people, up
• 34:11
  a hundred thousand people than ever before.
• 34:14
  You have a much lower chance as an average
• 34:16
  person of ever fighting in a war, of ever
• 34:18
  being murdered or assaulted. So
• 34:20
  we're already moving that way if it doesn't
• 34:22
  feel like it. And so to me, with that
• 34:25
  optimistic viewpoint, I would like to
• 34:27
  think that there is no reason for conflict
• 34:30
  and no reason for friction. And I think a lot
• 34:32
  of the arguments that humanity's, uh, future
• 34:35
  encounters with aliens must by necessity be
• 34:38
  violent is telling you more about people than
• 34:41
  it's telling you about aliens. Because it's
• 34:42
  saying when we look in the mirror, we see the
• 34:44
  angry, snarling, tribalist ape rather than
• 34:47
  the rational modern human that is a
• 34:49
  veneer. On m top. We're still a tribal
• 34:52
  species, we're still the product of our
• 34:55
  evolution and society is a veneer that we put
• 34:57
  on top of that as we learn, um, to be
• 35:00
  better, to be the kind of thinking social
• 35:02
  app, I guess. And the
• 35:05
  evidence is that over time we're getting
• 35:06
  better at that. Even though we're now more
• 35:08
  capable of killing each other than we ever
• 35:10
  were before. Yeah. We're doing it less often.
• 35:13
  Andrew Dunkley: Yes, we are.
• 35:14
  M. All right, we'll take a quick breather
• 35:16
  because I want to get into the, um, the
• 35:19
  area of, um, finding this
• 35:22
  life beyond our solar system. How, how are we
• 35:25
  going to. At where we're going to look and
• 35:26
  Jonti Horner: what we've got to look for.
• 35:27
  Andrew Dunkley: That's all coming up on this edition of Space
• 35:30
  Nuts.
• 35:35
  Jonti Horner: Space Nuts.
• 35:36
  Andrew Dunkley: So, Jotty, look, lead the way. Where do you
• 35:38
  want to go from here? We're gonna, uh, this
• 35:40
  is our final segment.
• 35:41
  So, um, I suppose if you're going to try and
• 35:44
  find life beyond our solar system,
• 35:48
  uh, you've got to find the right environment.
• 35:50
  Um, you know, rocky planet, habitable zone,
• 35:53
  perhaps. Um,
• 35:56
  and there's a lot more to it than that. It's
• 35:58
  not just, uh, a planet with perhaps liquid
• 36:00
  water on its surface. Uh,
• 36:04
  you've got to have, I suppose, the right kind
• 36:05
  of star. You don't want a red dwarf because
• 36:08
  you probably just, you know, get really bad
• 36:10
  sunburn. Uh, there's a lot to take
• 36:12
  into account.
• 36:14
  Jonti Horner: There's a huge amount of depth to it. And I
• 36:15
  think, as we saw with the previous episode,
• 36:18
  we could have talked another hour and we
• 36:20
  could have talked another week. To be honest,
• 36:21
  when we're talking about this stuff, one of
• 36:23
  the things I, I most adore about
• 36:25
  science is the infinite complexity. So you
• 36:28
  ask a question, when you get an answer that
• 36:30
  isn't it. But you get another 10 questions
• 36:32
  and the more you know about a subject, the
• 36:34
  more complexity there is. To me, that's just
• 36:36
  a wonder. And that's fascinating and this is
• 36:38
  a really good example of that. Now, one of my
• 36:42
  strongest arguments through my career
• 36:46
  has been that we can't just, when we're
• 36:49
  trying to think about where we're going to
• 36:50
  search for life beyond the solar system, use
• 36:52
  a habitable zone. Um, and that's it. You
• 36:54
  know, it seems like a lot of coverage and a
• 36:57
  lot of papers just go, Earth, like planet
• 36:59
  found in the habitable zone.
• 37:00
  Andrew Dunkley: Whee.
• 37:01
  Jonti Horner: And ah. And um, that's about it. Now the
• 37:04
  habitable zone has become a really effective
• 37:06
  communication tool in much same way the Drake
• 37:08
  Equation has. The Drake Equation is this
• 37:11
  fabulous tool with all the sliders where you
• 37:12
  can make your own, um, inhabited universe
• 37:15
  with lots of few aliens by varying the
• 37:17
  variables. The habitable zone has become
• 37:20
  another of these catch all kind of
• 37:22
  visualisations. And it's born of the idea
• 37:24
  that life needs liquid water with the
• 37:26
  implicit extension of that, that life needs
• 37:29
  liquid water on a planet's surface.
• 37:32
  Now, that's initially motivated by the fact
• 37:34
  that the Earth is the only place with life
• 37:36
  and back when this was being discussed, the
• 37:38
  only place with liquid water that we knew. So
• 37:41
  therefore it was natural to say you need
• 37:42
  surface liquid water. As we discussed
• 37:45
  earlier, there are plenty of places in the
• 37:46
  solar system that do not have liquid water on
• 37:48
  the surface, but do have it underneath.
• 37:50
  They've got soft centres. But the habitable
• 37:53
  zone, um, says you need liquid water
• 37:56
  on the surface of a planet for that planet to
• 37:58
  be considered suitable for life to be
• 38:00
  habitable. Now, that isn't entirely
• 38:03
  true, but for the purposes of this, it's
• 38:05
  still useful because life buried beneath
• 38:08
  ice is so hard to find that we can't find it
• 38:10
  in our own solar system. Because the ice is
• 38:12
  in the way, we wouldn't have a chance to run
• 38:14
  planets around other stars. So even though I
• 38:16
  think the habitable zone is a bigger
• 38:18
  oversimplification, I see merit to it,
• 38:20
  because life on a planet's surface with
• 38:22
  only atmosphere above is much more likely to
• 38:25
  be detectable than life buried deep in the
• 38:27
  interior. So, fair enough, we'll go with it.
• 38:29
  The idea of the habitable zone, though, is
• 38:31
  that the closer you are to a star, the hotter
• 38:33
  you are, the further away you are, the cooler
• 38:35
  you are. And just like Goldilocks and the
• 38:37
  Three Bears, which is why it's often called
• 38:39
  the Goldilocks Zone, there's a place where
• 38:40
  it's just right, it's not too hot, not too
• 38:42
  cold, and therefore there could be liquid
• 38:44
  water on the surface of the planet. Now, a
• 38:47
  lot of the time when people say a planet is
• 38:49
  in the habitable zone, um, that's
• 38:52
  often taken as meaning that planet could and
• 38:55
  potentially will have liquid water on the
• 38:57
  surface. But actually, what it's saying is,
• 38:59
  if you took the Earth as the Earth is today,
• 39:02
  and put it in that system, would it still
• 39:05
  look like the Earth? Would it have liquid
• 39:06
  water on its surface? Now, now
• 39:09
  we've extended a bit beyond that. There are a
• 39:11
  couple of fabulous papers a bit more than a
• 39:13
  decade old now that set. What are our very,
• 39:15
  uh, contemporary scientific, mathematical
• 39:17
  definitions of the habitable zone, um, that
• 39:19
  people use for their papers, and they take
• 39:22
  the flux from the star, take into account the
• 39:24
  different colours of the stars and, um, there
• 39:27
  are two versions. There's the optimistic and
• 39:29
  conservative versions, where the
• 39:31
  optimistic version is a wider set of
• 39:34
  distances and the conservative version is a
• 39:35
  smaller set of distances, but it effectively
• 39:38
  uses Venus and Mars as A roughinger edge in
• 39:40
  our solar system and then scales that window
• 39:42
  up and down depending on the kind of star
• 39:44
  you're around. But that illustrates
• 39:47
  immediately that this is an
• 39:49
  oversimplification, because you can do a
• 39:51
  thought experiment. Let's take our solar
• 39:53
  system. Venus is way too hot, Mars is way too
• 39:56
  cold and the Earth is just right. All well
• 39:58
  and good. Swap the Earth. Sorry, swap Mars
• 40:01
  and Venus around. If you put Venus where Mars
• 40:03
  is, Venus's thick atmosphere and greenhouse
• 40:06
  effect would mean it'd be warming up liquid
• 40:07
  water on the surface. It wouldn't have cooled
• 40:09
  as much as Mars. So Venus will be
• 40:12
  habitable on the surface, outside the
• 40:14
  habitable zone. Um, if you put m Mars, where
• 40:17
  Venus is, with its very thin and tenuous
• 40:18
  atmosphere, it doesn't have much greenhouse
• 40:21
  effect at all. Mars would potentially still
• 40:24
  be habitable where Venus is, when
• 40:27
  Venus isn't. And so that's immediately
• 40:29
  pointing that the storey is actually
• 40:31
  significantly more complex. Yeah. That
• 40:34
  you can't just say, let's calculate the
• 40:37
  habitable zone, let's calculate the
• 40:38
  equilibrium temperature on a planet, which is
• 40:41
  a temperature it would have if it didn't have
• 40:44
  a greenhouse effect, that it was a certain
• 40:46
  reflectivity and it was in equilibrium with
• 40:48
  the light coming in and light coming out. And
• 40:50
  if that temperature is from about minus 20
• 40:52
  upwards, it's probably warm enough for water
• 40:54
  because, well, you'll have a bit of an
• 40:55
  atmosphere. To me, that's never been enough.
• 40:58
  Now, the reason it's really important, at
• 41:00
  least from my perspective, is that, uh,
• 41:03
  finding planets is hard. We'll talk about
• 41:05
  that in another episode. But once you find
• 41:08
  the first of something, astronomy, history
• 41:11
  and probably every other form of scientific
• 41:12
  endeavour history tells us finding the first
• 41:14
  of something is hard. But once you've got
• 41:16
  one, you quickly find more and more as your
• 41:18
  technology gets better. Finding evidence of
• 41:20
  life on a planet that is similar to the Earth
• 41:24
  is fundamentally at least an order of
• 41:26
  magnitude, if not more harder than finding
• 41:29
  that planet was. So it'll take time for our
• 41:31
  technology to get good enough to search
• 41:33
  comfortably for life elsewhere. So initially
• 41:36
  that search is going to be very restricted
• 41:38
  because we've got limited resources. So
• 41:40
  you're only going to be able to look at a few
• 41:42
  planets aggressively at first, to try and
• 41:45
  tease out any indication of life.
• 41:47
  But you're going to have loads to choose
• 41:49
  from. How should you choose? Well, to me, it
• 41:52
  can't just be the habitable zone.
• 41:56
  Andrew Dunkley: Yeah, that's a valid point. Um,
• 41:59
  and we've reached a point where we've found
• 42:02
  thousands upon thousands of Exoplanets and
• 42:04
  counting like we haven't stopped. We're
• 42:06
  finding them more and more and more often of
• 42:09
  all different shapes of, uh, sizes. Um,
• 42:13
  some rocky planets, uh, they've been harder
• 42:16
  to find because they're usually much smaller
• 42:18
  and don't sort of indicate
• 42:21
  themselves like a gas giant does.
• 42:24
  But we're getting better at finding rocky,
• 42:26
  uh, planets.
• 42:27
  Um, I suppose the big
• 42:30
  question is, given how much we are finding,
• 42:34
  how do you identify prime targets for life?
• 42:37
  Jonti Horner: Yeah, and that is what the paper that I put
• 42:40
  together with Barry Jones back in 2010 was
• 42:42
  all about. So Barry was a very dear friend of
• 42:45
  mine. He was my boss when I moved to the open
• 42:47
  University from 2000 and 22,006 to 2009. I
• 42:49
  think he knew Fred Watson very well as well.
• 42:50
  So you can always mention to Fred Watson that
• 42:52
  we talked about Barry. I started work at the
• 42:54
  Open University in 2006 on the day Barry was
• 42:57
  forced to retire by the government because
• 42:59
  he'd hit 67. So he hired me and promptly
• 43:02
  retired. But, um, he kept working anyway as
• 43:04
  emeritus professor and Barry and I
• 43:07
  did a lot of work on this during my time that
• 43:09
  Barry unfortunately passed away a little bit
• 43:11
  more than a decade ago. So he's fondly
• 43:13
  remembered. I organise a, an award in the UK
• 43:15
  in his memory every couple of years. What
• 43:18
  we did in this 2010 paper was
• 43:22
  to essentially have the thought process we
• 43:24
  just outlined. So we're going to have a huge
• 43:27
  number of potential exo Earths, planets that
• 43:29
  could potentially be Earth like that could be
• 43:32
  places to look for life. But we're only going
• 43:35
  to be able to search a, ah, handful of them
• 43:36
  initially. So what should we do to select the
• 43:39
  best target? Now obviously the
• 43:41
  closer the planet's host star is to the solar
• 43:44
  system, the easier the observations will be.
• 43:46
  That's just a fundamental thing of if you're
• 43:49
  twice as far away, we only receive a quarter
• 43:50
  as much light from you. But also if you're
• 43:53
  twice as far away, the separation between the
• 43:55
  planet and the star on the sky will be half
• 43:57
  as much because the angle gets
• 44:00
  smaller the further away you go. Essentially
• 44:02
  we, uh, will want targets that are far enough
• 44:03
  from the star in the sky that with future
• 44:05
  missions like potentially the Habitable
• 44:06
  Worlds Observatory, we can separate the light
• 44:09
  from the planet from the light from the star.
• 44:11
  So probably even more important than the
• 44:14
  habitable zone, um, is this proximity thing.
• 44:16
  The planets in the main found by the Kepler
• 44:19
  space telescope won't be suitable for this
• 44:21
  search because they're mainly very far from
• 44:23
  the sun. And so therefore they'll be very
• 44:26
  hard to study. We want to look locally,
• 44:27
  that's a given. But
• 44:30
  we want to look for places where there is the
• 44:32
  possibility of liquid water on the surface
• 44:35
  because that means that the life will be in
• 44:37
  contact with the atmosphere and that might
• 44:38
  generate a signature we can detect in the
• 44:40
  atmosphere. And that's where the habitable
• 44:42
  zone comes from. But there's actually much
• 44:45
  more to it than that, I think, and I'm far
• 44:47
  from able to give an exhaustive list because
• 44:48
  I'm not an expert in, uh, all areas of
• 44:51
  astronomy. But we decided to put together a
• 44:53
  review paper which, about 32
• 44:56
  pages long, probably a little bit outdated
• 44:59
  now because science has moved forward, but
• 45:01
  was saying, effectively you can't just use a
• 45:04
  habitable zone. We need to think about
• 45:07
  all of the different factors that can
• 45:09
  contribute to make a planet more or less
• 45:10
  suitable for life. Now, many of these have
• 45:13
  been in the past suggested as that on off
• 45:15
  switch. And I do think that they're more
• 45:17
  sliders, like the numbers in the Drake
• 45:18
  equation or sliders on a mixing desk. But
• 45:21
  there are a lot of different things that have
• 45:22
  been suggested and as I dug into the paper,
• 45:25
  there were even more than I thought of. You
• 45:26
  can broadly break them down m into four
• 45:29
  areas. The first is galactic influences.
• 45:32
  So the impact of the galaxy itself, where you
• 45:35
  are in the galaxy, stuff like that, you've
• 45:37
  then got stellar influences, so the role of
• 45:39
  the star. You've got the planetary system and
• 45:42
  then you've got the planet itself. So they're
• 45:44
  the kind of four broad areas, the
• 45:46
  galactic influences. One is probably the
• 45:49
  least useful and the least well constrained.
• 45:50
  But the idea of the galactic influence is
• 45:53
  tied a bit to a theory that's been put
• 45:55
  forward by a few people called the Galactic
• 45:57
  Habitable Zone. It's an idea that
• 46:00
  ties back to the origin of stars and planets
• 46:03
  and also to the dangers that are experienced
• 46:05
  because of your environment. The idea that as
• 46:07
  time goes on, the universe is becoming more
• 46:09
  metal rich and by that I mean enriched in
• 46:12
  everything other than hydrogen and helium,
• 46:14
  because generations of stars run their
• 46:16
  furnaces and turn the light elements to the
• 46:18
  heavy ones and put them back into the cosmos.
• 46:20
  You need a certain amount of heavy elements
• 46:22
  to form planets like the Earth and to have
• 46:24
  the carbon, nitrogen, phosphorus for life.
• 46:27
  So as time goes on, the universe getting more
• 46:29
  enriched is a good thing. But there's also
• 46:32
  possibilities that too much enrichment will
• 46:34
  change the chemistry or it will make planet
• 46:36
  formation too easy. There's all sorts there,
• 46:38
  so you might have a sweet spot from that side
• 46:40
  of things. Now in the middle of the galaxy,
• 46:43
  star formation occurs at a more rapid pace
• 46:46
  and stars live and die quicker. So you get
• 46:48
  faster change in the abundance of
• 46:51
  materials. So you can imagine we have this
• 46:54
  concept in astronomy called metallicity,
• 46:56
  which is the amount. It's usually measured in
• 46:58
  the amount of hydrogen compared to the amount
• 47:00
  of iron in a star. And that gives you a
• 47:03
  number on a logarithmic scale. And that is an
• 47:05
  approximation to when the star formed and how
• 47:08
  enriched the world was at the time. And as
• 47:10
  time goes on, things get more and more metal
• 47:12
  rich within our galaxy. You'd expect there to
• 47:14
  be a gradient in this, so the things near the
• 47:16
  middle will be much more enriched in heavy
• 47:18
  elements of things, things near the outer
• 47:19
  edge. And there's probably sweet spot in the
• 47:21
  middle that moves outwards over time where
• 47:24
  conditions to form planets like the Earth,
• 47:26
  uh, and planetary systems like the solar
• 47:27
  system are perfect. So that's part of the
• 47:30
  galactic habitable zone idea. But the other
• 47:32
  idea is that if you're too close in and the
• 47:35
  stellar density is too high, eventually the
• 47:37
  stellar density gets, uh, so high that the
• 47:39
  likelihood of life being exterminated by
• 47:41
  nearby supernovae or planetary systems being
• 47:43
  stripped and disrupted becomes too high. So
• 47:46
  there's always been this idea that location
• 47:48
  within the galaxy is important.
• 47:51
  The challenge to that is twofold. Firstly,
• 47:54
  the proximity argument. We're gonna have to
• 47:56
  look at stars that are very nearby, which are
• 47:59
  all at the same distance from in the middle
• 48:00
  of the galaxy as we are. So where you are in
• 48:03
  the galaxy won't realistically impact this
• 48:06
  search because we're going to be looking
• 48:07
  locally. The other thing so is that stars
• 48:10
  have a huge degree of mobility. There was a
• 48:12
  recent storey talking about finding solar
• 48:14
  twin stars that have the same chemistry as
• 48:16
  the sun, that may have formed with the sun,
• 48:19
  and a suggestion that the sun and other stars
• 48:22
  may have formed as much as 10,000 light years
• 48:24
  nearer the middle of the galaxy than we are
• 48:26
  now. Stars are getting scattered inwards and
• 48:28
  outwards. So seeing a star here now doesn't
• 48:30
  imply that it's always been here.
• 48:33
  Andrew Dunkley: Yeah.
• 48:33
  Jonti Horner: So the galactic influences, I'm not going to
• 48:36
  go into really any more than that, but it's
• 48:38
  worth knowing that they're there, there. It's
• 48:40
  worth knowing that it's a point of discussion
• 48:41
  and that there is good research going on
• 48:42
  about this. It's really interesting area, but
• 48:45
  it doesn't, I think, impact our initial
• 48:47
  search for life, because we're going to be
• 48:50
  searching our local area. So it's a bit like
• 48:52
  me saying, I Want to search for signs of life
• 48:54
  on Earth, It's a lot easier for me to search
• 48:57
  in Kingstorp, where I live, than to search in
• 49:00
  Mumbai or in London. Places like this,
• 49:02
  you've got to look locally. Now, talking
• 49:05
  about that, you know, what would I expect to
• 49:06
  find? I'm, you know, the people in Kingsop
• 49:09
  have not all, but many of them have a similar
• 49:11
  background to me, formed in similar ways with
• 49:13
  similar cultural, the rest of it. So
• 49:16
  this is not a great analogy, I
• 49:18
  admit, but we've got to look locally. So the
• 49:20
  galactic influencer stuff is
• 49:23
  interesting, but I wouldn't say it
• 49:26
  is a big factor, but it's worth. Okay, I
• 49:28
  guess.
• 49:30
  Andrew Dunkley: So that leads us on to,
• 49:32
  um, I don't know, finding the right
• 49:35
  targets. Uh, and, and if we do find
• 49:38
  those targets, what, what do
• 49:41
  we do then to look for potential
• 49:43
  life on those targets?
• 49:45
  Jonti Horner: Absolutely. And that's a very hard question.
• 49:47
  Now, in terms of finding the right targets,
• 49:48
  there's a lot that comes into it from the
• 49:50
  star itself. Now,
• 49:53
  stars live very long lives.
• 49:56
  First question then is, how old is a star?
• 49:58
  Now, if we look at life on Earth, the oldest
• 50:00
  star fossils on Earth that are widely
• 50:02
  accepted are about three and a half thousand
• 50:04
  million years old, are in the Pilbara, which
• 50:06
  is about a billion years after the Earth, uh,
• 50:08
  formed. There are some that are older that
• 50:10
  are still controversial, possibly as old as 4
• 50:13
  billion years. But if we take the 3 1/2
• 50:14
  billion years as a threshold and we do what
• 50:17
  we're doing with the liquid water thing, and
• 50:19
  we say we expect life to follow a similar
• 50:20
  path, to us, the fact that it took a billion
• 50:23
  years for life to get established enough to
• 50:25
  leave fossils we could find possibly means
• 50:27
  that it might have taken a similar length of
• 50:29
  time for that life to modify its environment
• 50:30
  enough to be detectable from elsewhere. So we
• 50:33
  can put an arbitrary kind of timer here
• 50:35
  saying that any planetary system younger
• 50:38
  than, say, a billion years may have planets
• 50:41
  that are suitable for life, but that life
• 50:42
  might have not had enough time to get
• 50:44
  established yet. So that might
• 50:47
  immediately say that's not as good a place to
• 50:50
  look as a star that is more like the edge of
• 50:51
  the sun, while life's had 4 billion years to
• 50:54
  get going. Now, tied to that is
• 50:56
  the fact that the lives of stars are very
• 50:59
  dependent on the mass. So the more massive a
• 51:01
  star is, the brighter it shines, but the
• 51:03
  shorter its life is. And at a very rough
• 51:06
  level, this number varies a little bit
• 51:08
  depending on the mass of the star. But
• 51:09
  typically, the luminosity of a star Is
• 51:12
  proportional to its mass to the power four.
• 51:14
  So if you've got a star that is 10 times the
• 51:16
  mass of the sun, it will be roughly 10,000
• 51:18
  times brighter than the sun. But these
• 51:20
  stars are burning their own material. They're
• 51:22
  turning hydrogen to helium, and they're made
• 51:24
  of hydrogen. So a star that is 10 times the
• 51:26
  mass of the sun will only have 10 times as
• 51:28
  much fuel as the sun, but it's burning that
• 51:31
  fuel 10,000 times quicker, which means it'll
• 51:33
  run out a lot quicker. And what that means is
• 51:36
  that, uh, the more massive a star is, the
• 51:37
  longer, the shorter its life will be. And the
• 51:40
  less massive a star is, the longer its life
• 51:42
  will be. That means that beyond
• 51:45
  a certain, uh, stellar mass, the star will
• 51:47
  die before that billion year cutoff. So we
• 51:50
  can probably rule out the most massive stars.
• 51:52
  They'll just live fast, die young, and it's
• 51:54
  unlikely that life will get well enough
• 51:55
  established. On the flip side, the dim little
• 51:58
  red dwarfs will just go forever. You know,
• 52:00
  Proxima Centauri will still be trundling
• 52:02
  along in a trillion years when we're a decent
• 52:03
  memory. So they might be a good place to
• 52:06
  look. The challenge there though is, uh,
• 52:08
  those stars are, uh, quite active quite
• 52:11
  often. And um, to be in the habitable zone
• 52:13
  around them, you've got to be very close in
• 52:15
  because they're called little embers. You've
• 52:16
  got to snuggle up to the fire. So there's a
• 52:18
  lot of discussion about the fact that m dwarf
• 52:20
  planets, planets around these coolest,
• 52:22
  smallest stars are probably not ideal places
• 52:25
  to look for knife initially, few reasons. One
• 52:27
  is that activity and a lot of discussions
• 52:29
  that the activity of red dwarfs when they're
• 52:31
  young could scour a planet's atmosphere away.
• 52:33
  And that seems to have possibly been backed
• 52:35
  up with the Trappist 1 planets that all seem
• 52:38
  to be airless worlds. The other is that those
• 52:41
  planets, if they are close enough in to be
• 52:43
  warm enough for liquid water on the surface,
• 52:45
  would have to be tidally locked like the moon
• 52:47
  is to the Earth. Which means they'll keep one
• 52:49
  face permanently pointed towards the star and
• 52:51
  the other permanently away, which may make it
• 52:54
  harder to look for life on them. It might be
• 52:56
  the case, uh, any life would be on the
• 52:57
  sunward side. And that's kind of hard to
• 52:59
  observe because when that side is best
• 53:01
  presented to us, it's near the star. So
• 53:04
  that's challenging. Another thing that
• 53:06
  factors into it ties into something called
• 53:08
  the faint early sun paradox on Earth.
• 53:11
  The lives of
• 53:13
  stars. They shine brightly, their brightness
• 53:16
  Is measured good compared to their mass, but
• 53:18
  their brightness increases with time. Stars
• 53:20
  get more luminous as they age a little bit,
• 53:22
  and it's a slow process. But with the sun,
• 53:25
  we think the sun was 30 dimmer
• 53:28
  when it was born to how it is now. So
• 53:31
  that means the Earth at the time got 30% less
• 53:33
  energy, which would have put it, with its
• 53:35
  current atmosphere, too cold to support
• 53:38
  life. Um, that was offset by the
• 53:41
  fact we had a very different atmosphere than
• 53:43
  in a significant greenhouse effect,
• 53:46
  which was lessened due to the influence of
• 53:48
  life stripping out carbon dioxide,
• 53:51
  particularly from the atmosphere, and keeping
• 53:53
  us mostly there and thereabouts. But what
• 53:55
  that means is that if we find a planet now
• 53:58
  and that planet is near the outer edge of the
• 54:00
  habitable zone, um, everybody will go, well,
• 54:02
  it's in the habitable zone. That's great.
• 54:04
  Whereas my question would then be, but how
• 54:06
  long has it been in the habitable zone?
• 54:08
  Because when the SAR was younger, it was a
• 54:10
  little bit dimmer. The habitable zone would
• 54:13
  have been closer in, and that planet might
• 54:14
  well have been outside it. So I don't
• 54:16
  necessarily think that that 1 billion year
• 54:18
  clock would start until the planet was in the
• 54:20
  habitable zone. So we'll probably then be
• 54:22
  able to rule some planets out on the
• 54:25
  basis of the fact that they could be
• 54:28
  in the habitable zone, uh, now, but they
• 54:29
  haven't been full long enough. Yeah, the star
• 54:32
  has all these effects. Never mind the fact
• 54:34
  that astronomers often joke that three out of
• 54:36
  every two stars are in a multiple star
• 54:38
  system. Them multiple, um, stars are
• 54:41
  very, very common. And uh, that adds a whole
• 54:43
  extra level of complexity, Both to
• 54:46
  the understanding of the lives of the planets
• 54:48
  in those stars, but also in our ability to
• 54:50
  study them. Because you've got more than one
• 54:52
  stars like to factor rain all close together.
• 54:55
  It's much nastier and much more complicated.
• 54:58
  So there's a lot of ways that the stars can
• 55:00
  factor in. And I think that's only a, ah,
• 55:02
  very, very broad brushstrokes view, but
• 55:04
  you can see how. So what I'm thinking is you
• 55:07
  can bring in all these different ideas and
• 55:10
  halve them as a slider. This kind of star
• 55:13
  could have planets around it with life, but
• 55:14
  it's not as good a target as this one. Now,
• 55:17
  everybody could build their own algorithm out
• 55:19
  of this, But I'd like to think that when
• 55:20
  we're trying to pick the target, you take
• 55:22
  into account the star that it's going around,
• 55:25
  how active it is. Is it a single star, Is
• 55:28
  it old enough, all these kind of factors
• 55:31
  and Then you can start looking at the
• 55:33
  planetary system that it's in. And there's a
• 55:35
  lot to talk about there, I think.
• 55:37
  Andrew Dunkley: Yes, absolutely. Uh, and in
• 55:40
  our next, um, ah, special,
• 55:43
  um, between Q and A episodes, we will,
• 55:46
  um, look more into, um, the, the
• 55:49
  planet side of things.
• 55:50
  I, I guess just to conclude, um, I'll throw
• 55:53
  one at you. Um, and, and this answer is
• 55:56
  always different, depending on who you ask.
• 55:58
  But, uh, we. What do you think the odds are
• 56:00
  that we will find some form of life?
• 56:05
  Jonti Horner: I'm an optimist. I think the answer to
• 56:08
  it will be yes, we will find some sort of
• 56:10
  life. I think the harder question is when?
• 56:13
  Now, if we find life in
• 56:16
  a million years time when we're not even
• 56:18
  human anymore, but we've hung around, we've
• 56:19
  managed to survive. That's not very edifying
• 56:22
  for me and you because it's long time to
• 56:23
  work. But as I said earlier on, I don't think
• 56:25
  it's a question of if, it's a question of, of
• 56:27
  when. Because I find it vanishingly
• 56:30
  improbable for us to be the only
• 56:33
  system with life. And it's a numbers game for
• 56:36
  me. You know, we've got a galaxy with between
• 56:38
  200 and 400,000 million
• 56:40
  stars. There are more galaxies in the
• 56:43
  visible universe, certainly than there are
• 56:46
  planets in our galaxy, probably more than
• 56:49
  there are grains of sand in our galaxy. All
• 56:51
  of them with hundreds of thousands of
• 56:53
  millions of stars to say that
• 56:55
  out of. If you run the numbers, you get
• 56:58
  sextillions, septillions, even
• 57:00
  octillions bonkersly full
• 57:03
  on numbers of planets out there that
• 57:06
  were the only place that got life. That tells
• 57:09
  you that life is effectively impossible and
• 57:11
  we're a fluke. Now, that
• 57:14
  could be the case. If that's the case, what
• 57:16
  we've got here on Earth becomes even more
• 57:18
  precious. And there is an even greater
• 57:20
  incentive for us to keep an eye on what
• 57:23
  we're doing so that Earth is still capable of
• 57:25
  hurting life in the future. But I think in
• 57:28
  reality, life will actually be more common
• 57:30
  than that. And you don't need to be much more
• 57:32
  common than that for life to be abundant in
• 57:34
  the galaxy. Let's imagine that life is
• 57:37
  found on one planet in one
• 57:40
  billion. That's billion with a B. So one in a
• 57:43
  thousand million. Now we're finding that on
• 57:45
  average, all stars have planets, probably
• 57:47
  have a number of planets. So if we say
• 57:49
  roughly there are 10 planets per star, there
• 57:51
  will be 4,4 trillion planets in our galaxy.
• 57:54
  If one in a billion had life on
• 57:57
  it, that will mean there were 4,000 inhabited
• 58:00
  planets in our galaxy. Not a
• 58:03
  big number. The nearest one will be so far
• 58:04
  away. In that case we wouldn't find life for
• 58:06
  a long time. But life could be common
• 58:09
  and we still wouldn't find it. The more you
• 58:11
  increase that likelihood of life, the nearer
• 58:14
  uh, the nearest examples will be in, the
• 58:16
  sooner we'll find it. And that's why I think
• 58:18
  proximity will tell us a lot about the
• 58:20
  probability of life and that
• 58:23
  if we find life, the next step is to
• 58:26
  figure out we are not alone, we know we're
• 58:28
  not alone, how common is life. Now the other
• 58:31
  thing I think factors into it, I think is a
• 58:33
  lovely kind of sci fi thing to discuss all
• 58:35
  the way through. You mentioned early on
• 58:36
  carbon based life and technologically
• 58:39
  advanced life and we drifted away. The
• 58:42
  one place where I think that life that is
• 58:45
  different to us is something we could
• 58:46
  possibly find is silicon based life.
• 58:50
  Now the reason for that is not from
• 58:53
  the point of view of um, silicon
• 58:56
  people who have evolved in the way we have
• 58:59
  done. I'm thinking more kind of second
• 59:01
  generation life. Now our exploration of the
• 59:03
  solar system is done by our robot envoys and
• 59:06
  we're sending them near enough to harm that
• 59:08
  we can tell them what to do. But we are
• 59:11
  developing to certain controversy at the
• 59:14
  current time. We're developing a greater and
• 59:15
  greater ability to visualise, develop things
• 59:17
  that can make decisions for themselves
• 59:19
  without human input, things like AI and other
• 59:21
  systems. And if we get to the point where we
• 59:24
  want to explore around other
• 59:26
  stars, we'll need to develop spacecraft that
• 59:29
  have enough autonomy to make their own
• 59:31
  decisions. You go back to the idea and I
• 59:34
  don't know what's happened to it in recent
• 59:35
  years, but the idea of Project Starshot,
• 59:36
  where they made a little spacecraft, shot
• 59:38
  them off with laser, then they got to proxima
• 59:40
  Centauri in 25 years, travelling at a fifth
• 59:43
  of the speed of light. You do that,
• 59:46
  they get to Proxima Centauri. If they've got
• 59:48
  to ask us what to do, they send a signal to
• 59:49
  us. Takes four and a bit years to get here,
• 59:52
  takes five years to get back, and by the time
• 59:54
  it reaches them, they're a light year beyond
• 59:55
  the system and it's like, well too late. So
• 59:57
  we have to give them a certain level of
• 59:59
  autonomy. And the more complex their mission
• 1:00:01
  is going to be, the more autonomous it have
• 1:00:03
  to be. Which leads to uh, the very science
• 1:00:05
  fiction idea that when we move out beyond the
• 1:00:08
  solar system, if we move out beyond the solar
• 1:00:10
  system, we will be preceded by
• 1:00:13
  a wave of life that is not us,
• 1:00:16
  that is our life that has a
• 1:00:18
  creator. That creator is humanity. That is
• 1:00:21
  silicon based life that we send out, whether
• 1:00:23
  they're von Neumann machines, whether they
• 1:00:25
  are incredibly advanced AI machines without
• 1:00:28
  the capacity to reproduce themselves. We
• 1:00:31
  will send out artificially
• 1:00:34
  built silicon life forms. And again,
• 1:00:37
  that's a lovely, fairly lost X
• 1:00:40
  sci fi series called the Bobby Verse,
• 1:00:42
  um, which follows that kind of idea in terms
• 1:00:45
  of future Earth. Well, guy
• 1:00:48
  in the current day dies, but has invested in
• 1:00:50
  cryogenics and his head is frozen and he
• 1:00:53
  wakes up and he's essentially put into a Van
• 1:00:55
  Neumann machine and shot out into the stars.
• 1:00:58
  And that, that's a really interesting one
• 1:00:59
  because it's silicon based life that is also
• 1:01:01
  human. Let me figure that one out. But it's
• 1:01:03
  good fun following again that very
• 1:01:06
  dangerous assumption that other life would
• 1:01:08
  follow the same path where we follow. And it
• 1:01:10
  seems like we are going down this AI and
• 1:01:12
  increasing complexity and increasing autonomy
• 1:01:15
  route. You'd then argue that other species
• 1:01:18
  sending out craft into the galaxy
• 1:01:20
  would send out autonomous
• 1:01:23
  intelligent silicon machines
• 1:01:26
  before they send themselves out. And
• 1:01:28
  therefore, you know, I think we're more
• 1:01:30
  likely, if we're ever to bump into aliens, to
• 1:01:32
  run into one of these probes or one of these
• 1:01:34
  machines rather than the aliens themselves. I
• 1:01:36
  think there is a very real chance that if we
• 1:01:38
  find intelligent advanced life, it could be
• 1:01:41
  silicon based rather than carbon based. But
• 1:01:43
  it's silicon based life that was created by
• 1:01:45
  carbon based life, which I mean,
• 1:01:48
  leads to really interesting questions about
• 1:01:50
  philosophy and religion and all those kind of
• 1:01:52
  things which are not my forte. But you know,
• 1:01:54
  it does ask interesting questions about
• 1:01:56
  origin and creation when you think about it
• 1:01:58
  from the context of that, which is one of the
• 1:02:00
  things that driven, like I said, a lot of
• 1:02:02
  wonderful and wonderfully entertaining sci fi
• 1:02:04
  over the years.
• 1:02:05
  Andrew Dunkley: Yeah, yeah, as you said earlier, we could, we
• 1:02:08
  could talk about this for a week, but we
• 1:02:10
  can't. Um, but uh, I
• 1:02:13
  do uh, want to direct people to your paper if
• 1:02:16
  uh, people are interested in reading your
• 1:02:18
  paper from 2010. Uh, it's
• 1:02:21
  uh, called Determining Habitability. Which
• 1:02:24
  exo Earths, uh, should we search for for
• 1:02:27
  life? And you can find it on the ARXIV
• 1:02:30
  website, is that right, John?
• 1:02:31
  Jonti Horner: Yeah. So that was published in the
• 1:02:33
  International Journal of Astrobiology in
• 1:02:35
  2010. So the ones who want the kind of
• 1:02:36
  scientific reference, it's International
• 1:02:38
  Journal of Astrobiology, Volume 9, page
• 1:02:41
  273 onwards. But um, if
• 1:02:44
  you find it on NASA rads, it'll give you the
• 1:02:46
  archive link which is the pre print Version,
• 1:02:48
  which basically means it's in my formatting
• 1:02:51
  rather than journal formatting. And this is,
• 1:02:54
  it's actually a, uh, handy aside that I'm
• 1:02:56
  sure, as we mentioned before, the
• 1:02:59
  way that a lot of science
• 1:03:01
  works has led to the creation of the most
• 1:03:04
  profitable, um, um, and
• 1:03:06
  problematic, um, companies in the world,
• 1:03:09
  which are the publishing companies. And so
• 1:03:11
  the way a scientist works is we do all this
• 1:03:13
  work, da da da da da. Hooray, hooray, hooray.
• 1:03:15
  We then write a paper to tell the world about
• 1:03:17
  it. We send that off to a journal who
• 1:03:19
  gets another scientist to volunteer their
• 1:03:21
  time, unpaid for free, to referee it.
• 1:03:24
  Then they're charged, typically the scientist
• 1:03:27
  who's written that paper money to publish
• 1:03:28
  that paper for them and then charge everybody
• 1:03:31
  for the privilege of reading it. So if I want
• 1:03:33
  the journal, if I want to read the journal
• 1:03:35
  versions of my papers. Fortunately,
• 1:03:37
  universities have paid access to a lot of
• 1:03:39
  journals, but I'm fundamentally paying to
• 1:03:41
  read my own work. And this is
• 1:03:45
  not ideal. Big deal. I think partly because
• 1:03:47
  as a scientist, you know, I'm paid by
• 1:03:48
  taxpayers money, people are paying me to do
• 1:03:51
  this work. To me, it is really important that
• 1:03:54
  they know what we're doing, they know what
• 1:03:55
  they're getting for their money. And, um,
• 1:03:57
  part of that is be a science communicator.
• 1:03:59
  And I encourage any scientists or budding
• 1:04:00
  scientists, don't refocus on the science.
• 1:04:03
  Focus on communication as well, because if
• 1:04:04
  you do science but can't communicate it, no
• 1:04:06
  one will know what you've done. But to get
• 1:04:09
  around that, what we do in astronomy and
• 1:04:12
  what many disciplines do, is that, uh, we put
• 1:04:14
  preprints up on a publicly
• 1:04:17
  accessible free place. And it's in astronomy,
• 1:04:19
  it's just accepted that with very rare
• 1:04:21
  exceptions, journals will let you do this. So
• 1:04:24
  when we get our paper and we've written it,
• 1:04:27
  some disciplines in astronomy will put the
• 1:04:29
  paper up on the archive when it's submitted.
• 1:04:31
  Some will wait until it's accepted by the
• 1:04:33
  journal when it's refereed. I've always
• 1:04:35
  waited till acceptance, but occasionally if
• 1:04:37
  you've made a big discovery, you want to stop
• 1:04:38
  somebody scooping you to you, you put it up
• 1:04:40
  at submission. There's a growing effort by
• 1:04:42
  scientists to put it up at submission, to
• 1:04:44
  actively solicit feedback from the community
• 1:04:46
  to improve the work, which is good. But those
• 1:04:48
  papers go upon arXiv.
• 1:04:51
  ArXiv, yeah. Um, be very
• 1:04:53
  careful. There is another platform out
• 1:04:56
  there where the letters in ARXIV are shifted
• 1:04:59
  around, which is where a community of people
• 1:05:01
  who espouse Ideas that are not scientifically
• 1:05:04
  verifiable will put their work, uh, and
• 1:05:07
  publish their own little papers. It's a
• 1:05:08
  different thing. But ARXIV is a
• 1:05:10
  repository of free to view things. So if
• 1:05:13
  you are searching for papers, NASA's ADS
• 1:05:16
  system is wonderful. When you click on a
• 1:05:18
  given paper in there, most of them, but not
• 1:05:21
  all of them will have a line that says
• 1:05:22
  journal version or ADS version. But there'll
• 1:05:25
  also be a line that says preprint. And if you
• 1:05:27
  click on the preprint links, it will take you
• 1:05:28
  to the archive and allow you to read the
• 1:05:31
  paper for free. Just to be aware that that is
• 1:05:33
  a version some of the time before
• 1:05:36
  refereeing, most of the time after
• 1:05:37
  refereeing, but before publishing in edits
• 1:05:40
  effectively. So the link you've got to that
• 1:05:42
  is the pre print version of that paper. The
• 1:05:45
  other caution I give to people is that uh, it
• 1:05:47
  is 16 years old. So all of the areas I talk
• 1:05:49
  about in it have moved on. We've learned
• 1:05:51
  more, um, we can talk a bit more about it
• 1:05:53
  next time as well. But always when you read
• 1:05:56
  things, be conscious of the fact that that
• 1:05:58
  science, uh, is fluid. Science changes, our
• 1:06:00
  knowledge changes. I see just in the news
• 1:06:02
  recently, Jason Isaacs Isaacson,
• 1:06:05
  who's I think the head guy at Nashville at
• 1:06:07
  the minute, who's a wealthy multi billionaire
• 1:06:10
  type guy, um, is arguing that the US is
• 1:06:13
  wanting to strongly build a scientific case
• 1:06:15
  why Pluto should be restored as a planet
• 1:06:17
  because fundamentally we discovered it, so it
• 1:06:19
  should still be a planet. And Clyde Tomball
• 1:06:21
  would be turning in his grave.
• 1:06:24
  That is what it is. But it's, it is
• 1:06:27
  important to keep in mind that science
• 1:06:30
  is fluid, it moves. Whereas once something is
• 1:06:33
  published that's static, you know, it's a
• 1:06:35
  window on our knowledge at a time rather than
• 1:06:38
  necessarily the modern version. If I were
• 1:06:41
  to rewrite that paper now, there'd be
• 1:06:43
  advances of course, absolutely.
• 1:06:46
  Andrew Dunkley: But um, yes, um, I think we're trying to
• 1:06:49
  arrange to put the link on the show notes.
• 1:06:51
  I'll just have to remind Huw you about that.
• 1:06:53
  We might wrap it up there. Jonty. Fascinating
• 1:06:55
  topic and uh, it's one we get a heck of a lot
• 1:06:58
  of questions about. So, um, yeah, hopefully
• 1:07:01
  there's a, uh, bit of information in there to
• 1:07:03
  keep people's minds whirring.
• 1:07:06
  Johnty, thanks very much. We will, uh, see
• 1:07:08
  you again real soon.
• 1:07:09
  Jonti Horner: It's an absolute pleasure. Thank you for
• 1:07:10
  having me.
• 1:07:11
  Andrew Dunkley: Professor John Dee Horner, professor of
• 1:07:13
  Astrophysics at the University of Southern
• 1:07:15
  Queensland, standing in for Fred Watson
• 1:07:17
  Watson. And thanks to Huey in the studio. Uh,
• 1:07:20
  Huw couldn't be with us today. Um, he got,
• 1:07:23
  uh, a bit confused.
• 1:07:24
  Jonti Horner: We.
• 1:07:24
  Andrew Dunkley: We know of one planet where there is life.
• 1:07:27
  Huw thought we meant that he was the only
• 1:07:29
  life form on the planet, so he didn't see any
• 1:07:32
  need to turn up today. And from me, Andrew
• 1:07:34
  Dunkley, thanks for your company. We'll see
• 1:07:36
  you on the next episode of Space Nuts.
• 1:07:38
  Jonti Horner: Bye. Bye. You've been listening to
• 1:07:41
  the Space Nuts podcast,
• 1:07:44
  available at Apple Podcasts, Spotify,
• 1:07:47
  iHeartRadio or your favourite podcast
• 1:07:50
  player. You can also stream on
• 1:07:51
  demand@bytes.com.
• 1:07:53
  Andrew Dunkley: this has been another quality podcast
• 1:07:55
  production from bytes.um.com.