Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Mars Gullies Aren't Made by Water: The Surprising Dry Ice Answer

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Mars Gullies Aren't Made by Water: The Surprising Dry Ice Answer · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 0:00
  Andrew Dunkley: Hello. Thanks for joining us. This is Space
• 0:02
  Nuts. A fresh, crisp episode for you
• 0:05
  to devour, I hope. My name is Andrew Dunkley.
• 0:08
  Uh, your host. Great to have your company.
• 0:10
  Uh, a bit of a water theme in this particular
• 0:13
  episode, or partly.
• 0:16
  There's a question being raised in, uh,
• 0:19
  space science about what causes the
• 0:21
  gullies on Mars. Well, we know that gullies
• 0:24
  are caused by, uh, water flows and rainfall
• 0:27
  on Earth. But, um, that can't be the case on
• 0:30
  Mars. Or can it? They think they've figured
• 0:33
  it out and it's quite a surprising thing.
• 0:36
  Uh, we're also going to look at water on the
• 0:38
  moon, or the lack of which could threaten
• 0:40
  future cities and the search for
• 0:42
  ocean worlds. They think they know how. We'll
• 0:45
  tell you all about it on this episode of
• 0:48
  space nuts.
• 0:49
  Generic: 15 seconds. Guidance is internal.
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  10, 9, ignition
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  sequence.
• 0:55
  Professor Fred Watson: Star space nuts.
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  Generic: 5, 4, 3, 2, 1, 2, 3, 4,
• 0:59
  5, 5, 4, 3, 2', 1.
• 1:01
  Andrew Dunkley: Space nuts.
• 1:02
  Generic: Astronau. But it feels good.
• 1:05
  Andrew Dunkley: To help us with all of that is Professor
• 1:07
  Fred Watson Watson, Astronomer Large,
• 1:09
  sporting his new knee because he
• 1:12
  wanted to be needed.
• 1:17
  Professor Fred Watson: Oh, uh, dear. That's all
• 1:20
  right. Um, that's, uh,
• 1:23
  that's as good as they get today.
• 1:25
  Andrew Dunkley: I think it's, you know, that's. That's dad
• 1:27
  joke. Yeah, that's just beyond
• 1:30
  a dad joke. That's. That's weird.
• 1:34
  Professor Fred Watson: So it was three, three weeks ago yesterday
• 1:37
  that I got my new knee. So progress is
• 1:39
  happening. I am walking pretty well now.
• 1:42
  Um, I have yet to
• 1:45
  have my first drive in the car, but that'll
• 1:47
  be this week, I think. I'm told that I'm
• 1:49
  allowed to do that now. I'm off the
• 1:52
  high, um, intensity medication. Uh,
• 1:55
  and, uh, so far, so good. There was a
• 1:58
  bad week last week when things took a turn
• 2:00
  for the worse, uh, because I had an allergic
• 2:03
  reaction to the dressings that were on the
• 2:05
  knee. That can be
• 2:08
  quite dangerous, it turns out. They didn't
• 2:10
  tell me that until after they'd fixed the
• 2:11
  problem. Um, so, yeah,
• 2:14
  anyway, so it's all good. Everybody's happy
• 2:16
  at the moment.
• 2:17
  Generic: Yeah.
• 2:18
  Andrew Dunkley: Uh, the only downside is you've got the
• 2:20
  hybrid knee, which means every night you've
• 2:22
  got to plug it in to charge it.
• 2:25
  Professor Fred Watson: A bionic knee would be good for that. You
• 2:27
  could perhaps get up to speed a bit faster
• 2:29
  than I do at the moment, but no, it's working
• 2:31
  very well. All credit to the team who did the
• 2:33
  job. Dr. Parker and his friends and
• 2:36
  stuff. Uh, we had a great. We had a great
• 2:38
  time. I.
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  Andrew Dunkley: It reminds me of Something my son told me
• 2:42
  about because he's always online looking for
• 2:44
  the next weirdest thing. And he said, um, the
• 2:46
  Chinese, I think the Chinese have invented,
• 2:49
  uh, an exoskeleton that you can
• 2:52
  wear that will walk for you so you
• 2:55
  don't have to make the effort.
• 2:56
  Professor Fred Watson: Yeah, yeah. And run.
• 2:59
  Andrew Dunkley: Oh my goodness.
• 3:00
  Professor Fred Watson: Yeah, they're good.
• 3:01
  Andrew Dunkley: Isn't technology going in strange places,
• 3:04
  directions?
• 3:05
  Professor Fred Watson: That's right, yes.
• 3:05
  Andrew Dunkley: But that, that I think is going to be great
• 3:08
  for people in the future who are um, uh,
• 3:11
  have paralysis problems or.
• 3:12
  Professor Fred Watson: Yeah. Profoundly disabled. That's right.
• 3:14
  Andrew Dunkley: Sort of thing.
• 3:15
  Professor Fred Watson: Mhm.
• 3:15
  Andrew Dunkley: And probably good for rehabilitation. Who
• 3:18
  knows?
• 3:19
  Professor Fred Watson: Maybe. Yeah, maybe.
• 3:21
  Andrew Dunkley: All right, uh, let's uh, talk about these
• 3:24
  storeys that are in the news at the
• 3:27
  moment. And the um, the
• 3:30
  focus is on Mars in terms of uh,
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  uh, images of Martian Gul. Now a lot of
• 3:35
  things about Mars are so strikingly similar
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  to Earth. The canyons and the, and the
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  ocean beds and all that. The only thing
• 3:43
  lacking is well, you know, a breathable
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  atmosphere, liquid water on the surface,
• 3:48
  weather, uh, etc. Gravity, um.
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  But the question has come up as to what
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  causes the gullies on Mars. Now my first
• 3:56
  thought was well hang on a minute, they were
• 3:57
  already there. I mean they happened billions
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  of years ago and that was when water was
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  liquid on the surface. But they've been
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  changing without water.
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  So what's going on?
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  Professor Fred Watson: Uh, indeed, that is a good
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  question. So um, probably you and I spoke
• 4:17
  about um, gullies on Mars a long
• 4:20
  time ago because there was a time when
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  uh, it was being suggested that
• 4:26
  some of these gullies were due to
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  the fact that on the equator on Mars in the
• 4:32
  Martian summertime you can actually
• 4:35
  get temperatures that are high enough for
• 4:37
  liquid water to exist. And the theory was
• 4:39
  that maybe, you know, there's a permafrost of
• 4:42
  uh, ice that come mid
• 4:45
  summer it melts and you get these water
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  flows down slopes which are uh, what cause
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  the gullies. Gullies I guess they're, you
• 4:53
  know, they're the beginnings of rivers really
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  in a way. They're the sort of
• 4:58
  little gentle impressions
• 5:00
  in a landscape which are made by
• 5:03
  flowing water which always wants to go
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  downhill. Uh, and eventually you carve out a
• 5:08
  river valley. Um, but as you say,
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  uh, some of the early observations, I think
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  with Mars Reconnaissance Orbiter, with Mars
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  Express, um, those two
• 5:17
  venerable orbiting uh, spacecraft, it was
• 5:20
  quickly realised that these things change on
• 5:22
  a seasonal basis. And that was why
• 5:25
  uh, the thinking was that maybe there's uh,
• 5:27
  enough water to do it. However, um,
• 5:30
  it turns out that you get these
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  gullies in regions of Mars where the
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  temperature never gets high enough for liquid
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  water to exist on the surface. In other words
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  the, you know, the higher latitude regions,
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  the regions towards the poles. And so
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  what has happened is that a group of
• 5:48
  scientists actually in uh, one of the
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  Parisian uh universities in France,
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  uh, they've looked at the
• 5:55
  alternatives for water. So ruling out water
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  you uh, can do it uh, because there's that
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  we know what the temperature is, we know what
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  the pressure is, uh, it's just not possible
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  for liquid water to exist uh in
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  some of these regions. But they did actually
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  go even a step further. They
• 6:14
  uh, looked um, uh,
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  from the data from Mars Express and Mars
• 6:20
  Reconnaissance Orbiter, they looked at the
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  spectrum of some of these
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  uh, at melting ice fields where
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  you're looking really near the poles, ah of
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  Mars where some of these gullies are. And
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  they found um, there's
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  no signature for water in uh, other words,
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  water ice is definitely not
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  ah, a player or liquid water is definitely
• 6:45
  not a player, um,
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  in this storey. And so the alternative
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  which we know is present on Mars and
• 6:53
  we know that at least some of Mars's polar
• 6:56
  ice caps are made of this is
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  uh, solid carbon dioxide or
• 7:01
  carbon dioxide generally. We
• 7:04
  on Earth are familiar with solid carbon
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  dioxide as dry ice. Uh, uh,
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  on Mars it does exist.
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  We know there's a frost of dry ice near the
• 7:14
  poles. Uh but because the pressure is
• 7:17
  lower on Mars, um, it's got slightly
• 7:20
  different uh mechanisms of
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  behaviour. Uh so uh, it
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  is possible for dryas, dry ice and
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  Earth just sublimes. It goes straight from a
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  solid to a gas. But I think under
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  certain conditions on Mars it can be a liquid
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  for a short time. So uh,
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  what's the storey? These researchers
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  uh had two theories uh which
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  were to try and explain the origin
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  uh of the gullies. Uh
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  one is something which is um, a
• 7:54
  geyser, um, mechanism. The idea is
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  you've got geysers which we're familiar with
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  as jets of hot water uh, coming
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  up from uh, underneath the surface of
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  Earth being heated by magmatic heat.
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  I think both of us, you and I, Andrew, have
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  been to the place that gives those things
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  their name. Geysir in Iceland
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  did visit the guys there.
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  Andrew Dunkley: Oh yeah, yeah, yeah. Actually the best one
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  I've ever seen was in New Zealand.
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  Professor Fred Watson: Yeah, at Rotorua.
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  Andrew Dunkley: Wow.
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  Professor Fred Watson: Rotorua, that's right, yeah. Uh, so
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  anyway, um, we don't call them Rotoruas, we
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  call them geysers. That's because of the one
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  In Iceland. So what's the theory there?
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  The theory is that
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  um, you've got basically
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  a sheet of, of dry
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  ice of solid carbon dioxide that
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  forms in the wintertime.
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  And as spring comes,
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  the heat passing through that sheet of
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  dry ice, uh, basically warms up the
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  soil underneath and that
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  turns some of the ice, this
• 9:05
  carbon dioxide ice, into gaseous carbon
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  dioxide. So you've got a buildup of pressure
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  underneath the sheet of ice and eventually
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  the ice basically ruptures bang and out
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  comes this high velocity jet of carbon
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  dioxide. Um, and the theory
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  is that that takes a lot of soil and
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  uh, you know, dust and stuff with it and that
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  gives you, gives rise to the gullies. It
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  gives you the, basically the
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  discoloration that we see in the gullies.
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  Uh, and that is a mechanism that
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  they looked at. But uh, what
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  has caused them to discard that idea
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  is that the
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  geyser action would appear
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  um, around the spring
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  equinox on Mars. Ah,
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  but you don't see this
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  gully activity, these darkenings of the
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  gullies until later in
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  the year. You don't see them until
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  getting on almost for the Martian summer when
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  those geysers should have shut down. So
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  they ruled that out as the
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  origin. Um, and this
• 10:20
  is the uh, start of what they looked at
• 10:23
  instead, which is something
• 10:26
  a bit similar. But rather than an
• 10:29
  sort of explosive process with the carbon
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  dioxide sort of, you know, bursting out from
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  underneath these sheets of dry ice, uh, what
• 10:37
  you've got is the idea that there are, there
• 10:40
  are small, um,
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  there aren't, you know, there might be small
• 10:46
  cracks in the ice but there's nothing big.
• 10:49
  But what happens instead of the gas
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  bursting out through a large
• 10:54
  crack in the ice, the gas stays underneath
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  the sheet of ice but kind of lubricates
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  it, uh, uh, so that you've got
• 11:03
  essentially a floating sheet
• 11:06
  of dry ice and of course gravity takes over
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  so it slides down the slope and actually
• 11:11
  can cause the appearance of these
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  gullies. Uh, and so uh,
• 11:17
  that's their current favourite theory for
• 11:19
  how these gullies uh, form. And their
• 11:22
  modelling shows that in the end what you've
• 11:25
  got uh, is exactly what we see in uh the
• 11:28
  gullies on Mars. Uh, and they make a comment
• 11:32
  um, that Earth, uh, like features don't
• 11:34
  always require Earth like physics. I think
• 11:36
  that might actually be a comment from
• 11:38
  Universe Today, uh, which is where this
• 11:40
  article comes from.
• 11:41
  An old friend of ours, Univers, uh,
• 11:44
  uh, uh, with Fraser Cain and others,
• 11:46
  uh, um, involved with that. So no liquid
• 11:49
  water on Mars. But uh, dry ice gullies
• 11:52
  perhaps?
• 11:53
  Andrew Dunkley: Yeah. I like the way they
• 11:56
  describe it for people like me to get
• 11:59
  into our heads what might be going on.
• 12:01
  They call it the air hockey effect.
• 12:03
  Professor Fred Watson: Yes.
• 12:03
  Generic: Ah.
• 12:03
  Andrew Dunkley: If anyone's ever been to an arcade and played
• 12:06
  air hockey, it's um, it's played on a
• 12:08
  table with lots of little pinholes in it
• 12:11
  blowing air up, uh, which causes a
• 12:14
  disc to be able to hover when you hit it. And
• 12:17
  that's, that's what they think might be the
• 12:19
  effect that's changing and causing the
• 12:21
  gullies on Mars. So really fascinating,
• 12:25
  really fascinating. Um, the other effect
• 12:27
  is um, is comparing a human bodily
• 12:30
  function. It's not as big and powerful as a
• 12:33
  trumpet, but it could be a silent but deadly.
• 12:40
  Professor Fred Watson: I'm going to leave that one completely alone,
• 12:42
  Andrew.
• 12:43
  Andrew Dunkley: Just leave that one hanging in the
• 12:44
  Professor Fred Watson: air Fred Watson, as you would, yes.
• 12:47
  I'm afraid we've got a dog that does that.
• 12:49
  You don't see that side of Jordy's
• 12:51
  personality. Um, but we do.
• 12:54
  Andrew Dunkley: Hearing, hearing him's enough.
• 12:56
  Professor Fred Watson: Yes it is. Yeah, yeah. Oh, uh,
• 12:59
  gosh.
• 12:59
  Andrew Dunkley: But uh, no, it's fascinating and if you want
• 13:02
  to read about IT, universetoday, uh.com is
• 13:05
  the website where you'll find that very
• 13:07
  interesting storey. This is Space Nuts with
• 13:10
  Andrew Dunkley and Professor Fred Watson
• 13:12
  Watson.
• 13:15
  Generic: 0G and I feel fine.
• 13:17
  Andrew Dunkley: Space Nuts, our uh, next storey takes us from
• 13:20
  not water on Mars to a particular
• 13:23
  lack of water on the moon. And the reason
• 13:26
  they're saying that is because of
• 13:29
  um, you know, the potential for people living
• 13:32
  long term on the lunar surface.
• 13:34
  And up until now they've thought well there's
• 13:36
  a ready supply of water, everything will be
• 13:38
  fine, we can build a million person
• 13:41
  city there and um, yeah, it'll be
• 13:44
  great. Uh, now they don't think that's the
• 13:47
  case. They don't think there's nearly enough
• 13:49
  water to sustain uh, even a small
• 13:51
  city on uh, on the moon. So
• 13:54
  what's um, what's going on there,
• 13:56
  Fred Watson? And there's Earth.
• 13:59
  Professor Fred Watson: Yeah, Earth just making a comment there. Um,
• 14:02
  so thank you Jordan. Yeah,
• 14:06
  uh, very tiring. Yeah. One day
• 14:09
  we'll, I hope he'll end up on the moon.
• 14:13
  So yes, that we've got. And look the
• 14:15
  whole, it's really interesting the extent to
• 14:18
  which our explanation, you know, our
• 14:20
  exploration of the moon in terms of human
• 14:23
  landing is focused on this idea
• 14:26
  of there being copious water uh, on the
• 14:29
  moon. Uh, I'm doing a talk this weekend
• 14:32
  uh, at Macquarie uh, University. I'm their
• 14:34
  Keynote speaker for their open astronomy
• 14:36
  night, which I'm very honoured to be doing.
• 14:39
  Um, and it's. My talk's about the future
• 14:42
  of Artemis and uh, other ventures
• 14:45
  to the Moon. And it all focuses
• 14:48
  on the southern polar region of the Moon
• 14:51
  where
• 14:53
  uh, there is a cluster
• 14:56
  of quite deep craters which
• 14:59
  never see sunlight, uh, because they're
• 15:02
  at the south pole. Um, the
• 15:05
  sun always misses their depths. Uh,
• 15:08
  some of them are quite deep. The one
• 15:11
  actually at the south pole, which is called
• 15:13
  Shackleton Crater, that's four kilometres
• 15:15
  deep, it's 20 kilometres across. Um,
• 15:17
  and uh, the evidence from previous space
• 15:20
  missions is that there is water ice
• 15:23
  in the base of these craters that may be
• 15:25
  billions of years old. Andrew because, uh,
• 15:27
  it's never seen the sun, so it's never been,
• 15:30
  you know, warmed up enough to turn into a
• 15:33
  gas. And the temperature in some of these
• 15:35
  craters is extremely low, um, minus
• 15:37
  200 or thereabouts. So it's frozen
• 15:40
  solid. So, um, we've got this whole
• 15:43
  focus now on getting um,
• 15:46
  spacecraft and humans eventually with
• 15:49
  Artemis 4, hopefully, uh,
• 15:52
  early in 2028, uh, actually
• 15:55
  landing on the Moon in this region. Uh, and
• 15:58
  it's quite a hazardous thing to do because
• 16:00
  the south pole of the Moon is very
• 16:02
  mountainous. It's got all these craters. It's
• 16:04
  not smooth, uh, sailing in terms of
• 16:07
  finding nice, um, flat places to land,
• 16:10
  as happened with the Apollo missions, which
• 16:12
  were all in much less
• 16:15
  challenging parts of the Moon's surf. So the
• 16:18
  focus on water on the Moon is
• 16:21
  enormous and uh, I don't
• 16:23
  know that it's really been
• 16:26
  looked at in great detail before,
• 16:29
  but we now have some work that
• 16:32
  suggests that, uh, yes, there probably
• 16:35
  is water on the Moon's surface,
• 16:38
  but, uh, there might not
• 16:41
  be enough of it to make it,
• 16:44
  um, you know, uh, available on an industrial
• 16:47
  scale, if I can put that. A place where
• 16:49
  humans could survive, uh, permanently or
• 16:52
  where you could have permanent presence.
• 16:55
  So it's um, a theory
• 16:58
  that really I think will start, uh, you know,
• 17:01
  raising a few eyebrows.
• 17:04
  Um, uh, it's come from,
• 17:08
  I guess, um, the idea of
• 17:11
  uh, just how much water there
• 17:14
  is there, um, you know, on the basis of the
• 17:17
  geography, if I can put it that way, the fact
• 17:19
  that you have got these deep craters, um,
• 17:22
  I, I uh, think the
• 17:25
  jury is still out on, on
• 17:28
  um, uh, just how much
• 17:30
  water there is, what form it takes, because
• 17:33
  it, you know, it could be buried under,
• 17:36
  under rock.
• 17:37
  Uh, we're really in a, in a region
• 17:40
  of um, very big unansw
• 17:43
  and um, I don't think we've Talked about
• 17:46
  this, uh, Andrew, but um, Chang'
• 17:49
  E7 which is a Chinese ah, mission
• 17:51
  to land, uh, very near Shackleton Crater,
• 17:54
  actually the one I've just mentioned, uh,
• 17:57
  which was supposed to launch,
• 17:59
  actually I think the day before my knee
• 18:02
  operation it was supposed to launch but it
• 18:03
  was cancelled at very short notice
• 18:06
  with a fairly brief note from the China
• 18:09
  uh, space Agency, uh,
• 18:12
  and uh, that now looks as though it won't
• 18:15
  happen till 2027. But that spacecraft
• 18:18
  carried uh, not just a rover, there's an
• 18:21
  orbiter, a rover and a lander of course, but
• 18:24
  also a hopper, a little
• 18:26
  vehicle that will hop into
• 18:29
  craters rather than try and go down
• 18:32
  into craters on wheels. And
• 18:35
  that's um, the idea is to use that hopper,
• 18:38
  uh, to try and find the water chang' uh e7
• 18:41
  when it is launched, might be the first we
• 18:43
  know of, uh, you know, first, first hand,
• 18:46
  um, experience, if I can put it that way, of
• 18:49
  what the water is like in these craters.
• 18:51
  Sadly uh, we're going to have to wait a bit
• 18:53
  longer than we thought we did. But uh, that's
• 18:56
  one step forward.
• 18:57
  And the hopper by the way is unlike anything
• 19:00
  that NASA is planning for the Artemis
• 19:02
  mission. So really interesting area.
• 19:05
  Uh, we, I think we're still groping in the
• 19:08
  dark a bit, if I can put it that way, given
• 19:10
  that these craters are definitely in the dark
• 19:13
  about just how much water there is. But it's
• 19:15
  possible that there might not be enough to
• 19:16
  make it that uh, well worthwhile.
• 19:19
  Andrew Dunkley: Yeah, I suppose you've got to consider the
• 19:21
  limitations in our capacity to look for it.
• 19:24
  At the moment they've only got the
• 19:26
  ability to look to shallow depths.
• 19:29
  So there could be water uh, deeper in
• 19:32
  the Moon's, um. Yes,
• 19:35
  yes, that, that we haven't found. So
• 19:38
  there may be more.
• 19:41
  But based on what we know now,
• 19:43
  putting a um, a city on the
• 19:46
  moon for you know, hundreds of
• 19:49
  thousands of people, it's just not feasible.
• 19:51
  It wouldn't uh, it wouldn't last. I think
• 19:53
  they said it wouldn't last a year.
• 19:55
  Professor Fred Watson: Yeah.
• 19:55
  Andrew Dunkley: Based on the resources that exist on current
• 19:58
  estimates, I couldn't
• 20:01
  imagine that many people living on the Moon,
• 20:04
  can you?
• 20:05
  Professor Fred Watson: No, not really. Uh, I think um,
• 20:08
  it's not a place you'd want to.
• 20:11
  I can imagine there being things like the
• 20:14
  outpost we have in Antarctica. I think that's
• 20:17
  a sort of reasonably sustainable model for
• 20:20
  exploring the Moon. But yeah, cities of
• 20:24
  tens of thousands of people I think is a non
• 20:26
  starter and this perhaps
• 20:29
  underlines that. That's, I guess the point
• 20:31
  uh, of
• 20:31
  Andrew Dunkley: the article, uh, they do
• 20:34
  go on to say that, um, a village of a
• 20:37
  thousand, maybe ten thousand people would
• 20:39
  last centuries though, if they kept
• 20:42
  the numbers down. So, um,
• 20:45
  the resources that exist at the moment are
• 20:47
  feasible to an extent.
• 20:49
  Professor Fred Watson: Yes.
• 20:51
  Andrew Dunkley: Um, and you
• 20:54
  also have to bring into play things
• 20:57
  like recycling, uh, of water. Uh, they
• 20:59
  use recycled water on the International Space
• 21:02
  Station and I think it's got over 98
• 21:04
  efficiency. You'd have to do that on the
• 21:07
  moon, otherwise you're going to go through it
• 21:09
  like a packet of salt and
• 21:12
  quite.
• 21:14
  Professor Fred Watson: And.
• 21:15
  Andrew Dunkley: And then you've got a real problem. The only
• 21:17
  other way of dealing with it, well, two ways
• 21:20
  would be to transport water from Earth. But
• 21:22
  do we really want to do that? Uh, or harvest
• 21:25
  it. Harvest it from somewhere else.
• 21:28
  Professor Fred Watson: That's the whole point of going to the moon.
• 21:31
  Uh, and of course, this water is not just for
• 21:33
  keeping a city running, it's to act as rocket
• 21:36
  fuel for future, uh, exploration beyond the
• 21:39
  moon. So that's one of the appealing features
• 21:42
  about it. Yeah, very interesting. Um,
• 21:44
  and, uh, it does
• 21:48
  beg the question as to whether strategies
• 21:51
  will change dramatically, uh, once
• 21:54
  we've had a chance to see it firsthand just
• 21:56
  how much water there is there. Because
• 21:59
  that's still.
• 22:00
  Andrew Dunkley: Yeah, it might force Elon to, uh, he's
• 22:03
  abandoned Mars already. Too hard.
• 22:06
  Um, now that the moon's lacking water, he
• 22:08
  might go, well, we won't go there either.
• 22:11
  What's Enceladus doing at the moment?
• 22:15
  Professor Fred Watson: Yes, that's right.
• 22:16
  Andrew Dunkley: Yeah.
• 22:17
  Professor Fred Watson: Could be squirting water out.
• 22:18
  Andrew Dunkley: Yeah, well, that'd make it easy to
• 22:21
  collect. Uh, if you want to read about that,
• 22:23
  it's on the Phys P h y s fizz.org website.
• 22:26
  Or you can read the study that was published
• 22:28
  in Frontiers in Space Technologies.
• 22:32
  You're, uh, listening to Space Nuts with
• 22:33
  Andrew Dunkley and Professor Fred Watson
• 22:35
  Watson.
• 22:38
  Generic: I think we need to do a little more all
• 22:40
  weather testing.
• 22:42
  Professor Fred Watson: Amen, Space Nuts.
• 22:44
  Andrew Dunkley: Our final storey. Fred Watson, uh, continues
• 22:46
  to look for water, but on a
• 22:49
  much larger scale. Uh, we've been looking
• 22:52
  for exoplanets for yonks now
• 22:55
  and we've found five and a half thousand
• 22:58
  plus. But we haven't found a water world,
• 23:01
  an ocean world. And they think they
• 23:04
  now know how to look for them, I
• 23:07
  think is the gist of this storey.
• 23:08
  Professor Fred Watson: That's correct. That's right.
• 23:11
  Um, yeah. So, yeah, this
• 23:14
  is actually a storey I like a lot because I,
• 23:16
  um, remember being very excited,
• 23:19
  uh, back in the early 2000s,
• 23:22
  I guess, uh, when this.
• 23:24
  Exactly this same technique, uh, that is
• 23:27
  being discussed here was used
• 23:30
  to demonstrate that
• 23:33
  uh, Saturn's moon Titan has
• 23:36
  liquid ocean, not liquid oceans, I beg your
• 23:39
  pardon, liquid seas and lakes near its north
• 23:41
  pole. Uh, and it was uh,
• 23:44
  images made by the Cassini spacecraft
• 23:47
  in its early period of uh, orbiting
• 23:50
  around Saturn. The problem with Titan
• 23:53
  is it's got a thick atmosphere, uh,
• 23:56
  that is almost completely opaque. And
• 23:59
  so uh, you can use infrared to penetrate
• 24:02
  through it for a while, but uh,
• 24:06
  to some depth of clarity.
• 24:08
  But um,
• 24:12
  the real way of exploring uh, Titan, which
• 24:15
  is what Cassini did, is by radar,
• 24:18
  uh, you do it by radar. And that's
• 24:21
  uh, one of the reasons that we've been able
• 24:23
  to map uh, these seas and lakes.
• 24:26
  But the way they were first detected was
• 24:29
  when Cassini, uh, when its
• 24:32
  cameras were aimed at Titan,
• 24:35
  Uh, uh, at a time when
• 24:39
  the angle between the
• 24:41
  spacecraft, the moon,
• 24:44
  Titan itself and the sun
• 24:47
  was such that you would get a direct
• 24:49
  reflection off the liquid
• 24:52
  surface that was thought to be near the north
• 24:54
  pole of Titan. And sure enough,
• 24:57
  uh, there was uh, what we call a glint,
• 25:00
  uh, which is a sun glint comes from a
• 25:03
  liquid water surface that was detected.
• 25:06
  That's how Cassini, Cassini first established
• 25:08
  that there are lakes and seas, uh,
• 25:11
  uh, on Titan. And it was then they were
• 25:14
  subsequently mapped uh, very accurately
• 25:17
  by uh, Cassini's radar. I've still
• 25:20
  got some extraordinary maps that came from
• 25:22
  that era showing uh, these seas and
• 25:25
  lakes um, near Titan's north pole. So
• 25:28
  the question that is being asked in this
• 25:30
  piece of research that we're talking about
• 25:32
  once again this comes to us courtesy of
• 25:33
  Universe today, uh, is
• 25:36
  can you do the same thing with
• 25:39
  exoplanets? Supposing you
• 25:42
  have uh, a suspicion that uh,
• 25:45
  One of the 5,500
• 25:48
  now known exoplanets, planets orbiting
• 25:51
  uh, other stars, if you have a suspicion that
• 25:54
  one of them might have conditions where
• 25:56
  liquid water could exist, or in the case
• 25:59
  of, as in the case of Titan, liquid
• 26:01
  hydrocarbons, liquid natural gas.
• 26:04
  Um, could you use this glint technique
• 26:07
  uh, to try and establish if you
• 26:10
  did have a ah, water world, in other words
• 26:14
  a world covered completely by oceans.
• 26:17
  Uh, and those things have been hypothesised,
• 26:20
  actually we've talked about them before,
• 26:21
  these so called Hycean worlds. Uh,
• 26:24
  Hycean is basically a
• 26:27
  term that's been uh, concocted to represent
• 26:29
  a world with an atmosphere of hydrogen.
• 26:31
  That's where the high comes from. Uh, but a
• 26:34
  liquid ocean surface, uh, hence the shen.
• 26:37
  So it's a Haitian world. How could you use
• 26:40
  this glint technique to demonstrate
• 26:43
  that a suspected Haitian world really
• 26:46
  was a Haitian world? So two
• 26:48
  scientists at the University of
• 26:51
  Arizona, uh, which is in Tucson, Uh, I've got
• 26:54
  some good friends there, but they don't
• 26:56
  include these people. I don't know them well
• 26:58
  or all I know is their names. Uh, what
• 27:01
  they've done is they've, they've
• 27:03
  done what you might call the physics of how
• 27:06
  glints might work. Uh, and
• 27:12
  the bottom line is that
• 27:15
  it's potentially a good
• 27:18
  way of doing this. But there are certain
• 27:21
  conditions that have to be
• 27:23
  fulfilled, um, because
• 27:26
  you've got to get the angles right first of
• 27:29
  all. Um, and, and that
• 27:31
  angle is all about
• 27:35
  the object being relatively near to
• 27:38
  its parent star. So you get this
• 27:41
  um, sort of grazing angle almost
• 27:44
  of the water, sorry, the light hitting the
• 27:46
  water and then being reflected back. Now that
• 27:49
  itself presents a problem because,
• 27:51
  um, at the moment most
• 27:54
  of the exoplanets that have been discovered
• 27:57
  uh, are ah, only known because they
• 28:00
  uh, have an effect on their parent star.
• 28:02
  Whether it's blocking the light of the parent
• 28:04
  star as they pass in front of it or whether
• 28:06
  it's pulling it slightly out of position by
• 28:09
  what we call the Doppler wobble, um,
• 28:11
  technique. Uh, these mean that you
• 28:14
  never see the planet that you're trying to
• 28:15
  observe. You just see its effect on the star.
• 28:18
  So really what we're talking about here could
• 28:20
  only apply if you've got direct
• 28:22
  observations of the planet. And if you
• 28:25
  need the planet to be close to the star to
• 28:27
  get the angle right, then that's a chance
• 28:30
  because the star is um, sometimes billions of
• 28:33
  times brighter than the planet that you're
• 28:34
  looking for. However, it's not impossible.
• 28:37
  And there are things called coronagraphs,
• 28:39
  which are essentially uh, devices that
• 28:42
  suppress the light of a star so that you can
• 28:44
  look for planets uh, nearby. And
• 28:47
  so, uh, what um, these
• 28:49
  scientists are doing is feeding this
• 28:52
  information into people who are working
• 28:56
  on uh, something that I think is still a, ah,
• 28:58
  hypothetical spacecraft, uh, something
• 29:01
  called the Habitable Worlds Observatory,
• 29:04
  uh, which will look at the possibility of
• 29:07
  there being habitable worlds among some of
• 29:09
  these, uh, five and a half thousand
• 29:12
  known exoplanets. Uh, what they've done is
• 29:14
  they've fed uh, these conditions,
• 29:17
  this information into the designers to
• 29:20
  say, yeah, you can probably do this, but you
• 29:22
  need to do this, this, this and this when you
• 29:24
  build your spacecraft in order for uh,
• 29:27
  potential water worlds to be discovered. So
• 29:29
  quite a nice piece of research.
• 29:31
  Andrew Dunkley: Yes, indeed. I hope they do find something
• 29:33
  like that eventually. I think it'd be really
• 29:36
  exciting to find a water world,
• 29:38
  ah, ice moons, I suppose count
• 29:41
  because, um, they have
• 29:45
  oceans inside them, but, um.
• 29:48
  Professor Fred Watson: Correct.
• 29:49
  Andrew Dunkley: An actual planet that is
• 29:52
  covered in water. Um, we know of
• 29:55
  only one. But
• 29:58
  there's got to be more, surely. There's got
• 30:01
  to be more. Statistically,
• 30:04
  there's got to be more.
• 30:06
  Professor Fred Watson: Yeah, one would think that's right. Whether
• 30:08
  they are findable by our current technology
• 30:11
  is of course, another question.
• 30:13
  Andrew Dunkley: Yeah, well, um, in time, maybe.
• 30:16
  But then the Vera Rubin Observatory,
• 30:19
  who knows, um, that
• 30:22
  we'd never even thought of.
• 30:24
  Professor Fred Watson: That's correct. And of course an anti Grace
• 30:26
  Roman, uh, spacecraft recently launched,
• 30:29
  which we hope we'll see results from early
• 30:30
  next year, that does have a coronagraph. Uh,
• 30:33
  so it does have a device to look at some of
• 30:36
  these planets directly.
• 30:38
  Andrew Dunkley: Yes, indeed. Uh, very exciting times ahead
• 30:42
  and, um, won't be long before we start
• 30:44
  getting, um, some information back from,
• 30:47
  uh, that telescope either. Uh, it's on its
• 30:50
  way. Uh, yes. Uh, so if you'd like to read
• 30:52
  about that particular storey in the search
• 30:54
  for water Worlds UniverseToday, uh, dot com
• 30:57
  again is, uh, is a source that's, uh, very
• 31:00
  well worth visiting.
• 31:02
  And that brings us to the end of the show.
• 31:05
  Fred Watson, thank you so much.
• 31:07
  Professor Fred Watson: You're welcome, Andrew. Um, it's been a
• 31:10
  pleasure and a privilege to talk to you and
• 31:11
  I. I do hope we can do it again sometime.
• 31:13
  Andrew Dunkley: I, I hope we can do it really, really,
• 31:16
  really, really soon.
• 31:19
  Professor Fred Watson: Maybe so.
• 31:20
  Andrew Dunkley: Catch you soon, professor, uh, Fred Watson
• 31:22
  Watson, astronomer at large. And while you're
• 31:24
  waiting for a new episode, um, please visit
• 31:27
  our website. Uh, you can send us a message as
• 31:29
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• 31:32
  of messages um, from our live audience this
• 31:34
  morning. Hello to Al in Old South
• 31:37
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• 31:39
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• 31:41
  Halil. I hope I got that right. Who's been,
• 31:44
  uh, inspired to, um,
• 31:47
  venture, uh, out with his studies in computer
• 31:50
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• 31:52
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• 31:54
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• 31:59
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• 32:02
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• 32:04
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• 32:06
  shop while you're there. Some new books in
• 32:07
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• 32:09
  Yeah. Uh, and plenty of other things
• 32:12
  to do. And thanks to Huw in the studio.
• 32:15
  Couldn't, um, be with us today. Uh, we were
• 32:18
  talking about sun glints. Well, uh, Huw did a
• 32:20
  bit of a flashing of his own, so I've got to
• 32:22
  go down and bail him out after this. And from
• 32:24
  me, Andrew Dunkley thanks for your company.
• 32:26
  We'll catch you on the next episode of Space
• 32:28
  Nuts. Bye bye, Space Nuts. You've been
• 32:31
  listening to the Space Podcast,
• 32:35
  available at Apple Podcasts, Spotify,
• 32:38
  iHeartRadio or your favourite podcast
• 32:40
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• 32:41
  You can also stream on demand at bytes.
• 32:43
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• 32:46
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• 32:48
  Generic: Com. Um.