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00:00:00 --> 00:00:02 Anna: They went looking for the bottom of a lake.
00:00:02 --> 00:00:05 They found the inside of a volcano
00:00:05 --> 00:00:07 Avery: and then they found that water had been
00:00:07 --> 00:00:08 through it three separate times.
00:00:09 --> 00:00:11 Anna: Perseverance at the Edge of Jezero Crater
00:00:11 --> 00:00:13 published Monday, and it rewrites what that
00:00:13 --> 00:00:15 shoreline actually is.
00:00:15 --> 00:00:18 Avery: Also today, Europe's Jupiter probe comes home
00:00:18 --> 00:00:20 on Monday night and for 15 minutes it flies
00:00:20 --> 00:00:23 straight over Australia in a dark sky.
00:00:23 --> 00:00:25 Anna: Two teams, two completely different
00:00:25 --> 00:00:28 techniques, both pointing at a fifth planet
00:00:28 --> 00:00:30 hiding inside the most famous planetary
00:00:30 --> 00:00:31 system we have ever photograph.
00:00:32 --> 00:00:34 Avery: And water in an interstellar comet and what
00:00:34 --> 00:00:37 its heavy hydrogen says about the star that
00:00:37 --> 00:00:37 made it.
00:00:37 --> 00:00:38 Anna: I'm Anna.
00:00:38 --> 00:00:39 Avery: I'm, um, Avery.
00:00:39 --> 00:00:41 Anna: This is Astronomy AstroDailyPod. And this is
00:00:41 --> 00:00:44 series five, episode 200. In
00:00:44 --> 00:00:47 September of 2023, NASA's perseverance
00:00:47 --> 00:00:49 rover drove up onto a strip of ground called
00:00:49 --> 00:00:52 the Margin Unit. It hugs the inner edge of
00:00:52 --> 00:00:55 Jezero Crater's rim and it runs along what
00:00:55 --> 00:00:57 was once the shoreline of a lake. If you had
00:00:57 --> 00:00:59 asked the science team what they expected to
00:00:59 --> 00:01:01 find there, the answer would have been
00:01:01 --> 00:01:04 straightforward. Sediment, clay and silt
00:01:04 --> 00:01:07 laid down in layers the way sand piles up on
00:01:07 --> 00:01:10 a lakebed over thousands of years. There was
00:01:10 --> 00:01:12 a good reason to expect it. Orbiters had been
00:01:12 --> 00:01:14 picking up strong signals of carbonate murals
00:01:14 --> 00:01:17 from that spot for years. On Earth,
00:01:17 --> 00:01:19 carbonates very often form in shallow lakes
00:01:19 --> 00:01:22 and shallow seas. Exactly the kind of
00:01:22 --> 00:01:25 warm, wet, shallow environment where life can
00:01:25 --> 00:01:28 get a foothold. And exactly the kind of rock
00:01:28 --> 00:01:29 that is good at preserving the evidence
00:01:30 --> 00:01:32 afterwards. That is a large part of why
00:01:32 --> 00:01:34 Jezero was chosen as a landing site in the
00:01:34 --> 00:01:35 first place.
00:01:36 --> 00:01:38 Avery: So they drove up expecting a beach.
00:01:38 --> 00:01:40 Anna: And what the rover found was igneous rock.
00:01:41 --> 00:01:43 Rock that forms from magma either deep
00:01:43 --> 00:01:46 underground or from volcanic activity at the
00:01:46 --> 00:01:48 surface. The work was published on Monday in
00:01:48 --> 00:01:50 the journal Communications Earth and
00:01:50 --> 00:01:53 Environment, published by Candace Bedford, a
00:01:53 --> 00:01:55 research scientist at Purdue University in
00:01:55 --> 00:01:56 Indiana.
00:01:56 --> 00:01:58 It went straight to the Journal. There is no
00:01:58 --> 00:02:00 preprint sitting behind it. So what we are
00:02:00 --> 00:02:03 describing is the peer reviewed version, not
00:02:03 --> 00:02:05 an early draught. The instrument doing the
00:02:05 --> 00:02:08 heavy lifting is Supercam. It sits up on the
00:02:08 --> 00:02:10 rover's mast and it works by firing a laser
00:02:10 --> 00:02:13 at a rock from as far as six and a half
00:02:13 --> 00:02:16 metres away. The laser vaporises a tiny
00:02:16 --> 00:02:18 patch of the surface into a glowing plasma.
00:02:18 --> 00:02:20 And the spectrum of light coming off that
00:02:20 --> 00:02:23 plasma tells you what the rock is made of.
00:02:23 --> 00:02:25 Perseverance has done this on more than
00:02:25 --> 00:02:28 185 bedrock targets across
00:02:28 --> 00:02:31 the Margin unit. And the rover did not just
00:02:31 --> 00:02:33 sample one spot. It worked its way across
00:02:33 --> 00:02:36 about 265 metres of elevation
00:02:37 --> 00:02:39 from high on the unit down to the old
00:02:39 --> 00:02:42 lakebed. That vertical range turns out to be
00:02:42 --> 00:02:42 the whole storey.
00:02:43 --> 00:02:44 Avery: What changes as you go down?
00:02:45 --> 00:02:47 Anna: High up, the rock is coarse, greened and
00:02:47 --> 00:02:50 crystalline, and it's dominated by olivine, a
00:02:50 --> 00:02:52 mineral made of magnesium and iron. Coarse
00:02:52 --> 00:02:55 crystals mean slow cooling. This rock formed
00:02:55 --> 00:02:58 in a body of magma well underground, cooled
00:02:58 --> 00:03:00 slowly enough for its grains to grow large,
00:03:01 --> 00:03:04 and only reached the surface much later after
00:03:04 --> 00:03:06 everything above it had eroded. And up there,
00:03:06 --> 00:03:09 it's almost pristine. Almost no sign
00:03:09 --> 00:03:12 that water ever touched it. And lower down,
00:03:12 --> 00:03:15 lower down on the lake bed itself, the same
00:03:15 --> 00:03:17 rock looks transformed. The olivine grains
00:03:17 --> 00:03:19 are fractured and there's silica sitting
00:03:19 --> 00:03:21 between them. Same starting material,
00:03:21 --> 00:03:23 completely different history.
00:03:23 --> 00:03:25 That's what makes igneous rock so useful
00:03:25 --> 00:03:28 here. And it's slightly counterintuitive. We
00:03:28 --> 00:03:30 tend to think of sedimentary rock as the
00:03:30 --> 00:03:33 record keeper. But mineral crystals in
00:03:33 --> 00:03:35 igneous rock preserve the precise conditions
00:03:35 --> 00:03:37 of the moment they formed. And when water
00:03:37 --> 00:03:39 comes through later and alters them, it
00:03:39 --> 00:03:42 leaves a signature too. So instead of a
00:03:42 --> 00:03:44 beach, the team got something arguably
00:03:44 --> 00:03:47 better. A rock that had been written on more
00:03:47 --> 00:03:49 than once and kept every draught
00:03:50 --> 00:03:53 three separate episodes. Here is the sequence
00:03:53 --> 00:03:55 the team reads out of the chemistry. And I
00:03:55 --> 00:03:58 want to be precise about this because it is
00:03:58 --> 00:04:00 the finding. First, carbon
00:04:00 --> 00:04:03 dioxide, rich groundwater came up through the
00:04:03 --> 00:04:05 rock and reacted with the olivine. That
00:04:05 --> 00:04:08 reaction produced carbonate and it filled the
00:04:08 --> 00:04:10 fractures running through the bedrock at the
00:04:10 --> 00:04:13 low elevations. Today, those carbonate
00:04:13 --> 00:04:16 filled fractures are left standing proud like
00:04:16 --> 00:04:19 ridges, because the softer rock around them
00:04:19 --> 00:04:21 has worn away faster. Second, an
00:04:21 --> 00:04:24 episode that may well be the lake itself.
00:04:24 --> 00:04:27 Turning olivine into carbonate leaves silica
00:04:27 --> 00:04:30 behind. And Eleni Ravanis at the University
00:04:30 --> 00:04:32 of Hawaii at Manoa, a, uh, co author,
00:04:33 --> 00:04:36 puts it that they see more of that silica in
00:04:36 --> 00:04:38 the rocks that sat below the waterline.
00:04:38 --> 00:04:41 And third, in one location, in the eastern
00:04:41 --> 00:04:43 part of the margin unit, there are mineral
00:04:43 --> 00:04:46 veins about 25 centimetres thick, and
00:04:46 --> 00:04:49 they contain calcium sulphate and fluorite.
00:04:50 --> 00:04:53 Fluorite is the tell. On Earth, fluorite
00:04:53 --> 00:04:55 typically forms when hot water circulates
00:04:55 --> 00:04:58 through volcanic rock. That points to a later
00:04:59 --> 00:05:01 heated underground water event, something
00:05:01 --> 00:05:03 quite different from the first two.
00:05:03 --> 00:05:06 Avery: So why does any of this bear on the question
00:05:06 --> 00:05:07 people actually care about?
00:05:07 --> 00:05:10 Anna: When water interacts with olivine on Earth,
00:05:10 --> 00:05:13 the reaction can release hydrogen. Hydrogen
00:05:13 --> 00:05:16 is a food source for certain microbes, and
00:05:16 --> 00:05:19 the same reaction leaves behind carbonate and
00:05:19 --> 00:05:21 silica to two minerals that happened to be
00:05:21 --> 00:05:24 very good at locking in traces of whatever
00:05:24 --> 00:05:27 was living there. So what the Margin unit is
00:05:27 --> 00:05:29 describing is not a single wet moment.
00:05:30 --> 00:05:32 It is a place where the right chemistry was
00:05:32 --> 00:05:35 available repeatedly over a long stretch of
00:05:35 --> 00:05:38 the planet's history. Bedford's own framing
00:05:38 --> 00:05:41 is that this location became, quote, a
00:05:41 --> 00:05:43 sort of crossroads for aqueous systems.
00:05:43 --> 00:05:46 And she makes the point that reaches past
00:05:46 --> 00:05:48 Jezero. This crater sits inside
00:05:48 --> 00:05:51 one of the largest exposures of carbonate
00:05:51 --> 00:05:54 anywhere on Mars. If the carbonate here did
00:05:54 --> 00:05:57 not form the way everyone assumed from orbit,
00:05:57 --> 00:05:59 that is a question mark hanging over a lot of
00:05:59 --> 00:06:01 other carbonate on that planet,
00:06:01 --> 00:06:03 Avery: which is a slightly uncomfortable finding for
00:06:03 --> 00:06:04 orbital geology.
00:06:05 --> 00:06:07 Anna: It is, and Bedford says so almost
00:06:07 --> 00:06:10 cheerfully. Her line is that after 10 years
00:06:10 --> 00:06:12 working with Mars rovers, what she has
00:06:12 --> 00:06:15 learned is that Mars constantly throws
00:06:15 --> 00:06:17 surprises at you and that it's very rare for
00:06:17 --> 00:06:20 things to be as we expect them to be from
00:06:20 --> 00:06:23 orbital data. Now, three things to hold
00:06:23 --> 00:06:26 onto and none of them are optional. One,
00:06:26 --> 00:06:28 the team can establish the order of these
00:06:28 --> 00:06:31 water events. They cannot date them. We know
00:06:31 --> 00:06:34 first, second, third, we do not know
00:06:34 --> 00:06:36 when and we do not know how far apart.
00:06:36 --> 00:06:39 Two, and this is the important one, this is a
00:06:39 --> 00:06:42 habitability result. It is not a detection of
00:06:42 --> 00:06:45 life and it is not a biosignature.
00:06:45 --> 00:06:48 Nobody on this team is claiming one. We are
00:06:48 --> 00:06:50 saying the ingredients and the conditions
00:06:50 --> 00:06:52 were there more than once, which is a
00:06:52 --> 00:06:55 genuinely different statement and a weaker
00:06:55 --> 00:06:58 one. Three, the origin of the margin
00:06:58 --> 00:06:59 unit is still argued over.
00:07:00 --> 00:07:02 Earlier this year, a separate team used the
00:07:02 --> 00:07:05 rover's ground penetrating radar, rimfax,
00:07:05 --> 00:07:08 to look underneath this same ground and
00:07:08 --> 00:07:11 reported layered beds dipping down towards
00:07:11 --> 00:07:13 the basin, the sort of structure you would
00:07:13 --> 00:07:15 associate with a delta front. That's not
00:07:15 --> 00:07:18 obviously the same picture as slowly cooled
00:07:18 --> 00:07:21 magma from deep underground. Both results
00:07:21 --> 00:07:24 are real measurements. Reconciling them is
00:07:24 --> 00:07:26 unfinished business and we'll tell you when
00:07:26 --> 00:07:27 it's finished.
00:07:27 --> 00:07:29 Avery: And, um, is there an Australian connection to
00:07:29 --> 00:07:30 the storey?
00:07:30 --> 00:07:33 Anna: There's no Australian science team on this
00:07:33 --> 00:07:35 paper and we're not going to pretend
00:07:35 --> 00:07:38 otherwise, but there is an Australian link in
00:07:38 --> 00:07:40 the chain and it's a real one. Every bit of
00:07:40 --> 00:07:43 this data came, uh, to Earth through NASA's
00:07:43 --> 00:07:45 Deep Space Network. And one of the network's
00:07:45 --> 00:07:48 three complexes is at Tidbinbilla outside
00:07:48 --> 00:07:50 Canberra. The Canberra Deep Space
00:07:50 --> 00:07:53 Communication Complex, managed for NASA by
00:07:53 --> 00:07:56 the csiro. When Mars is on the
00:07:56 --> 00:07:59 sky over the Southern hemisphere, Canberra is
00:07:59 --> 00:08:02 the ear listening the laser fires on Mars.
00:08:02 --> 00:08:04 The answer comes home through the act.
00:08:04 --> 00:08:07 Supercam itself is co led by Purdue,
00:08:07 --> 00:08:10 Los Alamos National Laboratory and
00:08:10 --> 00:08:12 IRAP and CENS in
00:08:12 --> 00:08:15 Toulouse. It's a genuinely international
00:08:15 --> 00:08:16 instrument.
00:08:16 --> 00:08:19 Avery: Well, here's one for our Australian listeners
00:08:19 --> 00:08:21 to mark in their calendars next Monday night.
00:08:21 --> 00:08:24 If you are anywhere in Australia with a clear
00:08:24 --> 00:08:27 sky, there is a spacecraft passing overhead
00:08:27 --> 00:08:30 that is on its way to Jupiter. The
00:08:30 --> 00:08:32 European Space Agency confirmed the details
00:08:32 --> 00:08:35 on Monday. Juice, the Jupiter
00:08:35 --> 00:08:38 icy moons explorer, returns to Earth on
00:08:38 --> 00:08:40 28 September for its third gravity
00:08:40 --> 00:08:43 assist. Closest approach is over the Indian
00:08:43 --> 00:08:46 Ocean at 11:45 UTC.
00:08:46 --> 00:08:49 The flyby bends the spacecraft's path by
00:08:49 --> 00:08:52 about 20 degrees and adds roughly
00:08:52 --> 00:08:55 3.5 kilometres per second to its
00:08:55 --> 00:08:57 speed. No fuel spent, just
00:08:57 --> 00:09:00 geometry and the Australian part.
00:09:00 --> 00:09:03 Between 15 and 30 minutes before that
00:09:03 --> 00:09:06 closest approach, JUICE crosses Australia,
00:09:06 --> 00:09:08 travelling from the northeast of the country
00:09:08 --> 00:09:10 to the northwest. We ran the clock on that
00:09:10 --> 00:09:13 and it works out beautifully. That crossing
00:09:13 --> 00:09:16 falls between about 9:15 and 9:30
00:09:16 --> 00:09:19 in the evening, Eastern Standard Time, in
00:09:19 --> 00:09:22 Central Time roughly quarter to 9 to 9 o',
00:09:22 --> 00:09:24 clock, and in Western Australia between about
00:09:24 --> 00:09:27 7:15 and 7:30 in the evening.
00:09:28 --> 00:09:30 Now here is why that is worth clearing your
00:09:30 --> 00:09:33 Monday night for. The sun sets in
00:09:33 --> 00:09:35 Brisbane at 10 to 6, in Darwin
00:09:35 --> 00:09:38 at about 20 to 7 and in Perth at a
00:09:38 --> 00:09:41 quarter to 6 with which means that when Juice
00:09:41 --> 00:09:43 comes over, it is properly dark
00:09:43 --> 00:09:44 everywhere.
00:09:44 --> 00:09:47 The entire continent is in night and the
00:09:47 --> 00:09:50 spacecraft is tracking straight across the
00:09:50 --> 00:09:52 top of it. Make it I no,
00:09:52 --> 00:09:55 and let's be honest about that, ESA's own
00:09:55 --> 00:09:58 wording is that amateur astronomers with the
00:09:58 --> 00:10:00 right telescope or binocular equipment may
00:10:00 --> 00:10:03 be able to track it. This is a small
00:10:03 --> 00:10:06 spacecraft, a long way off, moving fast.
00:10:06 --> 00:10:08 It is a target for someone who knows what
00:10:08 --> 00:10:10 they are doing with a scope and a set of
00:10:10 --> 00:10:13 coordinates. Not something you will catch by
00:10:13 --> 00:10:15 looking up. But for that crowd, it is a
00:10:15 --> 00:10:17 genuine opportunity and there will be very
00:10:17 --> 00:10:20 few chances left. Juice only comes back
00:10:20 --> 00:10:23 Once more in January 2029.
00:10:23 --> 00:10:26 Anna: There's one more detail worth having because
00:10:26 --> 00:10:28 it's the part that makes flight controllers
00:10:28 --> 00:10:31 nervous in the way in. Juice passes through
00:10:31 --> 00:10:33 Earth's shadow for about eight and a half
00:10:33 --> 00:10:35 hours, ending in the early hours of Monday
00:10:35 --> 00:10:38 morning, European time. No sunlight at
00:10:38 --> 00:10:38 all.
00:10:39 --> 00:10:41 The spacecraft runs on battery power alone
00:10:42 --> 00:10:43 and then comes out the other side and
00:10:43 --> 00:10:46 performs the most precise manoeuvre of its
00:10:46 --> 00:10:46 year.
00:10:47 --> 00:10:49 Avery: Remind everyone where it's been launched.
00:10:49 --> 00:10:52 Anna: On an Ariane 5 from Kourou in April
00:10:52 --> 00:10:55 2023. Eight year cruise in August
00:10:55 --> 00:10:57 2024. It did something nobody had done
00:10:57 --> 00:11:00 before. A gravity assist off the moon. And
00:11:00 --> 00:11:02 then Earth, 336 hours apart.
00:11:02 --> 00:11:05 Venus in August 2025. This is
00:11:05 --> 00:11:07 Earth number two. Earth number three is
00:11:07 --> 00:11:10 January 2029. And then Jupiter in
00:11:10 --> 00:11:13 July 2031 where it makes
00:11:13 --> 00:11:15 35 flybys of the big moons before
00:11:15 --> 00:11:18 settling into orbit around Ganymede.
00:11:18 --> 00:11:20 Avery: And one small coincidence for the diary,
00:11:21 --> 00:11:23 Starship's Flight 14 is currently
00:11:23 --> 00:11:26 targeted to 12:15 UTC that
00:11:26 --> 00:11:29 same Monday. Juice's closest approach is
00:11:29 --> 00:11:32 11:45, half an hour apart on
00:11:32 --> 00:11:34 opposite sides of the planet in opposite
00:11:34 --> 00:11:34 directions.
00:11:35 --> 00:11:37 Anna: Alright, moving on to our next storey.
00:11:38 --> 00:11:41 HR 8799 is the system that
00:11:41 --> 00:11:43 made direct imaging of exoplanets
00:11:43 --> 00:11:46 real.4 giant planets photographed
00:11:46 --> 00:11:48 as actual points of light orbiting a uh,
00:11:48 --> 00:11:51 young star between a warm inner belt of
00:11:51 --> 00:11:53 debris and a cold outer ring.
00:11:53 --> 00:11:56 It's the benchmark. And for years there's
00:11:56 --> 00:11:58 been a hole in it, a region a few
00:11:58 --> 00:12:01 astronomical units out, too close in for
00:12:01 --> 00:12:03 conventional high contrast imaging to
00:12:03 --> 00:12:05 resolve. And very hard for the radial
00:12:05 --> 00:12:08 velocity method because the star itself
00:12:08 --> 00:12:11 pulsates and smears the signal. People have
00:12:11 --> 00:12:13 long suspected something is in there. The
00:12:13 --> 00:12:16 inner edge of that warm belt sits at about
00:12:16 --> 00:12:19 five to six astronomical units, well
00:12:19 --> 00:12:21 inside the orbit of the innermost known
00:12:21 --> 00:12:23 planet. Something appears to be sweeping it.
00:12:24 --> 00:12:26 Avery: And this month two groups went at it from
00:12:26 --> 00:12:27 opposite directions.
00:12:28 --> 00:12:31 Anna: They did. And the honest headline is both of
00:12:31 --> 00:12:34 them see something and they do not obviously
00:12:34 --> 00:12:36 agree about what it is. The first
00:12:36 --> 00:12:39 posted on 9th September is led by Jake
00:12:39 --> 00:12:42 Nguyen with a large team. They went back
00:12:42 --> 00:12:45 to archival JWST data taken with
00:12:45 --> 00:12:47 the aperture masking interometer and
00:12:47 --> 00:12:50 reprocessed it with a new pipeline. They find
00:12:50 --> 00:12:53 a source sitting just above their 3 sigma
00:12:53 --> 00:12:56 contrast curve at a projected separation of
00:12:56 --> 00:12:59 about 150 milliarcseconds which
00:12:59 --> 00:13:02 works out to roughly 7 astronomical units
00:13:02 --> 00:13:04 and a few to several Jupiter masses.
00:13:05 --> 00:13:08 And its position sits near a stable orbital
00:13:08 --> 00:13:10 solution for a fifth planet in a three to one
00:13:10 --> 00:13:13 resonance with the innermost known planet.
00:13:13 --> 00:13:15 Avery: And um, this is where it becomes an
00:13:15 --> 00:13:17 Australian storey in a way that I did not
00:13:17 --> 00:13:18 expect.
00:13:18 --> 00:13:21 Anna: The aperture masking interometer is the only
00:13:21 --> 00:13:23 piece of Australian designed hardware on the
00:13:23 --> 00:13:26 James Webb Space Telescope. It was created
00:13:26 --> 00:13:28 by Professor Peter Toothhill at the
00:13:28 --> 00:13:31 University of Sydney. It works by masking
00:13:31 --> 00:13:34 the telescope's mirror down to a handful of
00:13:34 --> 00:13:37 patches and combining their light which buys
00:13:37 --> 00:13:40 you resolution right in close to a bright
00:13:40 --> 00:13:42 star, exactly where this planet would be.
00:13:43 --> 00:13:45 And the pipeline that made this detection
00:13:45 --> 00:13:47 possible came out of that same group.
00:13:48 --> 00:13:50 Sydney PhD students built a software
00:13:50 --> 00:13:53 only calibration system to correct a
00:13:53 --> 00:13:55 detector effect that had been quietly
00:13:55 --> 00:13:58 blurring AMI's images and recovered
00:13:58 --> 00:14:01 the instrument's full sensitivity without
00:14:01 --> 00:14:04 anyone leaving the ground. The paper says in
00:14:04 --> 00:14:06 plain terms that the Detection was enabled by
00:14:06 --> 00:14:09 a pipeline accounting for the systematics
00:14:09 --> 00:14:11 that limited earlier analyses.
00:14:11 --> 00:14:14 That is the Sydney Fix doing the job it was
00:14:14 --> 00:14:17 built for. The second paper landed on Monday
00:14:17 --> 00:14:19 led by Anne Marie Lagrange, and it's
00:14:19 --> 00:14:22 submitted to Nature Astronomy. Completely
00:14:22 --> 00:14:24 different approach. Gaia's absolute
00:14:24 --> 00:14:27 astronomy combined with proper motion
00:14:27 --> 00:14:29 anomalies between Hipparcos and Gaia,
00:14:29 --> 00:14:32 plus radial velocities and imaging.
00:14:32 --> 00:14:35 They're not photographing anything, they're
00:14:35 --> 00:14:38 watching the star get tugged. Their allowed
00:14:38 --> 00:14:40 solutions span roughly a third of an
00:14:40 --> 00:14:43 astronomical unit out to 6, with the
00:14:43 --> 00:14:45 probability peaking at 2 to 3 and
00:14:45 --> 00:14:48 masses of about 10 to 14 jupiters.
00:14:48 --> 00:14:51 They also show that an object like that on a
00:14:51 --> 00:14:54 low eccentricity orbit can coexist with
00:14:54 --> 00:14:57 the long lived resonant chain of the four
00:14:57 --> 00:15:00 known planets and sculpt that inner belt
00:15:00 --> 00:15:00 edge.
00:15:00 --> 00:15:02 Avery: Next, the honest reading.
00:15:03 --> 00:15:05 Anna: So 7 astronomical units and a few
00:15:05 --> 00:15:08 Jupiter masses versus 2 to 3 and 10
00:15:08 --> 00:15:11 to 14. Those are not the same object
00:15:11 --> 00:15:14 as stated. They may be the same object with
00:15:14 --> 00:15:16 wide error bars or two different
00:15:16 --> 00:15:19 detections, or one of them may not survive.
00:15:19 --> 00:15:22 Both are preprints. Neither has been through
00:15:22 --> 00:15:24 peer review. This is a candidate and we've
00:15:24 --> 00:15:27 been here before. You'll remember from last
00:15:27 --> 00:15:29 week how contested the history of directly
00:15:29 --> 00:15:31 imaged protoplanets is.
00:15:31 --> 00:15:34 And for the observers, HR
00:15:34 --> 00:15:36 8799 is at declination
00:15:37 --> 00:15:39 21. It transits nearly
00:15:39 --> 00:15:42 77 degrees up from Los Angeles and
00:15:42 --> 00:15:45 about 71 from New York. From here in
00:15:45 --> 00:15:48 Sydney it barely clears 35. This one
00:15:48 --> 00:15:49 belongs to the north.
00:15:49 --> 00:15:51 Avery: We've been holding this one for a couple of
00:15:51 --> 00:15:52 weeks, waiting for the right slot.
00:15:52 --> 00:15:55 So here it is at last. Back in March, a
00:15:55 --> 00:15:57 team led by Martin Cordiner published a
00:15:57 --> 00:16:00 measurement of the water in 3I ATLAS,
00:16:00 --> 00:16:03 the third interstellar object ever found
00:16:03 --> 00:16:04 passing through our solar system.
00:16:05 --> 00:16:07 Specifically, they measured its deuterium to
00:16:07 --> 00:16:10 hydrogen ratio. Deuterium is heavy
00:16:10 --> 00:16:13 hydrogen, an ordinary hydrogen atom with a
00:16:13 --> 00:16:16 neutron added. And the ratio of heavy water
00:16:16 --> 00:16:18 to ordinary water in a comet is one of the
00:16:18 --> 00:16:21 most useful fingerprints we have because it's
00:16:21 --> 00:16:23 set by how cold it was and what was around
00:16:24 --> 00:16:25 when that ice first formed.
00:16:26 --> 00:16:28 Anna: And three I ATLAS came back high.
00:16:29 --> 00:16:31 Avery: And the paper we are covering Today, posted
00:16:31 --> 00:16:33 on 14th September by a team including
00:16:34 --> 00:16:36 Kenji Furuya, Cordiner himself
00:16:36 --> 00:16:39 and Dominique Bocole Morven, is the
00:16:39 --> 00:16:42 attempt to explain why. I want to be very
00:16:42 --> 00:16:44 clear about what this is because the framing
00:16:44 --> 00:16:47 matters. This is not a new measurement.
00:16:47 --> 00:16:50 Nobody pointed a telescope at anything. This
00:16:50 --> 00:16:52 is a modelling paper working out what
00:16:52 --> 00:16:54 conditions could produce the ratio that Was
00:16:54 --> 00:16:57 already measured in March and there is no
00:16:57 --> 00:16:59 institutional press release behind it. It is
00:16:59 --> 00:17:01 a preprint eight days old.
00:17:01 --> 00:17:03 Anna: So what does the model say?
00:17:03 --> 00:17:06 Avery: Their conclusion is that the high ratio is
00:17:06 --> 00:17:08 consistent with three I ATLs
00:17:09 --> 00:17:11 forming around a star with low met
00:17:11 --> 00:17:13 metallicity. Meaning a star poor in elements
00:17:13 --> 00:17:16 heavier than hydrogen and helium. Which in
00:17:16 --> 00:17:19 practise tends to mean an old star. An
00:17:19 --> 00:17:21 object assembled in a different chemical
00:17:21 --> 00:17:23 environment from the one that built our own
00:17:23 --> 00:17:25 comets. And it slots neatly against the
00:17:25 --> 00:17:27 result. We covered a couple of weeks back the
00:17:27 --> 00:17:30 first ion inventory of an interstellar
00:17:30 --> 00:17:32 object's tail out of Northumbria and
00:17:32 --> 00:17:35 Edinburgh, which found enough molecular
00:17:35 --> 00:17:37 nitrogen relative to carbon monoxide to
00:17:37 --> 00:17:40 imply this thing formed below about 3030
00:17:40 --> 00:17:43 Kelvin. Very cold and a long way from
00:17:43 --> 00:17:43 its star.
00:17:44 --> 00:17:46 Anna: Two independent lines pointing the same
00:17:46 --> 00:17:47 direction.
00:17:47 --> 00:17:50 Avery: Two independent lines, and they are genuinely
00:17:50 --> 00:17:53 independent. One is ions in a plasma
00:17:53 --> 00:17:55 tail, the other is heavy water. But the
00:17:55 --> 00:17:58 caveat is the same caveat as always with
00:17:58 --> 00:18:01 D2H. It is a tracer, not a direct
00:18:01 --> 00:18:01 reading.
00:18:01 --> 00:18:04 Converting a ratio into a birthplace runs
00:18:04 --> 00:18:05 through a chain of assumptions about
00:18:05 --> 00:18:08 chemistry and temperature. And this paper is
00:18:08 --> 00:18:10 exploring that chain rather than closing it.
00:18:11 --> 00:18:13 The Southern Note, as ever with this object,
00:18:13 --> 00:18:16 three I ATLS was discovered by the
00:18:16 --> 00:18:19 ATLAS Survey telescope at ah Rio Urtado in
00:18:19 --> 00:18:21 Chile. Whatever we end up learning about the
00:18:21 --> 00:18:24 star that made it, the first person to see it
00:18:24 --> 00:18:26 was looking up from the southern hemisphere.
00:18:26 --> 00:18:29 Anna: Now, three quick ones. All dates.
00:18:29 --> 00:18:32 Starship Flight 14 is still targeted for
00:18:32 --> 00:18:35 Monday 28 September 1215
00:18:35 --> 00:18:38 UTC. That's 10:15 on Monday evening,
00:18:38 --> 00:18:40 Eastern Standard Time here. The booster has
00:18:40 --> 00:18:42 been rolled out to the pad and the ship has
00:18:42 --> 00:18:45 been test fired. You will remember we had to
00:18:45 --> 00:18:47 correct ourselves on this flight once already
00:18:47 --> 00:18:49 when it moved off the 22nd.
00:18:50 --> 00:18:53 So we're saying targeted, not scheduled. And
00:18:53 --> 00:18:54 we'll believe it when the clock runs.
00:18:55 --> 00:18:58 Avery: NASA's own mission page still reads no
00:18:58 --> 00:19:00 earlier than early October. Not a date, a
00:19:00 --> 00:19:03 window. The crew went to quarantine on the
00:19:03 --> 00:19:05 17th, which is the normal run up. And the
00:19:05 --> 00:19:08 oxidizer valve that caused the original stand
00:19:08 --> 00:19:10 down was replaced weeks ago. There are
00:19:10 --> 00:19:12 specific dates circulating on unofficial
00:19:12 --> 00:19:14 trackers. We are not going to read you a date
00:19:14 --> 00:19:16 that NASA has not published.
00:19:16 --> 00:19:19 Anna: And Albania has signed the Artemis Accords.
00:19:19 --> 00:19:22 That happened on Monday at NASA headquarters.
00:19:22 --> 00:19:24 Foreign Minister Fareed Hoxha signing for
00:19:24 --> 00:19:27 Albania. Deputy Administrator Matt Anderson
00:19:27 --> 00:19:29 for NASA Albania becomes the
00:19:29 --> 00:19:31 73rd signatory.
00:19:31 --> 00:19:34 Avery: 73. It was 50 something not that long
00:19:34 --> 00:19:35 ago it was.
00:19:36 --> 00:19:38 Anna: And whatever you make of the Accords as an
00:19:38 --> 00:19:40 instrument, and there's a real Debate there
00:19:40 --> 00:19:42 about whether they substitute for treaty
00:19:42 --> 00:19:45 making. The sheer rate of accession is now
00:19:45 --> 00:19:46 the storey in itself.
00:19:46 --> 00:19:49 Avery: Moving on to Skywatch, let's start with the
00:19:49 --> 00:19:51 moment this episode goes out, because it's a
00:19:51 --> 00:19:54 moment, not a day. The September equinox
00:19:54 --> 00:19:56 falls at five minutes past midnight utc.
00:19:57 --> 00:19:59 That's five past ten in the morning on
00:19:59 --> 00:20:01 Wednesday for us in Sydney. So it happens
00:20:01 --> 00:20:03 while you're listening to this. In London,
00:20:03 --> 00:20:05 it's just after one in the morning on the
00:20:05 --> 00:20:08 23rd, but in New York, it's five past eight
00:20:08 --> 00:20:11 on the evening of the 22nd, and in Los
00:20:11 --> 00:20:13 Angeles, five past five that same afternoon.
00:20:14 --> 00:20:16 Anna: So half our audience had their equinox
00:20:16 --> 00:20:17 yesterday.
00:20:17 --> 00:20:20 Avery: Exactly. And that is not a quirk, it is the
00:20:20 --> 00:20:23 point. An, um, equinox is an instant, not
00:20:23 --> 00:20:26 a date. It is one specific moment when
00:20:26 --> 00:20:29 the sun crosses the celestial equator. And
00:20:29 --> 00:20:31 what calendar date that lands on depends
00:20:31 --> 00:20:34 entirely on where you are standing. We have
00:20:34 --> 00:20:37 said the 22nd in past episodes and for North
00:20:37 --> 00:20:40 America, that was right. For Australia, it is
00:20:40 --> 00:20:42 the 23rd. The thing to actually plan for
00:20:42 --> 00:20:43 is Monday.
00:20:43 --> 00:20:46 As we said earlier, Juice crosses Australia
00:20:46 --> 00:20:49 between about 9:15 and 9:30 in the
00:20:49 --> 00:20:51 evening Eastern time. Northeast to
00:20:51 --> 00:20:54 northwest in a fully dark sky from
00:20:54 --> 00:20:56 coast to coast. Telescope or good
00:20:56 --> 00:20:59 binoculars and current coordinates cheque
00:20:59 --> 00:21:01 ESA's own pages on the day, because the
00:21:01 --> 00:21:03 ephemeris will be refined right up to the
00:21:03 --> 00:21:04 flyby.
00:21:04 --> 00:21:06 Anna: For, uh, our northern listeners, this one is
00:21:06 --> 00:21:08 not yours. Closest to approaches over the
00:21:08 --> 00:21:10 Indian Ocean in the middle of your day.
00:21:10 --> 00:21:10 Sorry.
00:21:11 --> 00:21:14 Avery: Turning to the evening sky, Venus is still
00:21:14 --> 00:21:17 the standout after sunset and the gap between
00:21:17 --> 00:21:20 hemispheres is as wide as it's been all year.
00:21:20 --> 00:21:23 From Sydney, Venus sits 36 degrees above the
00:21:23 --> 00:21:26 horizon at sunset and stays up for three
00:21:26 --> 00:21:28 hours and one minute after the sun goes down.
00:21:29 --> 00:21:32 From Los Angeles, 12 degrees and gone in an
00:21:32 --> 00:21:35 hour and nine minutes. New York, 8 degrees,
00:21:35 --> 00:21:37 54 minutes. London, um, 2
00:21:37 --> 00:21:40 degrees and 20 minutes, which in practise
00:21:40 --> 00:21:43 means a clear, flat western horizon or
00:21:43 --> 00:21:44 nothing at all.
00:21:44 --> 00:21:47 Anna: And that is the ecliptic angle again.
00:21:48 --> 00:21:50 Avery: Same geometry we've talked about all spring.
00:21:50 --> 00:21:53 Around the equinox, the ecliptic stands up
00:21:53 --> 00:21:55 almost vertically from the western horizon in
00:21:55 --> 00:21:58 the southern hemisphere and lies down almost
00:21:58 --> 00:22:01 flat in the north. Same planet,
00:22:01 --> 00:22:03 same evening, completely different
00:22:03 --> 00:22:03 experience.
00:22:04 --> 00:22:07 Mercury is doing the same thing. Eighteen and
00:22:07 --> 00:22:09 a half degrees up from Sydney at sunset,
00:22:10 --> 00:22:12 three and a half from London, southern
00:22:12 --> 00:22:13 object.
00:22:13 --> 00:22:16 Anna: The Moon is a waxing gibbous, about 86%
00:22:16 --> 00:22:18 lit on Wednesday evening, and it's heading
00:22:18 --> 00:22:21 for full at 4:48 in the afternoon UTC
00:22:21 --> 00:22:24 on the 26th. Note the calendar split on that
00:22:24 --> 00:22:26 one. That instant is 10 to 3 in the morning
00:22:26 --> 00:22:29 of the 27th in Sydney. So Australian
00:22:29 --> 00:22:31 calendars will say Sunday and northern ones
00:22:31 --> 00:22:34 will say Saturday. It looks full both nights
00:22:34 --> 00:22:34 either way.
00:22:35 --> 00:22:38 Avery: Saturn rises at about 20 to 7 in the evening
00:22:38 --> 00:22:41 from Sydney and is 54 degree up, uh six hours
00:22:41 --> 00:22:43 later. It's heading for opposition in the
00:22:43 --> 00:22:45 first week of October. And as we worked out
00:22:45 --> 00:22:48 last week, the two standard definitions put
00:22:48 --> 00:22:50 it on the 4th and the 5th. Both are
00:22:50 --> 00:22:53 legitimate. It doesn't matter. The brightness
00:22:53 --> 00:22:55 holds at magnitude 0.32 and
00:22:55 --> 00:22:58 the disc at 19.6 arc seconds
00:22:58 --> 00:23:01 right across that week. So there's no wrong
00:23:01 --> 00:23:03 night. And now the counterweight because
00:23:03 --> 00:23:06 today's storeys have leaned north and the pre
00:23:06 --> 00:23:07 dawn sky does too.
00:23:08 --> 00:23:11 Mars at nautical dawn, 50 degrees up from Los
00:23:11 --> 00:23:14 Angeles, 48 from New York, 42
00:23:14 --> 00:23:17 from London and 21 from Sydney.
00:23:17 --> 00:23:20 Jupiter 30 degrees from Los Angeles and 10
00:23:20 --> 00:23:23 and a half from here. The two of them are 20
00:23:23 --> 00:23:26 and a half degrees apart and closing through
00:23:26 --> 00:23:28 Anna: spring, which is the tie back to the lead.
00:23:29 --> 00:23:31 Avery: It is if you want to look at the planet. We
00:23:31 --> 00:23:33 spent eight minutes on this morning and you
00:23:33 --> 00:23:36 are in the northern hemisphere. It's 50
00:23:36 --> 00:23:38 degrees up before sunrise and easy.
00:23:39 --> 00:23:41 Jezero crater is at 18 degrees north on
00:23:41 --> 00:23:44 Mars. So even the geology is northern today.
00:23:44 --> 00:23:46 Some weeks it runs the other way.
00:23:46 --> 00:23:48 Last Monday we gave the south the better
00:23:48 --> 00:23:51 geometry and the north the deep sky. Today
00:23:51 --> 00:23:54 the north has the science, the planets and
00:23:54 --> 00:23:57 the October occultation. And the south has
00:23:57 --> 00:23:59 Venus, Mercury and a uh, spacecraft going
00:23:59 --> 00:24:01 overhead on Monday night.
00:24:01 --> 00:24:03 Anna: And the standing reminder because we say it
00:24:03 --> 00:24:06 every single episode and we are not going to
00:24:06 --> 00:24:09 stop. If you are observing the sun at
00:24:09 --> 00:24:11 any point, for any reason, at any stage,
00:24:12 --> 00:24:15 you need filters certified to ISO
00:24:15 --> 00:24:18 123122. That
00:24:18 --> 00:24:21 is the international standard for safe solar
00:24:21 --> 00:24:23 viewing. Sunglasses are not adequate.
00:24:23 --> 00:24:26 Stacked sunglasses are not adequate.
00:24:26 --> 00:24:29 Exposed film, smoked glass, a
00:24:29 --> 00:24:32 welding filter below shade 14, none
00:24:32 --> 00:24:35 of those are adequate. And never ever
00:24:35 --> 00:24:37 look at the sun through a telescope,
00:24:37 --> 00:24:39 binoculars or a camera lens that does not
00:24:39 --> 00:24:42 have a purpose made solar filter fitted over
00:24:42 --> 00:24:43 the front.
00:24:43 --> 00:24:46 A filter that screws into the eyepiece can
00:24:46 --> 00:24:48 crack under the heat front of the optic.
00:24:48 --> 00:24:50 Certified every time.
00:24:50 --> 00:24:52 Avery: That's Astronomy AstroDailyPod for today.
00:24:53 --> 00:24:56 Anna: Three floods at the edge of Jezero Crater.
00:24:56 --> 00:24:59 Groundwater, then a lake, then hot water from
00:24:59 --> 00:25:01 below. Red out of rock that was not
00:25:01 --> 00:25:03 supposed to be there at all.
00:25:04 --> 00:25:06 Avery: Juice coming home on Monday nights and 15
00:25:06 --> 00:25:08 minutes of uh, it belonging to
00:25:08 --> 00:25:11 Anna: Australia, a candidate fifth planet
00:25:11 --> 00:25:14 at HR 8799. Found
00:25:14 --> 00:25:16 two different ways by two teams who do not
00:25:16 --> 00:25:19 quite agree with an Australian instrument and
00:25:19 --> 00:25:22 an Australian software fix in the middle of
00:25:22 --> 00:25:22 one of them
00:25:23 --> 00:25:25 Avery: and heavy water in an interstellar comet
00:25:25 --> 00:25:28 pointing at an old metopore star we will
00:25:28 --> 00:25:29 never see.
00:25:29 --> 00:25:32 And one small thing before we go this is
00:25:32 --> 00:25:33 episode 200 for the year.
00:25:34 --> 00:25:37 Anna: 200 episodes this year alone.
00:25:37 --> 00:25:40 Not many shows can say that and fewer still
00:25:40 --> 00:25:42 can say it without the quality going out the
00:25:42 --> 00:25:44 window somewhere around episode 60.
00:25:45 --> 00:25:48 Avery: That is not an accident and it is not one
00:25:48 --> 00:25:50 person. That is a team turning this around
00:25:50 --> 00:25:53 day after day and holding the standard while
00:25:53 --> 00:25:55 they do it. Thank you to everyone who makes
00:25:55 --> 00:25:58 it happen and thank you for listening to all
00:25:58 --> 00:25:58 200 of them.
00:25:59 --> 00:26:01 Anna: Astronomy AstroDailyPod is produced in
00:26:01 --> 00:26:03 Sydney. You'll find every episode, the show
00:26:03 --> 00:26:06 notes and the newsletter at astronomydaily
00:26:06 --> 00:26:09 IO and we're AstroDaily
00:26:09 --> 00:26:10 Pod on the socials.
00:26:10 --> 00:26:11 Avery: We're back tomorrow.
00:26:12 --> 00:26:13 Anna: Until then, Clear Skies.
00:26:23 --> 00:26:23 Avery: Mhm.
00:26:25 --> 00:26:25 Anna: The storey.