Become a supporter of this podcast: https://www.spreaker.com/podcast/astronomy-daily-latest-space-news--5648921/support.
Sponsor Details:
Ensure your online privacy by using NordVPN. To get our special listener deal and save a lot of money, visit www.astronomydaily.io/nordvpn. You'll be glad you did!
Get the best secure and private email on the planet. Stop your Government, google and who knows who else spying on every email you write. Do what we did and use ProtonMail. They beleive in privacy and there are no ads in their business model...yet they still provide a free forever service. Check them out and get out special deal at www.astronomydaily.io/protonmail
Become a supporter of Astronomy Daily by joining our Supporters Club. Commercial free episodes daily are only a click way... Click Here
This episode includes AI-generated content.
00:00:00 --> 00:00:03 Anna: Hey, everyone. Welcome back to Astronomy
00:00:03 --> 00:00:05 daily. It's Wednesday, September 2nd,
00:00:05 --> 00:00:08 series five, episode 183.
00:00:08 --> 00:00:11 Avery: And today we've got a genuinely lovely piece
00:00:11 --> 00:00:13 of planetary science to lead with, which
00:00:13 --> 00:00:14 doesn't happen every day.
00:00:15 --> 00:00:16 Anna: It really is a good one.
00:00:17 --> 00:00:19 There's something hot buried under Mars's
00:00:19 --> 00:00:21 south pole. And I mean that literally.
00:00:22 --> 00:00:23 Avery: Bolton.
00:00:23 --> 00:00:26 Anna: Even Bolton. A new Nature
00:00:26 --> 00:00:28 paper says the southern half of Mars's
00:00:28 --> 00:00:30 interior is hundreds of degrees hotter than
00:00:30 --> 00:00:33 the northern half. And it might finally
00:00:33 --> 00:00:35 explain the single weirdest thing about that
00:00:35 --> 00:00:36 planet.
00:00:36 --> 00:00:39 Avery: Then Crew 13 is standing down after a leak
00:00:39 --> 00:00:42 turned up in Dragon. NASA's Swift telescope
00:00:42 --> 00:00:45 is observing again, but now it's in a race
00:00:45 --> 00:00:47 with the atmosphere. And the Seattle
00:00:47 --> 00:00:49 nonprofit wants to launch a spacecraft to
00:00:49 --> 00:00:52 Alpha Centauri that won't arrive for
00:00:52 --> 00:00:53 80 years.
00:00:53 --> 00:00:55 Anna: They're aware of that, by the way. That's the
00:00:55 --> 00:00:55 pitch.
00:00:56 --> 00:00:59 Avery: That is very much the pitch. Then we'll get
00:00:59 --> 00:01:02 you sorted for tonight's sky. Five planets
00:01:02 --> 00:01:04 are in play this month. North and south.
00:01:04 --> 00:01:05 Anna: Let's get into it.
00:01:06 --> 00:01:09 Avery: Okay, Set this up properly for me because I
00:01:09 --> 00:01:11 want to understand what was actually found.
00:01:11 --> 00:01:13 Anna: So this is a paper published in nature on
00:01:13 --> 00:01:16 August 27, titled, and I love
00:01:16 --> 00:01:19 this title. Title. Tomography Reveals a
00:01:19 --> 00:01:22 Thermal anomaly beneath Mars's Crustal
00:01:22 --> 00:01:24 Dichotomy. Lead author is Alexander
00:01:24 --> 00:01:27 Byrne, who did this as his PhD work at
00:01:27 --> 00:01:30 Caltech and has just moved to the University
00:01:30 --> 00:01:31 of Arizona.
00:01:31 --> 00:01:33 Avery: And the finding, in one sentence, the
00:01:33 --> 00:01:36 Anna: inside of Mars's southern hemisphere is
00:01:36 --> 00:01:39 somewhere between 200 and 400
00:01:39 --> 00:01:42 degrees Celsius, hotter than the inside of
00:01:42 --> 00:01:44 its northern hemisphere and parts of it are
00:01:44 --> 00:01:46 partially molten.
00:01:46 --> 00:01:49 Avery: Two to 400 degrees is not a
00:01:49 --> 00:01:50 subtle difference.
00:01:50 --> 00:01:53 Anna: It's enormous. This isn't a hot spot or
00:01:53 --> 00:01:56 a plume. This is one half of a planet's
00:01:56 --> 00:01:59 interior running fundamentally hotter than
00:01:59 --> 00:02:01 the other half and staying that way over
00:02:01 --> 00:02:02 geologic time.
00:02:03 --> 00:02:04 Avery: Before we get to how they measured that,
00:02:05 --> 00:02:06 explain the thing it might solve.
00:02:06 --> 00:02:09 You said the weirdest thing about Mars,
00:02:09 --> 00:02:12 Anna: the Martian crustal dichotomy. If
00:02:12 --> 00:02:14 you've ever looked at one of those false
00:02:14 --> 00:02:16 colour topographic maps of Mars, you'll have
00:02:16 --> 00:02:19 seen it immediately, even if nobody named it
00:02:19 --> 00:02:21 for you. The northern third of the planet is
00:02:21 --> 00:02:24 smooth, low lying, young looking plains.
00:02:24 --> 00:02:27 The southern two thirds is high, ancient,
00:02:27 --> 00:02:30 heavily cratered highlands on crust that's
00:02:30 --> 00:02:33 substantially thicker. And the boundary
00:02:33 --> 00:02:36 between them is remarkably sharp, a step
00:02:36 --> 00:02:38 of several kilometres in elevation in places.
00:02:39 --> 00:02:40 Avery: How long has that been sitting there,
00:02:40 --> 00:02:41 unexplained?
00:02:41 --> 00:02:44 Anna: It's sitting there since the Viking orbiters
00:02:44 --> 00:02:46 mapped it in the 70s. 50 years
00:02:47 --> 00:02:49 it's genuinely one of the oldest open
00:02:49 --> 00:02:51 questions in planetary science.
00:02:52 --> 00:02:54 Avery: So it's not just a surface feature, it goes
00:02:54 --> 00:02:54 deep.
00:02:55 --> 00:02:57 Anna: That's the point of this paper. The dichotomy
00:02:57 --> 00:03:00 isn't paint on the outside. The it appears to
00:03:00 --> 00:03:02 have a matching structure hundreds of
00:03:02 --> 00:03:05 kilometres down in the mantle. The hemisphere
00:03:05 --> 00:03:08 that looks different on the surface is also
00:03:08 --> 00:03:10 the hemisphere that's hotter underneath.
00:03:10 --> 00:03:13 Avery: Okay, so how do you take the temperature of
00:03:13 --> 00:03:15 another planet? We've got exactly one
00:03:15 --> 00:03:17 seismometer that's ever operated on Mars and
00:03:17 --> 00:03:18 it's dead now.
00:03:19 --> 00:03:21 Anna: This is the part I find really clever.
00:03:21 --> 00:03:24 They didn't use seismology at all. They used
00:03:24 --> 00:03:27 the fact that Mars flexes. Lex's
00:03:27 --> 00:03:30 Howe the sun pulls on Mars the way
00:03:30 --> 00:03:33 the moon pulls on Earth's oceans, tides.
00:03:33 --> 00:03:36 Mars has no oceans. But the whole solid
00:03:36 --> 00:03:38 planet still stretches and relaxes
00:03:39 --> 00:03:42 very slightly on every orbit. And how much
00:03:42 --> 00:03:45 it flexes depends on what it's made of and
00:03:45 --> 00:03:47 critically, how hot and soft its interior
00:03:47 --> 00:03:50 is. Hot, partially molten rock
00:03:50 --> 00:03:53 deforms more easily than cold rigid rock.
00:03:53 --> 00:03:55 Avery: So the amount of squish tells you
00:03:55 --> 00:03:58 Anna: the temperature, the amount of squish tells
00:03:58 --> 00:04:01 you the temperature. It's a tiny effect, but
00:04:01 --> 00:04:03 a planet that changes shape has a gravity
00:04:03 --> 00:04:06 field that changes with it. And we've had
00:04:06 --> 00:04:09 spacecraft orbiting Mars continuously for
00:04:09 --> 00:04:12 decades, all tracked by radio from Earth.
00:04:12 --> 00:04:15 Avery: So the spacecraft are the instrument, the
00:04:15 --> 00:04:18 Anna: spacecraft are the instrument. Burns team
00:04:18 --> 00:04:20 went back through tracking data from Mars
00:04:20 --> 00:04:23 Global Surveyor, Mars Odyssey and Mars
00:04:23 --> 00:04:26 Reconnaissance Orbiter. 25 years of it,
00:04:26 --> 00:04:29 looking at the minute velocity changes as
00:04:29 --> 00:04:31 each one flew over different parts of the
00:04:31 --> 00:04:34 planet. Those wiggles map the gravity field.
00:04:34 --> 00:04:36 And the way that field breathes across a
00:04:36 --> 00:04:38 martian year maps the flex.
00:04:39 --> 00:04:41 Avery: And nobody had done that before, not
00:04:41 --> 00:04:44 Anna: to this resolution and not with the aim of
00:04:44 --> 00:04:46 separating one hemisphere from the other.
00:04:46 --> 00:04:49 That's what the tomography in the title is
00:04:49 --> 00:04:51 doing. Same word as a medical CT scan.
00:04:51 --> 00:04:54 Roughly the same idea. Lots of measurements
00:04:54 --> 00:04:57 from lots of angles reconstructed into a
00:04:57 --> 00:04:58 picture of the inside.
00:04:59 --> 00:05:02 Avery: 25 years of data collected by missions
00:05:02 --> 00:05:03 that weren't launched to do this.
00:05:04 --> 00:05:06 Anna: Mars Global surveyor launched in
00:05:06 --> 00:05:09 1996 and stopped talking to us in
00:05:09 --> 00:05:11 2006. And its tracking data is still
00:05:11 --> 00:05:14 producing new results 20 years later.
00:05:14 --> 00:05:17 It's a good argument for archiving everything
00:05:17 --> 00:05:19 forever. And this is a big international
00:05:20 --> 00:05:22 effort. Co authors across Brown,
00:05:22 --> 00:05:25 NASA Goddard, Arizona, Academia
00:05:25 --> 00:05:28 Sinica in Taiwan, the University of Rome,
00:05:28 --> 00:05:31 Delft, ucla, UT Austin,
00:05:31 --> 00:05:34 Colorado, Boulder and UC Santa Cruz.
00:05:34 --> 00:05:37 Avery: So what else does this hot southern interior
00:05:37 --> 00:05:37 explain?
00:05:38 --> 00:05:40 Anna: Two things that have been nagging at people.
00:05:40 --> 00:05:43 First, magnetism. Mars has no global
00:05:43 --> 00:05:46 magnetic field today. But the crust is
00:05:46 --> 00:05:49 magnetised in patches, frozen in evidence
00:05:49 --> 00:05:51 of a field that switched off billions of
00:05:51 --> 00:05:53 years ago. And those anomalies are
00:05:53 --> 00:05:56 overwhelmingly concentrated in the southern
00:05:56 --> 00:05:58 highlands. A hemisphere with a, uh, different
00:05:58 --> 00:06:00 thermal history from the start would
00:06:00 --> 00:06:02 magnetise differently and hold that record
00:06:02 --> 00:06:03 differently.
00:06:03 --> 00:06:04 Avery: And the second.
00:06:05 --> 00:06:08 Anna: The second seismic, when Insight was
00:06:08 --> 00:06:10 operating its seismometer, found waves
00:06:10 --> 00:06:13 passing through parts of Mars interior were
00:06:13 --> 00:06:15 damped from far more strongly than expected.
00:06:16 --> 00:06:18 Waves lose energy fast in hot soft
00:06:18 --> 00:06:21 material. Exactly what partially molten
00:06:21 --> 00:06:23 rock down there would produce.
00:06:23 --> 00:06:26 Avery: So it's not one line of evidence. It makes
00:06:26 --> 00:06:27 three separate puzzles line up.
00:06:28 --> 00:06:31 Anna: That's what makes it feel solid. Any one
00:06:31 --> 00:06:33 on its own you'd want it replicated. All, ah,
00:06:33 --> 00:06:35 three pointing the same way is more
00:06:35 --> 00:06:36 persuasive.
00:06:37 --> 00:06:39 Avery: Do we know why the southern half ended up
00:06:39 --> 00:06:39 hotter?
00:06:40 --> 00:06:42 Anna: Oh, and the team is upfront about that. Three
00:06:42 --> 00:06:45 families of explanation. One, a, uh, giant
00:06:45 --> 00:06:48 impact early in Mars's history. Something
00:06:48 --> 00:06:50 enormous hitting the northern hemisphere,
00:06:50 --> 00:06:53 blasting out the lowlands and rearranging the
00:06:53 --> 00:06:56 interior. Two, mantle convection that
00:06:56 --> 00:06:58 settled into a lopsided pattern and stayed
00:06:58 --> 00:07:01 there. Which planetary interiors genuinely
00:07:01 --> 00:07:04 can do. Three, something compositional.
00:07:04 --> 00:07:06 A layer enriched in radioactive elements
00:07:06 --> 00:07:08 generating its own heat.
00:07:08 --> 00:07:10 Avery: And this result doesn't pick between them.
00:07:11 --> 00:07:13 Anna: Not yet. What it does is hand you a hard
00:07:13 --> 00:07:16 number. Every explanation now has to
00:07:16 --> 00:07:18 reproduce. Before this, why is Mars
00:07:18 --> 00:07:21 lopsided? Was mostly a surface geology
00:07:21 --> 00:07:24 question. Now it's a question about the whole
00:07:24 --> 00:07:26 planet with a temperature constraint
00:07:26 --> 00:07:26 attached.
00:07:27 --> 00:07:29 Avery: Does this connect to the water storey? That's
00:07:29 --> 00:07:31 usually where Mars questions, um, end up.
00:07:31 --> 00:07:34 Anna: It does. And it's the line from the team I
00:07:34 --> 00:07:37 keep coming back to. The dichotomy matters
00:07:37 --> 00:07:39 because it tells you about the processes that
00:07:39 --> 00:07:41 shaped the hydrology of Mars, including the
00:07:41 --> 00:07:44 formation of the basins that may have held
00:07:44 --> 00:07:47 water. Those northern lowlands are exactly
00:07:47 --> 00:07:49 where you'd put an ancient ocean, if Mars
00:07:49 --> 00:07:52 ever had one. So whatever made the north low
00:07:52 --> 00:07:55 may also have decided where the water went.
00:07:55 --> 00:07:57 Avery: And, um, there's a nice bit of symmetry for
00:07:57 --> 00:07:58 us, isn't there?
00:07:58 --> 00:08:01 Anna: There is. We're a show made in the southern
00:08:01 --> 00:08:03 hemisphere that spends a lot of time
00:08:03 --> 00:08:05 explaining why the southern sky is the
00:08:05 --> 00:08:08 interesting one. Turns out Mars southern
00:08:08 --> 00:08:11 hemisphere is the interesting one too. It's
00:08:11 --> 00:08:13 just interesting several hundred kilometres
00:08:13 --> 00:08:13 down.
00:08:14 --> 00:08:16 Avery: Anything coming that would test this further?
00:08:17 --> 00:08:19 Anna: More of the same. The tracking data keeps
00:08:19 --> 00:08:21 accumulating as long as we keep flying
00:08:21 --> 00:08:23 orbiters. And the technique sharpens the
00:08:23 --> 00:08:25 longer the baseline gets. A second
00:08:25 --> 00:08:28 seismometer on Mars would help enormously.
00:08:28 --> 00:08:31 But there isn't one funded in flying in the
00:08:31 --> 00:08:33 meantime. This is a very good example of
00:08:33 --> 00:08:36 squeezing genuinely new physics out of data.
00:08:36 --> 00:08:39 Avery: We already had storey two and
00:08:39 --> 00:08:40 it's a stand down.
00:08:40 --> 00:08:43 Anna: Crew 13 was scheduled to launch to the
00:08:43 --> 00:08:45 International space station on September
00:08:45 --> 00:08:48 12th. It's not launching on September
00:08:48 --> 00:08:50 12th. NASA and SpaceX announced on
00:08:50 --> 00:08:53 August 29th that they'd found an oxidizer
00:08:53 --> 00:08:56 leak in the Dragon spacecraft's propulsion
00:08:56 --> 00:08:59 system during standard pre launch processing.
00:08:59 --> 00:09:01 Avery: Standard processing meaning caught on the
00:09:01 --> 00:09:03 ground doing the cheques you do?
00:09:03 --> 00:09:06 Anna: Exactly. And that's worth saying, clearly,
00:09:06 --> 00:09:09 because Leak found on crew spacecraft
00:09:09 --> 00:09:12 reads alarming in a headline. This was the
00:09:12 --> 00:09:14 process working the way it's supposed to.
00:09:14 --> 00:09:16 Teams are running additional tests and data
00:09:16 --> 00:09:19 reviews and will do any rework needed before
00:09:19 --> 00:09:21 flight. No new target date yet.
00:09:22 --> 00:09:25 Avery: Why is an oxidizer leak, specifically a, uh,
00:09:25 --> 00:09:26 stop everything item?
00:09:26 --> 00:09:28 Anna: Because of what the Dragon's propulsion
00:09:28 --> 00:09:31 system is for and what's in it. Dragon
00:09:31 --> 00:09:34 runs hypergolic propellants, a fuel and
00:09:34 --> 00:09:37 an oxidizer that ignite on contact with each
00:09:37 --> 00:09:40 other. No spark needed. Fantastically
00:09:40 --> 00:09:42 reliable, which is exactly why you use it on
00:09:42 --> 00:09:45 a crew vehicle. But the oxidizer side is
00:09:45 --> 00:09:48 aggressively corrosive and you handle it with
00:09:48 --> 00:09:50 enormous care. And that propulsion system
00:09:50 --> 00:09:53 isn't just for manoeuvring. The same broad
00:09:53 --> 00:09:56 system family is tied to the launch escape
00:09:56 --> 00:09:58 capability, the thing that pulls the capsule
00:09:58 --> 00:10:00 off a failing rocket.
00:10:00 --> 00:10:03 Avery: So the bar for signing it off is about as
00:10:03 --> 00:10:03 high as it gets.
00:10:04 --> 00:10:07 Anna: Nobody is flying this until they can explain
00:10:07 --> 00:10:09 precisely where the leak was and why it won't
00:10:09 --> 00:10:12 happen again. Who's on this Crew
00:10:12 --> 00:10:14 commander is NASA's Jessica Watkins,
00:10:15 --> 00:10:18 pilot is NASA's Luke Delany. And the two
00:10:18 --> 00:10:20 mission specialists are Joshua Kutryk from
00:10:20 --> 00:10:23 the Canadian Space Agency and Sergey
00:10:23 --> 00:10:26 Tetrietnikov from Roscosmos. It's
00:10:26 --> 00:10:28 a roughly seven month increment. A lot of
00:10:28 --> 00:10:30 station maintenance. Several spacewalks
00:10:30 --> 00:10:32 planned the usual science load
00:10:33 --> 00:10:34 Avery: and, um, they'd be walking into a station
00:10:34 --> 00:10:37 that's just had a very busy month. We talked
00:10:37 --> 00:10:40 Yesterday about Expedition 75 running
00:10:40 --> 00:10:42 four spacewalks inside four weeks,
00:10:42 --> 00:10:43 which is
00:10:43 --> 00:10:46 Anna: exactly the backlog Crew 13's own
00:10:46 --> 00:10:48 task list was built on top of.
00:10:48 --> 00:10:50 Avery: Does a delay cause knock on problems?
00:10:50 --> 00:10:53 Anna: Station handovers are a chain. Rotations
00:10:53 --> 00:10:55 overlap deliberately, so there's always
00:10:56 --> 00:10:58 experienced crew aboard and a slip at one end
00:10:58 --> 00:11:01 compresses things at the other. NASA hasn't
00:11:01 --> 00:11:04 flagged any concern beyond the launch date
00:11:04 --> 00:11:06 itself, so read that as manageable for
00:11:06 --> 00:11:07 now.
00:11:07 --> 00:11:09 Avery: When do we expect a new date?
00:11:09 --> 00:11:12 Anna: Unknown. And it depends entirely on what the
00:11:12 --> 00:11:15 inspections find, a fitting or A seal is a
00:11:15 --> 00:11:17 fix measured in days. Something in the
00:11:17 --> 00:11:20 plumbing that needs the system opened up is
00:11:20 --> 00:11:23 longer. NASA's line is that a new target will
00:11:23 --> 00:11:25 be announced once available, and we'll flag
00:11:25 --> 00:11:26 it the moment it lands.
00:11:27 --> 00:11:29 Avery: Storey three closes a loop. We opened a
00:11:29 --> 00:11:31 couple of weeks back and it's a better ending
00:11:31 --> 00:11:32 than I expected.
00:11:33 --> 00:11:34 Anna: It genuinely is.
00:11:34 --> 00:11:37 NASA's Neil Gehrels Swift Observatory is
00:11:37 --> 00:11:40 doing science again. Two of its three
00:11:40 --> 00:11:42 instruments came back online on August
00:11:42 --> 00:11:45 26, and NASA expects the third within
00:11:45 --> 00:11:45 weeks.
00:11:46 --> 00:11:48 Avery: Remind everyone how Swift got into trouble.
00:11:49 --> 00:11:51 Anna: Swift launched in 2004 to catch
00:11:51 --> 00:11:54 Gamma ray bursts, the brightest explosions in
00:11:54 --> 00:11:57 the universe, by slewing incredibly fast
00:11:57 --> 00:11:59 to point at one with within seconds of
00:11:59 --> 00:12:02 detecting it. Hence the name 22
00:12:02 --> 00:12:05 years of workhorse science. But it's in
00:12:05 --> 00:12:07 low Earth orbit, which has just enough
00:12:07 --> 00:12:10 atmosphere in it to slowly drag you down.
00:12:10 --> 00:12:12 And Swift has no propulsion at all.
00:12:13 --> 00:12:14 Avery: So it can't save itself.
00:12:14 --> 00:12:17 Anna: It can't. As the orbit decayed, NASA
00:12:17 --> 00:12:20 started shutting things off to buy time. The
00:12:20 --> 00:12:23 ultraviolet and optical telescope and the X
00:12:23 --> 00:12:26 ray telescope went dark in February. The
00:12:26 --> 00:12:28 Burst Alert telescope in April, partly for
00:12:28 --> 00:12:31 power and partly to hold an orientation that
00:12:31 --> 00:12:34 minimised drag, the space
00:12:34 --> 00:12:35 equivalent
00:12:35 --> 00:12:38 Avery: of tucking your arms in. And meanwhile,
00:12:38 --> 00:12:39 there was a rescue coming.
00:12:39 --> 00:12:42 Anna: Catalyst Space's Link spacecraft, launched
00:12:42 --> 00:12:45 in July, designed to rendezvous with Swift,
00:12:45 --> 00:12:48 grab hold and boost the orbit. The first
00:12:48 --> 00:12:51 commercial rescue of a NASA science mission.
00:12:51 --> 00:12:54 Then, on August 19, NASA called it off.
00:12:54 --> 00:12:57 Link developed problems controlling its own
00:12:57 --> 00:13:00 orientation, which, for a spacecraft whose
00:13:00 --> 00:13:02 whole job is a delicate close proximity
00:13:02 --> 00:13:04 capture, is disqualifying.
00:13:05 --> 00:13:07 Avery: So what changed to let Swift start observing
00:13:07 --> 00:13:08 again?
00:13:08 --> 00:13:11 Anna: The calculus. With no rescue coming, there's
00:13:11 --> 00:13:13 no point conserving altitude for a rendezvous
00:13:13 --> 00:13:16 that isn't going to happen. So NASA turned
00:13:16 --> 00:13:19 the telescopes back on to get every last
00:13:19 --> 00:13:20 observation out of it.
00:13:21 --> 00:13:22 Avery: How long have they got?
00:13:22 --> 00:13:25 Anna: NASA's estimate is that Swift drops below
00:13:25 --> 00:13:26 about 300 kilometres
00:13:28 --> 00:13:31 in the next one to two months. Below that,
00:13:31 --> 00:13:33 the drag makes precise pointing difficult
00:13:33 --> 00:13:36 and the telescopes stop being useful.
00:13:36 --> 00:13:37 Reentry follows.
00:13:38 --> 00:13:40 Avery: So weeks of real science left?
00:13:40 --> 00:13:43 Anna: Weeks. And given. Swift's specialty is
00:13:43 --> 00:13:45 catching things that appear without warning.
00:13:45 --> 00:13:48 Every day up there is a day it might catch
00:13:48 --> 00:13:50 something nobody else was pointed at.
00:13:50 --> 00:13:52 Avery: What happens to Link?
00:13:52 --> 00:13:54 Anna: The other decent bit of news? Catalyst isn't
00:13:54 --> 00:13:57 writing it off. They'll fly proximity
00:13:57 --> 00:14:00 operations anyway to demonstrate in orbit
00:14:00 --> 00:14:02 servicing techniques. So the mission that
00:14:02 --> 00:14:05 couldn't save Swift still generates data for
00:14:05 --> 00:14:07 the next one that tries. And there's a whole
00:14:07 --> 00:14:10 generation of productive science spacecraft
00:14:10 --> 00:14:12 in low orbit with no propulsion, all
00:14:12 --> 00:14:15 quietly losing altitude. Swift is the test
00:14:15 --> 00:14:18 case for whether we ever get good at going up
00:14:18 --> 00:14:18 after them.
00:14:19 --> 00:14:21 Avery: Last storey before the sky. And it's the most
00:14:21 --> 00:14:23 quietly audacious thing
00:14:23 --> 00:14:25 Anna: I've read in the While a nonprofit in the
00:14:25 --> 00:14:28 Seattle area called the Fermi Explora Mission
00:14:28 --> 00:14:30 announced this week that it intends to launch
00:14:30 --> 00:14:33 a, uh, spacecraft to Alpha Centauri at the
00:14:33 --> 00:14:36 end of 2029. Travel time, about
00:14:36 --> 00:14:37 80 years.
00:14:37 --> 00:14:39 Avery: That's not a typo.
00:14:39 --> 00:14:42 Anna: Not a typo. And the team's own framing is the
00:14:42 --> 00:14:45 best part. Their president, Philip Johnston,
00:14:45 --> 00:14:48 says we'll be the first to leave and the
00:14:48 --> 00:14:48 last to arrive.
00:14:49 --> 00:14:51 Avery: Meaning they fully expect to be overtaken
00:14:51 --> 00:14:52 completely.
00:14:52 --> 00:14:55 Anna: It's baked in. Somebody will build something
00:14:55 --> 00:14:57 faster in the intervening millennia and beat
00:14:57 --> 00:15:00 them there. His other line none of us will be
00:15:00 --> 00:15:02 here when this journey ends. And that is the
00:15:02 --> 00:15:03 point.
00:15:03 --> 00:15:06 Avery: So what actually flies 80 years
00:15:06 --> 00:15:08 suggests they're not waiting on exotic
00:15:08 --> 00:15:08 propulsion.
00:15:08 --> 00:15:11 Anna: Deliberately not Nothing that needs
00:15:11 --> 00:15:14 inventing. A spacecraft in the 100 to
00:15:14 --> 00:15:16 200 kilogramme range. Solar electric
00:15:16 --> 00:15:19 propulsion to proven technology. We fly today
00:15:19 --> 00:15:22 carrying at least a kilogramme of payload in
00:15:22 --> 00:15:24 a shielded 10 centimetre cube.
00:15:24 --> 00:15:26 Avery: How do you get to interstellar speed?
00:15:26 --> 00:15:29 Anna: With an ion thruster, a manoeuvre they call
00:15:29 --> 00:15:31 perihelion pumping. Instead of burning
00:15:31 --> 00:15:34 straight outward, you loop in close to the
00:15:34 --> 00:15:37 sun and thrust hard at closest approach,
00:15:37 --> 00:15:40 where you're moving fastest. That's the Obert
00:15:40 --> 00:15:43 effect. And it converts your fuel into far
00:15:43 --> 00:15:45 more speed than the same burn would out here.
00:15:46 --> 00:15:48 Repeat it and you build real Velocity.
00:15:49 --> 00:15:51 They're targeting 24.2
00:15:51 --> 00:15:54 kilometres a second at cruise, about
00:15:54 --> 00:15:57 54 miles an hour faster
00:15:57 --> 00:15:59 than New Horizons was moving at Pluto.
00:16:00 --> 00:16:02 Avery: And, um, still nowhere near enough for four
00:16:02 --> 00:16:03 and a bit late years.
00:16:04 --> 00:16:06 Anna: 4.4. That's the honest
00:16:06 --> 00:16:09 arithmetic of interstellar travel. 12
00:16:09 --> 00:16:12 years of active operations, then roughly
00:16:12 --> 00:16:15 79 and a half thousand years of
00:16:15 --> 00:16:16 coasting in the dark.
00:16:17 --> 00:16:17 Avery: Who's behind it?
00:16:18 --> 00:16:20 Anna: Donston founded it with Ezra Feldon and
00:16:20 --> 00:16:23 Adi Oltean. The three of them are behind the
00:16:23 --> 00:16:26 space computing company Star Cloud. The
00:16:26 --> 00:16:28 advisory board has real names on it. Rob
00:16:28 --> 00:16:31 Meyerson, who used to run Blue Origin, and
00:16:31 --> 00:16:34 Jeff Thornberg, formerly SpaceX's
00:16:34 --> 00:16:36 propulsion lead budgets under $15
00:16:37 --> 00:16:39 million, with one billionaire space founder
00:16:39 --> 00:16:41 verbally pledging 10 million of it.
00:16:42 --> 00:16:43 Avery: What's it carrying?
00:16:43 --> 00:16:45 Anna: A digitised Voyager golden record.
00:16:46 --> 00:16:48 Messages from children around the world and
00:16:48 --> 00:16:51 real instruments. Cosmic ray detectors among
00:16:51 --> 00:16:54 them. The 12 active years aren't nothing.
00:16:54 --> 00:16:56 You'd be measuring your way out through the
00:16:56 --> 00:16:57 heliosphere.
00:16:58 --> 00:16:59 Avery: And the name's doing Some work.
00:17:00 --> 00:17:02 Anna: The Fermi is Enrico Fermi and his
00:17:02 --> 00:17:05 paradox. If the galaxy should be full of
00:17:05 --> 00:17:07 civilizations, where is everybody?
00:17:08 --> 00:17:10 Johnston's argument is that one candidate
00:17:10 --> 00:17:13 answer is that interstellar expansion is
00:17:13 --> 00:17:15 so hard, nobody bothers to start.
00:17:16 --> 00:17:18 So you start even badly, even
00:17:18 --> 00:17:19 slowly.
00:17:19 --> 00:17:21 Avery: How is it different from breakthrough
00:17:21 --> 00:17:24 Starshot, which made a lot of noise in 2016?
00:17:24 --> 00:17:27 Anna: Starshot was the opposite bet. Laser
00:17:27 --> 00:17:30 pushed light sales. 20% of light speed
00:17:30 --> 00:17:33 arrive within a human lifetime. But needing
00:17:33 --> 00:17:36 technology that doesn't exist, it's stalled.
00:17:37 --> 00:17:39 Fermi Explorer inverts it. Use only what
00:17:39 --> 00:17:42 exists except an absurd travel time
00:17:42 --> 00:17:45 and actually launch. It'd also be the
00:17:45 --> 00:17:48 first spacecraft ever deliberately aimed at a
00:17:48 --> 00:17:51 particular star. The Voyagers are leaving,
00:17:51 --> 00:17:53 but they're not going anywhere in particular.
00:17:54 --> 00:17:57 Avery: I find this weirdly moving and I can't fully
00:17:57 --> 00:17:58 justify why.
00:17:58 --> 00:18:00 Anna: It's the honesty of it. Most space
00:18:00 --> 00:18:03 projects sell you a payoff you'll live to
00:18:03 --> 00:18:05 see. This one explicitly doesn't and
00:18:05 --> 00:18:07 asks you to fund it anyway.
00:18:08 --> 00:18:10 Avery: Right, let's get everyone sorted with today's
00:18:10 --> 00:18:12 sky watch. And September is a good month.
00:18:12 --> 00:18:15 There are five planets in play, all
00:18:15 --> 00:18:17 Anna: five naked eye ones spread across the night.
00:18:18 --> 00:18:20 Let's take them in order of when you'd see
00:18:20 --> 00:18:20 them.
00:18:20 --> 00:18:21 Avery: Start with the evening.
00:18:21 --> 00:18:24 Anna: Venus, and it's unmissable.
00:18:24 --> 00:18:27 Low in the west to west southwest after
00:18:27 --> 00:18:30 sunset, about 14 degrees up an hour after
00:18:30 --> 00:18:32 the sun goes down. For Sydney sunsets
00:18:32 --> 00:18:35 around 5.34pm AEST
00:18:35 --> 00:18:37 tonight, so you're looking from a quarter
00:18:37 --> 00:18:40 past six. Northern listeners get a similar
00:18:40 --> 00:18:43 window after their own sunset. The key
00:18:43 --> 00:18:46 either way is a genuinely flat western
00:18:46 --> 00:18:49 horizon because Venus is not high.
00:18:49 --> 00:18:51 Avery: It was next to Spica last night.
00:18:52 --> 00:18:54 Anna: That conjunction peaked yesterday and they're
00:18:54 --> 00:18:57 separating now, but Spica is still right
00:18:57 --> 00:18:59 there. Worth a look through binoculars while
00:18:59 --> 00:19:02 they're close. Venus builds to maximum
00:19:02 --> 00:19:04 brilliance on the 18th, so it only
00:19:04 --> 00:19:07 improves mark the 14th too, when a
00:19:07 --> 00:19:09 thin crescent moon sits beside it.
00:19:10 --> 00:19:11 Avery: Then Saturn.
00:19:11 --> 00:19:13 Anna: Saturn's the one to actually point a
00:19:13 --> 00:19:16 telescope at this month. Up for most of the
00:19:16 --> 00:19:19 night. Magnitude 0.4
00:19:19 --> 00:19:22 and the rings are tilted just 8 degrees from
00:19:22 --> 00:19:24 edge on the narrowest in about a dozen
00:19:24 --> 00:19:27 years. That's a genuinely unusual view
00:19:27 --> 00:19:30 and it won't look like this again for a long
00:19:30 --> 00:19:30 time.
00:19:31 --> 00:19:32 Avery: And, um, there's a hemisphere difference
00:19:32 --> 00:19:33 here,
00:19:33 --> 00:19:36 Anna: a big one in our favour for once. From
00:19:36 --> 00:19:38 Sydney or Auckland or Cape Town, Saturn
00:19:38 --> 00:19:41 climbs high overhead. Less atmosphere to look
00:19:41 --> 00:19:44 through, so a steadier, sharper view from the
00:19:44 --> 00:19:47 northern US or the uk. It stays comparatively
00:19:47 --> 00:19:49 low and you'll be fighting turbulence.
00:19:49 --> 00:19:52 Northern listeners wait for it to get as high
00:19:52 --> 00:19:54 as it gets. And be patient with the seeing
00:19:54 --> 00:19:57 morning sky. Mars rises around
00:19:57 --> 00:20:00 1:40am that distinctive amber
00:20:00 --> 00:20:02 colour slowly brightening as Earth catches up
00:20:02 --> 00:20:05 to it. Then Jupiter up in the east
00:20:05 --> 00:20:08 northeast around 10 to 4 and easier to
00:20:08 --> 00:20:10 catch before dawn every week.
00:20:10 --> 00:20:12 Avery: And there's a Jupiter event for our North
00:20:12 --> 00:20:15 American listeners, specifically a good one.
00:20:15 --> 00:20:18 Anna: On September 8, the moon passes
00:20:18 --> 00:20:20 directly in front of Jupiter, an actual
00:20:20 --> 00:20:23 occultation visible from much of North
00:20:23 --> 00:20:26 America. Jupiter winks out behind the
00:20:26 --> 00:20:28 lunar limb and reappears on the other side.
00:20:29 --> 00:20:31 Small telescope makes it spectacular.
00:20:31 --> 00:20:34 Binoculars will show it. Not for us down
00:20:34 --> 00:20:36 south. So northern listeners, that one's
00:20:36 --> 00:20:38 yours. Put it in the calendar.
00:20:38 --> 00:20:40 Avery: And um, the fifth planet Mercury.
00:20:40 --> 00:20:43 Anna: But you'll wait for it final week of
00:20:43 --> 00:20:45 September. Low in the west southwest in
00:20:45 --> 00:20:48 evening twilight, magnitude minus
00:20:48 --> 00:20:51 0.1 on the 25th. It sits
00:20:51 --> 00:20:54 about a degree above Spica, which is a handy
00:20:54 --> 00:20:54 way to find it.
00:20:55 --> 00:20:56 Avery: What's the Moon doing tonight?
00:20:56 --> 00:20:59 Anna: Waning gibbous, past full heading for
00:20:59 --> 00:21:02 last quarter on the fourth. It's rising later
00:21:02 --> 00:21:05 each night, so the early evening is getting
00:21:05 --> 00:21:07 properly dark again. Good news for anything
00:21:07 --> 00:21:08 sane.
00:21:08 --> 00:21:09 Avery: Anything else for the diary?
00:21:10 --> 00:21:12 Anna: The 19th is international. Observe the moon
00:21:12 --> 00:21:15 night. The 22nd is the equinox.
00:21:15 --> 00:21:17 Spring for us, autumn for our northern
00:21:17 --> 00:21:20 listeners. And around the 26th the full
00:21:20 --> 00:21:23 moon rises near Saturn with Neptune close
00:21:23 --> 00:21:26 by. If you've got binoculars and patience, if
00:21:26 --> 00:21:29 you want the Milky Way itself. Mid month is
00:21:29 --> 00:21:32 the window, roughly the 14th to the 20th
00:21:32 --> 00:21:34 when the moon's out of the evening sky. The
00:21:34 --> 00:21:37 core and Harry's in Scorpius. The
00:21:37 --> 00:21:40 teapot in Sagittarius sits high
00:21:40 --> 00:21:42 overhead. For us northern listeners get the
00:21:42 --> 00:21:45 same region but low toward the south. So
00:21:45 --> 00:21:47 you'll want a dark site and a clear southern
00:21:47 --> 00:21:48 horizon.
00:21:48 --> 00:21:51 Avery: One standing reminder before we go, the
00:21:51 --> 00:21:53 Anna: one we never skip. If you're pointing
00:21:53 --> 00:21:56 anything at or near the sun, whether
00:21:56 --> 00:21:58 that's sunspots, a ah, transit or just
00:21:58 --> 00:22:01 chasing Venus a bit too close to sunset.
00:22:01 --> 00:22:04 Any filter you use must be Certified to
00:22:04 --> 00:22:05 the ISO
00:22:05 --> 00:22:08 123122.
00:22:08 --> 00:22:11 Standard sunglasses are not solar
00:22:11 --> 00:22:13 filters. Welding glass off the shelf is not
00:22:13 --> 00:22:16 a solar filter. Improvised filters
00:22:16 --> 00:22:18 cause permanent damage in seconds.
00:22:19 --> 00:22:20 Certified or don't look.
00:22:21 --> 00:22:23 Avery: Never gets old, never should.
00:22:23 --> 00:22:25 And that brings us to the end of today's
00:22:25 --> 00:22:28 show. Molten anomaly under Mars southern
00:22:28 --> 00:22:30 hemisphere. That may finally explain the
00:22:30 --> 00:22:33 crustal dichotomy. Crew 13 standing
00:22:33 --> 00:22:35 down over an oxidizer leak in Dragon.
00:22:36 --> 00:22:38 Swift back doing science in a race against
00:22:38 --> 00:22:41 its own orbit. An 80 year
00:22:41 --> 00:22:44 mission to Alpha Centauri and five planets
00:22:44 --> 00:22:45 to hunt down this month.
00:22:46 --> 00:22:48 Anna: If you enjoyed today's episode, the best
00:22:48 --> 00:22:50 thing you can do for us is leave a rating or
00:22:50 --> 00:22:52 review wherever you're listening and share it
00:22:52 --> 00:22:55 with a fellow space nerd. It really does help
00:22:55 --> 00:22:57 us out and makes a difference. Plus, you get
00:22:57 --> 00:22:59 featured on our new website, where you can
00:22:59 --> 00:23:02 also find full show notes, sources and
00:23:02 --> 00:23:05 links for every storey we covered today. Just
00:23:05 --> 00:23:07 point your browser to astronomydaily
00:23:07 --> 00:23:10 IO cheque out our new blog there too.
00:23:10 --> 00:23:12 Avery: We'll be back tomorrow with more space and
00:23:12 --> 00:23:15 astronomy news. Until then, keep looking up.
00:23:15 --> 00:23:17 Anna: See you next time. Clear skies, everyone.