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How One Dinosaur-Killing Impact May Have Triggered Global Firestorms · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Andrew Dunkley: Hello again and thank you for joining us on
0:02
another episode of Space Nuts. My name is
0:04
Andrew Dunkley, your host. It's great to have
0:06
your company. I hope you're well and I hope
0:08
you can stick around. We've got some really
0:10
great storeys today. These are fascinating.
0:13
Remember that asteroid impact that led to the
0:16
loss of the dinosaurs, you know, happened a
0:18
couple of weeks ago? Uh, well, uh, it
0:21
may have been much worse than we first
0:23
thought. Lost lots of, uh, crispy critters as
0:26
a consequence. We'll explain all that. Uh,
0:28
there was a near Earth asteroid discovered
0:31
around 30 years ago. 30 years ago. Well, now
0:34
new evidence suggests it may
0:37
have been a comet. And I love
0:40
this storey. This is about a Canadian amateur
0:43
astronomer who was planning a trip online
0:45
using, uh, using online maps. And
0:48
he made a massive discovery. We'll tell you
0:51
all about it on this episode of space nuts.
0:54
Generic: 15 seconds. Guidance is internal.
0:56
10, 9. Ignition
0:59
sequence start.
1:00
Jonti Horner: Space nuts.
1:01
Generic: 5, 4, 2, 1, 2, 3, 4,
1:04
Jonti Horner: 5, 5, 4, 3, 2, 1. Space
1:07
nuts.
1:07
Generic: Astronauts report it feels good.
1:10
Andrew Dunkley: And joining us, uh, this time around
1:12
with Fred Watson, gallivanting around chasing
1:15
solar eclipses is Professor Jonty
1:18
Horner, professor of Astrophysics at the
1:20
University of Southern Queensland. Welcome
1:21
back, Jonty.
1:22
Jonti Horner: Oh, uh, thanks for having me. It's good to be
1:24
the substitute Yorkshireman again.
1:26
Andrew Dunkley: Yes, we've got a whole set of them.
1:30
It's really good stuff.
1:31
Um, now we've got some amazing
1:34
storeys. I know you've been a very busy young
1:37
fellow for, um. Well, since we last
1:40
spoke to you, uh, you do your own sort of
1:42
gallivanting, but we managed to nail you down
1:45
for a couple of weeks, which is fantastic.
1:48
Uh, let's get straight into it because, um,
1:51
these storeys dovetail. Well, we've got an
1:53
asteroid that
1:56
may have been a comet. Then we've got an
1:58
asteroid that hit Earth that seems, uh, to
2:00
have done more damage than we thought. And
2:02
then we've got a hole in the ground
2:04
discovered while someone was planning a
2:06
holiday. All kind of related.
2:08
So let's get stuck into the, uh, first
2:10
storey. A near Earth asteroid that
2:13
was discovered 30 years ago they think might
2:16
have been a comet.
2:18
Jonti Horner: Yeah, this is a lovely storey and it ties
2:21
into something that we've talked about in
2:23
different lights previously when I've been on
2:26
the show, and I'm sure Fred Watson spoken
2:27
about it quite frequently as well, which is
2:29
that, uh, very human need to break things up
2:32
into manageable chunks, you know, so you
2:35
go from being a child to being a teenager to
2:37
being an adult and there's A miraculous day
2:38
when you wake up and you're suddenly legally
2:40
able to drive.
2:41
Andrew Dunkley: Yes.
2:41
Jonti Horner: And in different countries, that's a
2:43
different debt. But we all have it. But
2:45
fundamentally, you're not really any
2:47
different as a person the day before that and
2:49
the day after it. What we're doing is we're
2:51
breaking up this kind of continuum of human
2:53
experience into chunks, where we group things
2:56
that are similar together and we put things
2:58
that are more different into separate groups.
3:00
And I've talked about this in the past when
3:02
we've talked about the difference between
3:04
planets and stars and that amazing middle
3:07
ground that are brown dwarfs, where in
3:09
effect, you've actually got objects of all
3:12
sizes from the size of a grain of sand,
3:14
actually from the size of a single atom or a
3:16
single subatomic particle, all the way up to
3:18
the biggest galaxies and beyond in this kind
3:21
of continuum of sizes. But you go through
3:24
kind of rock to planet to brown dwarf to
3:26
star. And we put these arbitrary divisions in
3:29
so that we can group things that look similar
3:31
together and study them to make life easier.
3:35
And we talked about that, of course, in the
3:37
context of Pluto, with the whole thing of
3:39
when is a planet not a planet, when it's a
3:41
dwarf planet, and why all that happened.
3:43
That's exactly the same kind of thing. In my
3:45
kind of contextualization, that was the right
3:46
decision. That's a hill I'll quite happily
3:48
plant my flag on. But
3:51
Pluto's like the gangly teenager. From a
3:53
distance, it looks big and like a serious
3:54
adult, but it's still not very good at
3:56
tidying its room up. That's the kind of
3:57
analogy you there. This
4:00
whole storey is another one of those same
4:02
things. If we had been talking
4:05
300 years ago, people would have been
4:08
familiar with comets, at least the bright
4:09
ones. You know, things that get bright enough
4:11
to see with the naked eye that have a glowy
4:13
coma and a tail. They appear briefly, then
4:15
vanish forever. And we had great comets a
4:18
couple of times in the last few years, on
4:20
average one per decade. But it's a bit hit
4:22
and miss. And the idea is, with modern
4:24
scientific knowledge, what you're seeing when
4:27
you get that phenomenon is a big dirty
4:29
snowball or a snowy dirt ball that's whizzing
4:31
around the sun on this hugely elongated
4:33
orbit. When it's far from the sun and it's
4:36
nice and cold, we just don't see it. You'd
4:38
need the biggest telescopes on the world
4:39
because you've just got this little thing
4:41
reflecting a bit of sunlight. But when it
4:44
comes near to the sun, its surface gets hot.
4:47
The volatile material on it gets too hot to
4:50
still be solid, so turns into gas. And
4:53
that gas erupts from the surface, carrying
4:55
with it dust, shrouds that snowball
4:58
in what's called a coma, a big spherical
5:00
cloud of gas. And then the solar wind pushes
5:03
the gas and dust away from the sun and you
5:04
get the tails. And so a comet, as we see
5:07
it, is pretty big, can be millions or
5:10
tens of kilometres, tens of millions of
5:12
kilometres across, which is this huge amount
5:15
of gas and dust floating around in the solar
5:17
system, all given off by an icy,
5:19
rocky, rubbly object only a few kilometres
5:22
across in the head. And that's a comet. So
5:25
it's basically something that has activity
5:27
that out gases as it goes around the sun.
5:29
Andrew Dunkley: Yep.
5:31
Jonti Horner: 19. In 1801, sorry came along
5:34
and Giuseppe Piazzi found Ceres, which
5:37
was an object between the orbits of Mars and
5:39
Jupiter. And he found it because they were
5:41
looking for a planet, because people had
5:43
suggested that might just be that there's a
5:46
planet between Mars and Jupiter. So the
5:47
celestial police were looking, but Piazzi got
5:50
there first and that was the first of the
5:51
asteroids. And over the decades, and
5:54
the couple of centuries that followed, one
5:56
object became four, became tens,
5:59
became hundreds, became thousands, and
6:02
nowadays it's over a million. And if we
6:04
were talking kind of 30 or 40 years ago, we'd
6:07
have had a very clear idea of what an
6:09
asteroid is and that an asteroid is very
6:12
different to a comet. So an asteroid is a
6:14
rocky or metallic object that
6:17
even when it gets near the sun, just stays as
6:19
a rocky metallic object. No gas comes off it,
6:21
just a lump of rock or rubble going around
6:23
the sun. So
6:26
rocky, rubbly object, icy object with loads
6:28
of gas. You've got a comet, you've got an
6:30
asteroid, very distinct.
6:33
Now, water's got a bit more muddied for
6:36
a few reasons over the last few decades.
6:38
Firstly, you had objects called the
6:41
Centaurs, which I studied for my PhD, that
6:44
are big icy objects that are too far away
6:46
from the sun most of the time to outgas. So
6:49
got kind of asteroidal classifications and a
6:51
couple of them got a bit nearer in and
6:53
started out gassing, so got a dual classific.
6:57
Chiron is the most famous. Chiron has both an
6:59
asteroidal classification and, um, a cometary
7:01
classification. Cause sometimes it looks like
7:03
an asteroid, sometimes it looks like a comet.
7:06
You then have things like the Geminid meteor
7:08
shower every December, which is our best
7:10
meteor shower. I love it dearly. Almost
7:13
all of the meteor showers are produced by
7:15
comets and we get them when we go through the
7:17
dust that has been left behind by the
7:18
activity of the comet when it was out
7:20
gassing. But when they found the parent of
7:22
the Geminids, it doesn't look like a comet,
7:25
it's an asteroid. So the idea became that
7:28
maybe it's a rock comet and it's getting so
7:29
close to the sun it's shedding dust and we
7:32
get the meteor shower. Then there were
7:35
a couple of comets that were lost. And then
7:38
many, many decades later, an asteroid was
7:40
found that looked to be moving on the same
7:42
orbit as a comet. And so maybe they're the
7:44
same object and the comet has turned off. And
7:47
when the comet has turned off and stopped
7:48
making any gas, maybe it looks like an
7:51
asteroid. So there's this blurring going on.
7:55
In reality, what you've got is a
7:57
continuum from rocky and metallic and nothing
8:00
else on one end to incredibly icy on the
8:02
other, and everything in between where you
8:04
have more rock, less ice, more ice, less rock
8:07
blurring together. That's a
8:10
hell of a lengthy introduction, hell of a lot
8:12
of background to give the context for this
8:14
storey. So, in light of all that, back in
8:17
1998 there was this near Earth
8:20
asteroid discovered. It goes by the of 1998
8:23
SH2 and it looks like a lump of rock.
8:25
It goes around the sun every four or five
8:27
years, whizzing around. It's been seen at a
8:30
few apparitions since. And, um, that's all
8:33
well and good. We know a few thousand Near
8:35
Earth asteroids now and we're finding more
8:37
and more of them all the time. And people are
8:39
particularly interested because, of course,
8:40
if they come near the Earth, there's a
8:42
possibility that eventually one of them will
8:44
come too near the Earth and will hit us and
8:46
we'll have issues. And ask the dinosaurs
8:49
about that. We can come back to that a little
8:50
bit later on. So there's a lot of interest in
8:53
learning more about near Earth asteroids and
8:56
following them because the longer you observe
8:57
them, the more accurately you know how
8:59
they're moving. So the better you can predict
9:01
into the future where they'll be and
9:04
therefore rule out the chance of that object
9:06
hitting the Earth. Uh, may also, of course,
9:09
be interesting to people who want to mine
9:10
that object in the future with off Earth
9:12
mining that if you want to go mine it, you
9:14
need to know where it is. Yeah, so
9:17
that's this object. Brilliant. We found an
9:20
Earth asteroid.
9:21
Where it gets interesting for this storey
9:24
is that, uh, back in August 2025,
9:27
which is what, 27 years after this thing was
9:29
discovered it had another close approach
9:32
to Earth. Now, this wasn't like the
9:35
forthcoming approach for the asteroid
9:37
Apophis, which is going to come closer to us
9:39
than geostationary satellites. This was close
9:42
to astronomers and distant to everybody else.
9:44
You're talking about the thing coming about 3
9:46
million kilometres away at its closest
9:48
approach. Now, that's relatively close, but
9:51
it's not something to get particularly
9:53
panicked about. That's nearly 10 times as far
9:55
away as the moon is, about 8 times as far
9:57
away as the Moon is. But it's near enough
10:00
that if you want to learn more about the
10:01
asteroid, what you can do is you can get the
10:03
planetary radar, uh, that they used to beam
10:06
radar, uh, out into space and bounce it off
10:08
things and get it back. Yeah, to try and
10:10
bounce radar, uh, off this asteroid
10:13
to get an image of what its shape is, to
10:15
learn about its rotation and figure out how
10:17
big it is. Because even with the biggest
10:20
telescopes on the planet, something like this
10:23
is always just a single pixel. You can't zoom
10:26
in. So what they did was they got the
10:28
planetary radar, uh, sent radar out to this
10:31
object and missed
10:34
a little bit. Embarrassing as you do, it
10:37
wasn't quite where it was supposed to be.
10:40
So based on all those historical
10:41
observations, you can predict into the future
10:44
where the asteroid will be based purely on
10:47
the gravity of all the planets. It's getting
10:49
pulled around by the Earth, uh, and Venus,
10:51
Jupiter, everything's pulling and tugging on
10:53
it. And you can in a very prescriptive way
10:56
run its orbit forward in time and say where
10:57
it will be in the future if the only thing
11:00
acting on it is gravity.
11:03
But it wasn't where it should be. Uh, the
11:06
fact it wasn't where it should be says
11:08
something else is happening as well.
11:10
Something else is happening to push it around
11:12
now. So at this point, sometimes that we get
11:14
the, oh, well, it must be an alien spaceship
11:17
thing happening. That's exactly what's
11:19
happened in the past with people suggesting
11:21
there's maybe something more going on that
11:24
actually hasn't happened with this one, which
11:26
is really nice to see. But what
11:28
that being out of position tells you is that
11:31
there are non gravitational forces acting on
11:33
this thing. Something other than gravity is
11:36
happening to push it around a little bit.
11:39
Now, M. If we rewind to comets for a little
11:41
bit. I remember when I was a teenager back in
11:43
the early 1990s, we had Comet Swift Tuttle
11:46
came past and, um, Comet Swift Tuttle's a
11:48
parent of the Perseid shower. And, um, that
11:51
was kind of a relief because at, uh, Its
11:52
previous apparition, Comet Swift Tuttle, had
11:54
been seen widely observed and had been
11:57
predicted that it would come back in about
11:59
120 years. It would come back in the early
12:01
1980s and it didn't show up.
12:04
M which was a bit weird because this is a
12:06
bigger and more active comet than Comet
12:08
Hallie. It's probably the biggest of the
12:10
comets with a period less than 200 years.
12:12
Pretty epic object. And it came back 10
12:15
years later. Now, by the time it came back,
12:17
people had figured out kind of what was going
12:18
on, had realised that it was going to be
12:21
late. But part of the complexity there
12:24
was that, uh, because this is quite an active
12:25
comet, when it's ejecting gas and dust to
12:28
space, that process acts like a
12:31
rocket engine that pushes it around. So it's
12:33
ejecting gas in one direction and that exerts
12:36
a force pushing the nucleus in another.
12:38
And that is not a predictable thing in
12:41
that every time a comet comes around the sun,
12:44
its rotation will be a bit different. Some
12:46
active areas will turn off and some will turn
12:48
on. So while you can get a general trend and
12:51
you can make loose predictions, there's
12:53
always going to be a bit of uncertainty in
12:55
where a comet will be in the future because
12:57
it's got these forces pushing and nudging it
12:59
around. You know, it's a bit like, I don't
13:02
know if you could strap a few fireworks to a
13:04
snowball and throw it up in the air. That's
13:05
probably not very healthy to do. But you get
13:07
the same kind of thing, they go off at
13:08
different times and be pushed around all over
13:11
the place. Um, interestingly, Comet Encke,
13:13
which is a comet with the shortest non
13:15
orbital period, has been seen every three and
13:18
a half years, 3.3 years for more than 200
13:20
years. And we've actually seen its orbital
13:22
period get shorter and then get longer again
13:24
as a direct result of the jets on its
13:26
surface, uh, pushing it around and those jets
13:29
changing the rotation direction of the
13:32
comet. Loads of cool stuff there.
13:36
So with that knowledge, you can look at this
13:39
object, 1998 SH2.
13:41
It's not where it's supposed to be. So that
13:44
suggests that there's non gravitational
13:45
forces happening. But whenever people have
13:48
observed it in the past, it has looked inert.
13:50
Uh, it's looked like an asteroid.
13:53
What that suggests is that it is active.
13:56
It's got some outgassing happening, but at
13:58
such low levels that it wasn't possible to
14:01
detect them before. So that was a clue
14:04
that seems a really likely storey.
14:06
So scientists go away and they do a couple of
14:08
things. Firstly, they look for pre discovery
14:11
observations of this, you know, times when
14:13
there was a photographic plate made 50 years
14:16
ago that just happened to have the object in
14:17
the field of view so you can get a longer
14:20
period of knowledge of how it's moved.
14:22
Andrew Dunkley: Yeah.
14:23
Jonti Horner: And um, with these really accurate
14:25
observations, you can tell that it has been
14:27
misbehaving for a long time. It's getting
14:29
pushed and nudged around. What then
14:32
happened was they used some of the really
14:34
biggest telescopes in the world to take a
14:36
look at it and detect just a tiny hint of gas
14:39
being emitted, tiny little wisp.
14:42
And so you put all that together and um, this
14:44
thing is probably, of all the comets we know
14:46
in the solar system, the least active that we
14:49
currently know of. But it is exhibiting
14:51
cometary behaviour. So it's another object
14:54
really straddling the boundary. And it's
14:56
fascinating. It'll be wonderful to learn more
14:58
about it. But it's fascinating too,
15:02
because here's the thing that looks like an
15:04
asteroid, sounds like an asteroid. It does
15:06
everything you'd expect an asteroid to do,
15:08
except it's wibbling and misbehaving a bit.
15:10
Now, if you're finding hundreds and thousands
15:13
of near Earth asteroids and you want to know
15:14
whether the Earth's safe, well, if you see
15:17
something that's an asteroid, you can predict
15:19
where it is with gravity going forward, the
15:22
Earth's safe. What this is telling you is
15:24
that, uh, gravity may not be enough. So you
15:27
can't just say, well, it looks like it'll be
15:28
safe, we'll stop looking. Because if this
15:31
object's unpredictable, what about all the
15:33
other ones we're finding too?
15:34
Andrew Dunkley: I was about to bring that up. There's got to
15:36
be more than one.
15:38
Jonti Horner: Oh, absolutely. Um, we found
15:41
quite a few of these over the years now in
15:43
various circumstances. My favourite
15:46
really is the Taurid stream of debris. We get
15:48
the Taurid meteor shower every year from
15:50
about September to December. We've got the
15:52
northern and southern Taurids. We also get a
15:54
daytime meteor shower in June called the Beta
15:57
Taurids. Result is we spend about
15:59
four months of every 12 passing
16:02
through this enormous broad swath of debris
16:05
where on any given night, when the meteor
16:07
shower is active even at its peak ulcely,
16:09
four or five meteors an hour, the debris is
16:12
very spread out. But because the Earth spends
16:14
so long going through it, we get more debris
16:16
from that stream than all other meteor
16:18
showers combined over the course of a year.
16:22
At the core of that is Comet Encke, which is
16:25
that comet with a 3.3 year period, but
16:27
also a huge amount of other rubble and
16:30
debris. There's lots and lots of asteroids or
16:33
things that behave like asteroids moving
16:35
around in the storage stream. And the idea is
16:37
that this was a, uh, mega comet 20 or
16:40
30,000 years ago that fell apart,
16:43
giving us this stream of debris. Comet Encke
16:46
was probably behaving like an asteroid if
16:48
he'd found it a thousand years ago. But
16:50
something happened 250 years ago to wake it
16:53
up and it started behaving like a comet and
16:55
we see it as a comet. And the other asteroids
16:58
in that stream are currently dormant and
17:01
there's a load of them. So it's likely in the
17:03
inner solar system that even just in the
17:06
Taurid Stream, you're going to have hundreds,
17:08
if not thousands of objects just like
17:10
1998 SH2 that straddle
17:13
that boundary between the comet and the
17:15
asteroid.
17:18
Andrew Dunkley: Fair enough. And, uh, as a consequence of
17:20
that, they've had to rename it.
17:23
Jonti Horner: Yep. So it now has a cometary classification
17:26
as well. What happens with comets is you
17:29
get. When people find a comet,
17:32
um, it's C, slash, then the year,
17:35
ah, and then a catalogue number. So basically
17:37
every comet gets a unique identifier. So we
17:39
remember Chuchinshan Atlas, which,
17:42
um. I'm trying to remember the correct ID for
17:45
it, but it was, I think it was like 2023
17:47
A, ah, 1 or something like that, A3. So
17:50
the A means that it's discovered in the first
17:52
fortnight of the year. 3 is the third object
17:54
found in the first fortnight of the year.
17:56
That tells you about the comet and then
17:59
it's named after the discoverer in brackets.
18:02
If the comet is seen at more than one
18:04
apparition, the C gets changed to a P to show
18:06
that it's periodic. In this
18:09
case, because this already has
18:12
an asteroidal name by which
18:15
it's known, it's kept that, but they've added
18:17
a P in front of it. So it's gone from being
18:19
1998 SH2 to being
18:22
P. 1998 SH2,
18:25
um, will be interesting to see whether down
18:28
the line they add the name of the discovery
18:29
facility to it. Um, that wouldn't surprise
18:32
me. That's been done for previous occasions
18:34
where we've had an asteroid that became a
18:36
comet. But it'll be interesting to see. But
18:38
it's. I guess what I love about this is
18:41
you get into the nitty gritty of it, but it's
18:43
that reminder of the beautiful complexity
18:45
we've got. There's so much more to learn.
18:48
Andrew Dunkley: Absolutely, yes. Uh, it's a really good
18:50
storey and, um, one worth reading up. You can
18:53
do that@space.com or you can
18:55
read the published findings in the journal
18:58
Nature Astronomy. This is Space Nuts with
19:01
Andrew Dunkley and Professor John T Horner.
19:06
Jonti Horner: The crew of Artemis 2 now bound for the moon.
19:09
Generic: Humanity's next great voyage begins.
19:12
Jonti Horner: Space note Nuts.
19:13
Andrew Dunkley: Let's move from a comet flying through
19:16
space to a comet, uh, or an asteroid in this
19:19
case, that stopped, uh, flying through space
19:22
because a big planet called Earth got in the
19:24
way. And the one
19:27
that, um, is referred to as, uh,
19:30
or creating the Chicxulub crater
19:33
in what is now known, uh, as the Gulf of
19:35
Mexico. Uh, and we even know the
19:38
exact impact point because they've been down
19:40
there and taken samples, uh, which was a very
19:43
exciting storey when we covered that sometime
19:45
back. But now they've taken another look at
19:47
this, uh, and gone back to the very moment of
19:50
impact and the few hours afterwards and
19:53
decided by the look of it that this thing was
19:56
much more brutal than
19:59
we first envisaged.
20:02
Jonti Horner: Absolutely. And this kind of ties in with the
20:04
storeys that were told again. Back when I was
20:06
a teenager, I remember hearing about the
20:10
impact that killed the dinosaurs and storeys
20:12
about what would have happened on the other
20:14
side of the planet and the idea of firestorms
20:17
and, you know, it was a hellish experience
20:18
worldwide. But the way you'd normally hear
20:21
this storey relatively recently is you had
20:23
the impact. Things were bad in the vicinity
20:26
of the impact. Shockwaves went out, tsunamis
20:28
went out. So over a very large area, it was
20:30
immediately fairly devastating. But
20:33
there was a huge amount of dust and debris
20:35
flung into the Earth's atmosphere, which led
20:38
to this prolonged nuclear winter type event.
20:40
You know, it blocked the sun, got really
20:42
cold, the plants died, the animals died. Then
20:45
when the clouds cleared, it got really,
20:47
really nasty because you got this period of
20:49
runaway global warming and hideous acid rain
20:51
because the impact had hit rocks that were
20:53
packed with carbon and sulphur
20:56
carbonate and sulphate rocks, which led to,
20:58
uh, carbonic and sulfuric acid
21:01
rain. It led to an atmosphere super loaded
21:04
with greenhouse gases. So it basically
21:06
made the planet fairly hellish for a few tens
21:09
of thousands of years, from one stage to the
21:11
next to the next. But when I was
21:14
younger, there were these storeys about while
21:16
there were probably global firestorms. The
21:18
idea that an impact halfway around the world
21:21
could set fire to forests elsewhere.
21:24
And in recent years I've not heard
21:27
that storey told so much. It's kind of fallen
21:29
a little bit out of fashion. But the new
21:31
research that's been done here is kind of
21:34
bringing that idea back into the picture.
21:37
Now, the idea here is that you get this
21:40
impactor that was probably about 10
21:41
kilometres across, smacking into the Yukon
21:44
Peninsula, creating a crater that was
21:47
two to 300 kilometres in diameter.
21:50
In doing that, it would have flung a huge
21:51
amount of rocky material, vaporised material,
21:55
out of the atmosphere. And a lot of that
21:57
material would have travelled at speeds
21:59
slower than the Earth's escape velocity to
22:01
rain back down into the atmosphere. And when
22:03
that material falls back into the atmosphere,
22:05
it's travelling at speeds of kilometres per
22:07
second, so it ablates like a
22:10
fireball that we see in the sky, like a
22:11
meteor. But you're not seeing one or two,
22:13
you're seeing a huge deluge of material
22:15
raining down all across the planet.
22:18
Now, when these bits of material hit
22:21
the atmosphere and ablate, what they're doing
22:23
is they're taking the kinetic energy of their
22:25
Martian and emitting, turning it into heat
22:28
and light, which, you know, if you get a
22:30
single small meteor, you're not gonna get
22:32
sunburn from it. If you get something the
22:35
size of the Chelyabinsk impact, people
22:36
actually did get sunburn, um, from that, from
22:38
the brightness of the flash. Now imagine,
22:41
instead of having one Chelyabinsk impact,
22:43
having this rain of material falling into the
22:45
atmosphere all across the planet, creating
22:48
this, what's described as a thermal pulse
22:51
that has been discussed and
22:54
previous models, things that have come out,
22:56
suggested that that effect would have been
22:58
like putting a grill on. It would have been
23:01
really quite unpleasant for thin skinned
23:03
animals that were exposed to it. You'd have
23:04
got burned, you might even have got killed.
23:07
But if you were, uh, underground or you were
23:09
underwater, you'd have been able to live
23:12
through it. I mean, you'd have lived to see
23:14
all the other horrors that were coming from
23:16
the impacts. It wasn't really a good news,
23:17
Storey, but you'd have probably survived it.
23:20
But the argument had been that that thermal
23:22
pulse from that material coming into the
23:24
atmosphere would not have got things hot
23:26
enough to ignite things like grasses. You
23:29
know, the tinder that you get that can start
23:32
forest fires and things like this, which I
23:34
think is why that idea of the global
23:36
firestorms had gone away. What
23:39
the new research has done is looking at
23:41
fossil sites in North America, which must be
23:43
remembered, was quite close to the impact,
23:46
relatively speaking, on a global sense. They
23:48
found this layer of spherules of material,
23:51
which is a debris that rained back down to
23:53
Earth, uh, in the fossil record and above it
23:56
there's this very thin layer of silicate
23:59
dust which must have fallen out at about the
24:01
same time. Now the
24:04
idea is that that silicate dust
24:07
would have effectively acted like a bit of a
24:09
doona with that raining down and that in the
24:11
atmosphere. The fact that it's fallen in the
24:14
fossil record above the spherules
24:17
means the spherules got to the ground before
24:19
the dust got to the ground, effectively. So
24:22
the researchers have said, well, what would
24:24
happen if you had all this dust, all this
24:25
silicate dust in the atmosphere and you had
24:28
these ferrules running through, giving off
24:30
all this heat? And it's effectively like that
24:33
dust in the atmosphere would have acted a bit
24:36
like a reflecting, uh, blanket or something
24:38
like that. It would have trapped even more of
24:40
the heat in the atmosphere and reflected it
24:42
back down at the ground. And, um, the
24:44
calculations that they've made suggest that
24:47
that extra energy, because of the energy
24:49
being re radiated back down to the ground,
24:51
rather than escaping to space, would have
24:54
made things hot enough for grass to catch
24:56
fire, for pine cones to catch fire. Not
24:58
enough not for an entire tree to burst into
25:01
flames, but for all the tinder that was lying
25:03
on the ground to be called a flame.
25:06
And if that happens, what you do is you
25:08
trigger global firestorms. So you
25:11
turn a situation and you make it much, much
25:13
worse. Now, what should be said
25:16
here is this, uh, work is looking at North
25:19
America and it strikes me that further
25:22
away from the impact site, you probably
25:23
wouldn't have got the impact dust. So it
25:25
might well be that you actually had a
25:26
gradiated kind of level of nastiness from the
25:29
impact. So nearby it brutal. And
25:32
then you had the tsunamis and stuff washing
25:33
out on the far side of the planet. You
25:36
probably didn't get the silicate dust, so you
25:38
just got the normal level of hellishness
25:40
where you didn't set off firestorms, but
25:42
things were nasty. But there was probably
25:44
this sweet spot like the ultimately bad
25:47
porridge in the Cinderella Storey, where
25:49
things were ultimately worse, ultimately
25:52
as bad as they could be, where the impact
25:55
way over the horizon, way in the distance,
25:58
was enough to trigger forests to burst into
26:00
flame because of igniting the tinder enough
26:02
to cook animals alive as they were on the
26:05
surface. Uh, really kind of brutal and
26:08
remarkably horrific imagery.
26:11
But it's fascinating work and m it's another
26:14
insight into just how bad impacts like this
26:16
could be. It's that whole thing that we're
26:18
playing with a detective storey that is 66
26:21
million years old and we're trying to piece
26:23
together the narrative of what happened and
26:26
every bit of information we get like this
26:27
just seems to make a more and more horrific
26:29
piece picture.
26:30
Andrew Dunkley: Yeah, I mean, the original consensus was
26:33
the, um, asteroid hit
26:36
the planet and, uh, it
26:39
created, um, tsunamis that went around the
26:41
world, um, three, four times, something like
26:43
that. Um, and uh, created
26:47
the equivalent of a nuclear winter and
26:49
everything died and there was no food and,
26:52
uh, the creatures died along with it over a
26:55
period of time. But this is suggesting that a
26:58
lot of, um, the initial death,
27:01
uh, due to these firestorms happened in a few
27:03
mere hours. Um, it's a
27:06
horrifying thought.
27:08
Jonti Horner: It is. And I mean, you start getting to that
27:10
kind of philosophical side of thing is does
27:12
this make it better or does it make it worse?
27:14
You know, if you were there at the time,
27:15
would you rather be broiled and baked and
27:17
cooked quickly or left to starve slowly in
27:20
the cold that followed it? Yeah, I mean it's
27:23
all fairly bleak, but it is also that
27:25
reminder drawing just a bit like we were
27:27
talking about in the previous storey. We are
27:28
in the crosshairs. This will happen again.
27:30
It's not like the Earth has been hit for the
27:32
last time unless we do something about
27:35
it. And it's great that we have the capacity
27:38
to discover objects further and further
27:40
from the Earth with a greater and greater
27:42
lead time before they come close to us. It's
27:44
great that we're learning the capacity to
27:46
deflect them. But it's sometimes hard to
27:49
justify to people why people are doing this
27:51
kind of research. And it's one of the
27:53
arguments we have, for example, against the
27:55
satellite megalithic constellations, because
27:57
we're finally a spec that can look out at the
27:59
cosmos and detect threats. And what we're
28:02
doing is we're throwing tinsel in the way and
28:04
hiding the view.
28:06
Andrew Dunkley: And that is a bit of a worry. Well, it's a
28:08
big worry and it's not getting any better. In
28:10
fact, it's going to get worse. We'll um,
28:13
probably discuss that more in our next
28:15
episode.
28:15
But, um, I did notice
28:18
in sort of looking at this storey that, uh,
28:21
some papers or some websites refer to
28:24
it as a meteorite impact rather than an
28:26
asteroid. Why would they do that?
28:28
Jonti Horner: This is interesting with terminology and
28:31
I'm less uncomfortable with the idea of
28:34
meteorite impact, asteroid impact being
28:37
a conflation. The terminology of
28:39
objects is a weird one and
28:42
astronomers have very specific terminology
28:46
that then gets a little bit confused when you
28:48
see popular science and you see the news and
28:50
all the rest of it when something's floating
28:53
around in space nowhere near the Earth,
28:56
we refer to it as a meteoroid
28:59
or an asteroid or comet, basically.
29:02
Um, and we talked about asteroids and comets
29:04
earlier on and where the line blurs there.
29:07
The typical boundary between
29:09
calling a meteoroid and an asteroid is
29:12
often taken as being about one metre in size,
29:15
but that's just fairly arbitrary.
29:18
When something enters the atmosphere and it's
29:21
pushing the air in front of it and it's
29:22
glowing in the sky, that phenomenon we call
29:25
a meteor, if it's really bright, we call it
29:28
a fireball. And that boundary is set roughly
29:30
as bright as a planet Venus. If we see an
29:32
explosion at the end, we call it a bolide.
29:34
And that just means exploding fireball,
29:36
basically. So meteor, bolide,
29:39
fireball are uh, atmospheric phenomena.
29:42
You're not actually seeing the thing coming
29:43
through the atmosphere, you're seeing the gas
29:46
that it's heated up and excited in the
29:48
atmosphere. That's what you're seeing as a
29:50
glow. When it reaches the ground and hits the
29:53
ground, you call it a meteorite. That's the
29:55
physical object on the ground or hitting the
29:58
ground. Now, whether
30:01
you call something like this a meteorite
30:04
impact or an asteroid impact, I think it's
30:05
probably both. You know, technically the
30:08
asteroid hits the ground, um, you
30:11
could call it a meteorite. But maybe what you
30:13
should do is have that idea in your head of
30:15
if it's less than a metre across, you could
30:17
call it a meteorite. Bigger than that, you'd
30:19
call it an asteroid. I've never seen
30:21
clarification on where that
30:24
boundary comes because terms are used in
30:26
different sensors kind of thing. So for me,
30:29
I don't think it's unreasonable to say
30:31
meteorite impact here, although you're
30:32
probably pushing the size definition.
30:36
Call it an asteroid or comet impact is
30:38
probably more reasonable. And it might be
30:40
that if you dug into the physics of it and
30:42
you were to do an IAU resolution a bit like
30:44
we did with Pluto, maybe what you do is look
30:47
at it in terms of the effect of the
30:49
atmosphere on the object coming in. So
30:52
things that create fireballs and bolides in
30:54
day to day life, the atmosphere is much
30:57
bigger in size than the object coming in,
31:00
which means wind resistance will eventually
31:02
slow it down. So the meteorite that we talked
31:05
about a few months ago that landed on
31:06
someone's driveway in Canada was travelling
31:09
at about the same speed that a rock dropped
31:11
out of an aircraft would have done. It was at
31:12
terminal velocity. Its speed was
31:15
governed by the atmosphere. Whereas with
31:18
things that are kilometre scale, the
31:20
Atmosphere is essentially not there. It's not
31:22
going to slow them down. And so I wonder
31:25
whether there is an argument that you could
31:26
set up a definition that said if it's
31:29
travelling at uh, speed less than
31:31
supersonic, you'd call it a meteorite impact.
31:34
If it's travelling faster than that, maybe
31:36
you'd call it an asteroid impact. But I don't
31:38
think that there's any official delineation
31:40
like that. That's just kind of how I think
31:43
about things in my own head.
31:44
Andrew Dunkley: No, I like that that works. Well, well,
31:46
that's probably a good way to think about it.
31:49
Um, another interesting storey that uh, the
31:52
asteroid impact uh, that killed the dinosaurs
31:55
was a lot more damaging in the early stages
31:57
than we first thought by the look of. But uh,
32:00
plenty of, plenty of websites and news
32:02
platforms have picked this one up, not
32:04
surprisingly. Uh, but you can read
32:07
at uh, the Science
32:10
Advances, uh, website published in
32:13
Science Advances. Uh, this is Space Nuts
32:15
Andrew Dunkley here with Johnty Horner.
32:20
Jonti Horner: 0G and I feel fine.
32:22
Andrew Dunkley: Space Nuts, the storey. Jonty
32:25
takes us to Canadia and
32:27
this is a storey, uh, about a
32:30
Canadian amateur astronomer who
32:33
decided to plan a holiday using online maps.
32:36
It is.
32:36
Jonti Horner: This is lovely. I think we've all done this
32:38
to some degree. You planning your holiday,
32:41
planning your road trip. I just had a lovely
32:42
holiday with the in laws. And you look at uh,
32:45
the online maps of your choice that typically
32:47
have really nice satellite images of the
32:49
places you're um, and you try and figure out
32:52
what you're going to see, what you're going
32:53
to go there. And to some degree you sat
32:55
browsing around thinking, I wonder if I can
32:57
see anything unusual, what's it like around
32:59
there? And that's what happened
33:02
here. We've got this amateur astronomer going
33:05
by the name of Joel Lapointe who back in
33:08
2024 was planning his hiking and
33:10
camping trip. And I think it's in northern
33:13
Quebec. It's near a place called Lake Mars.
33:17
And he found this unusual looking
33:20
feature next to that lake. Looks a bit odd
33:23
on the maps on the satellite imaging. Now
33:26
there is a university in Canada that has a
33:29
website called Impact Earth that allows
33:31
people to, as a kind of popular
33:34
um, collaborative endeavour for
33:36
citizen science is the word I'm looking for
33:39
to log things where people think they've
33:42
found impact features. So being an
33:45
amateur astronomer being aware of this, he
33:46
logged it. I think I found a crater. About
33:49
a year later, um, the site
33:52
as a result of this report was
33:55
explored, visited by a planetary geologist
33:57
from the university called Gordon Ozinski.
34:00
Who went there, took a lot of samples,
34:03
explored around and confirmed that
34:06
this really is an impact feature. It's an
34:07
impact crater about
34:10
390 million years old,
34:12
so way older than the impact that killed the
34:14
dinosaurs. About 25 kilometres
34:17
across, which includes a load of
34:20
incredibly well preserved features in terms
34:23
of glassy hardened volcanic type rocks from
34:26
the impact that he himself has said he's
34:29
surprised at that well preserved, given how
34:30
old it is and how far north this is, how cold
34:33
the weather gets in the winter and stuff. Now
34:36
this makes it the biggest crater found on
34:38
Earth since 2018, when there was a crater
34:40
discovered under the Greenland ice sheet. But
34:43
the difference is that the one under the
34:45
Greenland ice sheet is below a kilometre's
34:47
depth of ice. So it isn't like we can get
34:50
there and learn much more about it. That's
34:51
still quite a mysterious spot.
34:54
Whereas this is open and exposed and
34:56
accessible, so people are able to go there
34:59
and explore it, learn a lot about it. There's
35:02
some really nice imagery out there on the
35:05
Internet about this. From the maps, images
35:07
where it was found to images of
35:10
features called shatter cones, which are the
35:12
kind of thing created that are very typical
35:15
of an impact crater formed under very high
35:17
pressure, very high temperature molten rock.
35:20
So it is absolutely amazing.
35:23
But it's also to me kind of breathtaking that
35:26
here is a feature 25 kilometres in diameter
35:29
in the middle of a built up, well, not that
35:32
built up country, but in the middle of a
35:34
country near a famous lake, there is an
35:37
impact crater that had never been identified
35:39
until now. You know, we're still discovering
35:43
kilometres, tens of kilometre scale features
35:45
on the Earth. I mean, that's just
35:47
astonishing.
35:50
Andrew Dunkley: Uh, yeah, it is. And um, I
35:53
think we've talked about it in the past that
35:56
one of the problems with finding these things
35:58
on Earth is the fact that the Earth's kind
36:00
of covered up with vegetation and uh,
36:03
you know, lots of, um, weather, uh,
36:06
activity which has caused erosion and then
36:08
we've got earthquakes that have caused
36:10
mountain ranges to pop up here and there. And
36:12
so a lot of these impact points get uh,
36:15
disturbed or are hidden. Not uncommon
36:18
now.
36:20
Jonti Horner: Absolutely. And I mean 70% of the Earth's
36:22
surface is water and you need to be a bigger
36:25
impacter than the depth of the ocean to leave
36:27
a scar on the ocean floor. So the
36:30
history of impacts on the Earth is very much
36:32
muddied by all of these different
36:35
processes. The Ice Ages have scoured the
36:37
surface of the Earth clean. We've got
36:39
weathering, we've got forests, the Earth's
36:41
surface is actually an incredibly dynamic
36:43
place compared to the Moon. If you look at
36:46
the Moon, there are many craters of this kind
36:48
of size. And one of the things that is
36:50
actually discussed in the articles online
36:51
about this is whether this could be a venue
36:54
for people to learn more in preparation for
36:56
visits to the Moon where we can go to craters
36:58
or vice versa. Whether we could learn more
37:00
about craters like this by going to the ones
37:02
on the Moon that are the same size but are
37:04
pristine because we're at a similar
37:06
location with similar targets in the shooting
37:08
gallery. But on the Earth everything gets
37:11
worn away fairly effectively, whereas on the
37:13
Moon it stays pretty pristine until something
37:16
else hits it and weathers it away. The only
37:18
real way you're going to weather lunar
37:19
craters, um, with a few exceptions, is
37:22
by other things hitting them and muddying the
37:24
water. There is going to be a lot more to
37:27
learn about this. It is still relatively new
37:30
news. The geologists involved
37:33
won't be going there year round because it
37:35
gets really, really cold and really
37:36
unpleasant in the winter. So there'll be
37:38
summer expeditions going there, trying to
37:40
learn more about it, getting more and more
37:42
samples of it. Because we don't know many
37:44
craters that are that old on the Earth.
37:46
Andrew Dunkley: No, this is 390 million
37:49
years. That's a long time back, isn't
37:51
it? That's over 300 million years beyond the
37:54
dinosaur impact.
37:56
Jonti Horner: Absolutely pretty impressive. It's far from
37:59
the oldest crater on the Earth, but I would
38:01
argue that we know far more younger craters
38:04
than this than. We know older craters than
38:06
this.
38:06
Andrew Dunkley: Yeah. Didn't they recently say they found
38:09
the oldest one in Western Australia? Was it?
38:12
Jonti Horner: Yeah. Then I think that was a little bit
38:15
controversial, but there was a lot of talk
38:16
about shattercons with that one as well.
38:18
Andrew Dunkley: Yes, there was, Yeah, I remember that.
38:21
Jonti Horner: You know, these are, uh, we're finding
38:23
craters more and more and they tell us about
38:25
the history of the Earth and the heritage of
38:27
it. With the really old craters, there's even
38:30
some arguments that the, ah, largest impacts
38:33
that happened very early on in the Earth's
38:35
history were actually the seeds of the
38:38
continents to some degree. There was some
38:40
amazing work. This is probably actually best
38:43
part of a decade ago now. But there was great
38:45
work by Craig o' Neill and his team that were
38:47
looking at trying to model the initiation of
38:50
plate tectonics on the Earth. So how did
38:51
plate tectonics get going? And, um, these
38:53
incredibly talented geophysicists here in
38:55
Australia were running models where
38:58
you start the Earth with no plate tectonics,
39:00
looking at the interior, looking at how hot
39:02
it was back then. And if you started the
39:04
Earth without plate tectonics, plate
39:06
tectonics didn't happen. And uh, what they
39:08
thought could be the smoking gun was that you
39:11
had impacts that caused a big impulse of
39:14
energy and motion in the mantle
39:17
that triggered a downwelling which would then
39:19
trigger an upwelling and you could get impact
39:21
induced plate tectonics which would then
39:24
cause these things to maybe even give you the
39:26
seeds of the continents of the earliest
39:28
continents. And that's an
39:31
awesome storey. The videos that they made of
39:32
their simulations were fabulous. And
39:35
um, yeah, it's amazing what more there is
39:37
still to learn, I guess.
39:38
Andrew Dunkley: Yeah, absolutely true. And this is another
39:41
storey that's been picked up by Orlin Sundry.
39:44
Uh, so, um, yeah, you shouldn't have any
39:46
trouble finding it if you do, um, a search
39:48
for the Canadian amateur astronomer who was
39:51
planning his holiday. And uh, the storey will
39:53
pop up just about everywhere. Space.com, the
39:56
Smithsonian magazine, et cetera, et cetera.
39:58
Uh, and uh, by, by now,
40:01
when you hear this episode or very close to
40:04
this point in time, uh, the team
40:07
that uh, made the discovery will be
40:09
presenting their work at the 88th Annual
40:11
Meeting of the Meteor. Uh,
40:14
meteoritis. I can't say
40:17
it, uh, Meteorocital
40:20
Society in Germany, I think. That's right. I
40:22
don't know. Anyway, yeah, look it up. It's a
40:25
great yarn.
40:25
Uh, we've had a very rocky programme today.
40:29
Um, Jonty, it's been fascinating the
40:32
way those storeys all dovetailed into each
40:34
other. Uh, and we're at the end. Thank you
40:36
very much. Nice to see you again.
40:39
Jonti Horner: Uh, it's good to be back. Thank you for
40:40
having me and hope
40:41
Andrew Dunkley: Fred Watson's enjoying his jaunt
40:44
chasing a, uh, solar eclipse.
40:45
Jonti Horner: Yes, yes, it's a hard life but somebody's got
40:48
to do it.
40:48
Andrew Dunkley: Absolutely true. I'm waiting for one to come
40:50
to me. I only have to wait two more years.
40:52
Jonti Horner: Two more years.
40:54
Andrew Dunkley: Thanks.
40:54
Jonti Horner: And it'll be cloudy. You know it's going to
40:56
be cloudy.
40:56
Andrew Dunkley: Oh yeah, it's probably going to be raining
40:57
training and I'm m giving up a game of golf
41:00
for it too. All right, thanks Jonty. We'll
41:02
see you soon. Yeah, It's a pleasure,
41:05
Professor Jonty Horner, professor of
41:06
Astrophysics at the University of Southern
41:08
Queensland. Don't forget, uh, to visit us
41:11
online while uh, you are, ah, waiting for the
41:13
next episode,
41:14
spacenutspodcast.com
41:17
and have a look around while you're there.
41:18
Visit the shop, etc etc and thanks to Huw in
41:21
the studio couldn't be with us today. Um, put
41:23
his home address in Google Maps. We haven't
41:25
seen him since. And from me, Andrew Dunkley.
41:27
Thanks for your company. We'll see you on the
41:29
next next episode of Space Nuts. Bye. Bye.
41:33
Jonti Horner: You've been listening to the Space Nuts
41:35
podcast, available at
41:38
Apple Podcasts, Spotify,
41:40
iHeartRadio or your favourite podcast
41:43
player. You can also stream on
41:44
demand@bytes.com M.
41:46
Andrew Dunkley: This has been another quality podcast
41:48
production from bytes.com.