A Round Trip to Phobos Underway

0:00 Anna: Hi everyone. Welcome back. It is a Tuesday morning in Sydney, a um, Monday afternoon in New York and somewhere off the southern tip of Japan a rocket has just tried to carry a spacecraft towards the moons of Mars. Avery: And uh, this one is planning to come back with a handful of Phobos in its pocket and a landing in South Australia pencilled in for 2031. Anna: Welcome to Astronomy AstroDailyPod. I'm Anna. Avery: And I'm Avery. Today, Japan's Martian moons exploration mission mmx and the question it was built to answer then more than half of the biggest telescope mirror ever made has now reached Chile.

0:42 A year old preprint finally becomes a paper with an awkward message for anyone modelling the dawn of the universe. And a musical looking radial source hiding behind the Milky Way turns out to be a uh, cosmic phoenix. Anna: Plus Hera's breaking burn, the Orionid meteors and the last week of Venus in the evening sky. Let's go. Avery: Ready when you are. Anna: Okay. Mars has two moons and nobody's quite sure where either of them came from. Phobos is about 27 kilometres across at its longest, lumpy, dark and so close to Mars that it goes around three times a day.

1:22 Deimos is smaller and further out. They look a lot like asteroids. That is half the puzzle. Avery: They were found in 1877 by Asaph hall at the U.S. naval Observatory and named for the attendance of the God of Phobos. Fear and Deimos dread. Phobos orbits only about 6,000 kilometres above the Martian surface, closer than any other moon to its planet in the solar system. And it's slowly spiralling inwards. In something like 30 to 50 million years, it's expected to be torn apart or crash into Mars.

1:56 Anna: So it's a moon with a deadline. It's also scarred by a crater called Stickney, about nine kilometres wide on a body only 27 kilometres long. Whatever made that came very close to breaking Phobos apart. Avery: And the other half of the puzzle is that their orbits don't look like asteroid orbits. Captured asteroids should end up on tilted stretched paths. Phobos and Deimos sit almost in Mars equatorial plane on nearly circular orbits. That's what you'd expect if they formed from a disc of debris around Mars itself thrown up by a giant impact.

2:36 Two good stories. And um, they predict different rocks, which Anna: is exactly why you go and get some. That is the job of mmx, the Martian Moons exploration mission led by jaxa, the Japan Aerospace Exploration Agency, with NASA, the French Space Agency sines, the German Aerospace Centre DLR and the European Space Agency as Partners. Avery: So what happened? Anna: It went. JAXA has confirmed that the H3 lifted off and that MMX has separated from the rocket and is on its way. The spacecraft weighed about 4 1/2 tons at uh launch, which tells you how much fuel a round trip to Mars takes.

3:20 Avery: Worth saying, because H3 has not had an easy life. Its very first flight was lost in 2023. A clean launch carrying a flagship planetary mission matters for the vehicle as much as for the spacecraft. Anna: The cruise to Mars takes about a year. ESA's timeline has MMX entering orbit around Mars in August 2027 and moving onto what's called a quasi satellite orbit around Phobos from September 2027. Phobos is too small to orbit in the ordinary way, so the spacecraft flies a loop around it while both go round Mars together.

3:58 Avery: Then comes a long, careful survey. MMX carries 11 science instruments in all, seven on the main spacecraft and four on a small rover. One of those seven is NASA's contribution, a gamma ray and neutron spectrometer called Megan, which reads the elements in Phobos surface from orbit. That's how the team chooses where to land. Anna: The rover is called Edifics, built by CNES and DLR. It weighs about 25 kilogrammes on earth. On Phobos, ESA says it will weigh about 15 grammes. 15 grammes? You could knock it off the surface with a sneeze, which is why the rover's first job is to find out how Phobos surface actually behaves before the main spacecraft commits to touching it.

4:44 Avery: Edifics is due to be released in early 2029. The landing and sampling follow in 2030, and the return module heads home with at least 10 grammes of Phobos. MMX carries two separate sampling devices, so it isn't relying on a single grab. It will also study Deimos from a distance and fly past it and Mars on the way out. Anna: For scale, Hayabusa2 brought back about five and a half grammes from asteroid Ryugu, and that tiny amount has fed hundreds of studies. GAXA has done sample return twice before.

5:17 This is the first time anyone has tried it in the Mars system, and it sits alongside Europe's plans, too. ESA's Mars Express, now confirmed to operate until at least 2029, may support MMX's observations. And the ExoMars Rothland Franklin rover is meant to complement it by drilling beneath the Martian surface. 10 grammes sounds tiny, and it's worth explaining why the people who built this are so excited about it. A captured asteroid and a chunk of Mars thrown into orbit would carry very different chemical fingerprints in their minerals, in their water, in the ratios of isotopes that labs on Earth can measure to astonishing precision.

5:57 Orbiters can hint at those differences. A sample settles them. Avery: And there's a bonus. Phobos has spent billions of years sitting right next to Mars collecting material blasted off the Martian surface by impacts. So a, uh, Phobos sample may well contain little grains of Mars itself, delivered without anyone having to land on Mars and fly back up. Anna: This also connects to a story we covered back in episode 181, the study suggesting Deimos may have formed from a single impact on Mars. MMX is the test.

6:31 If the moons are Martian debris, the Avery: rocks will say so here's the southern hemisphere bit, and, um, it's a good one. When MMX comes home in 2031, the capsule is expected to land in South Australia. The Australian Space Agency and JAXA formalise their cooperation on the mission in 2023. Anna: And this is a path well worn. JAXA's Hayabusa capsule came down at Woomera in 2010 with grains from asteroid Itokawa. And Hayabusa2's capsule landed there in December 2020 with material from Ryugu. One honest caveat.

7:08 The agency's own page says South Australia, rather than naming a site for mmx. So we're not going to name one for them. But if a third Japanese sample capsule streaks across an outback night sky in 2031, nobody will be surprised. Avery: ESA's project scientist Elliot Sefton Nash calls returned samples the gift that keeps on giving. The Apollo rocks are still producing papers more than 50 years on. If this works, Phobos will be on lab benches long after everyone who built MMX has retired. Anna: An ambiguous project indeed.

7:44 And here's wishing them every success. Avery: Staying in the south. The The European Southern Observatory says more than half of the main mirror of its Extremely Large Telescope has now arrived in Chile. Anna: That mirror is 39 metres across. You can't cast a single piece of glass that size, so it's built from 798 hexagonal segments that act together as one surface. And because the reflective coating wears out, ESO has made 133 spares as well, 931 segments in total, so that once the telescope is running, two segments a day can be swapped out for recoding without ever leaving a hole.

8:23 Avery: Two a day, every day for the life of the telescope. That's a job description. And these aren't dinner plates. Each hexagon is roughly one and a half metres across and only a few centimetres thick. And ESO's spec is that the surface is smooth to better than 10nm, like less than a thousandth of the width of a human hair. Anna: Nearly 500 segments are now sitting at the ELT technical facility at Paranal. The journey is a genuinely European one. Blanks of a glass ceramic called Zerodur, cast by Schott in Germany, polished near Poitiers in France by Saffron Riosque, mounted on supports designed and made by two Dutch companies, fitted with sensors and actuators from France and Germany, and then shipped 10,000 kilometres to the Atacama by Danish logistics firm DSV.

9:19 Avery: And the pace has changed. The first segments only reached chile in early 2024. Safran Riosque is now finishing a segment a day, and the very last one has entered production. ESO expects all of them to be in Chile within months now, one number Anna: to be careful with. ESO says the ELT project as a whole is more than 75% complete and that the first observations with scientific instruments are planned for late 2030. If you've seen 2028, quoted for the ELT's first light in older material, those aren't quite the same milestone.

9:56 But it's fair to say the science dates it's later than many people had in their heads. Avery: And the science, when it comes, is the reason to wait. The atmospheres of rocky planets around other stars, the first galaxies, and even whether the constants of physics have drifted over cosmic time. It sits on cerro armasones, about 20 kilometres from the Very Large Telescope at Parnal, under some of the darkest skies on Earth. And Australia, as an ESO strategic partner, has a seat at that table. Anna: Now a story about the first billion years of the universe told using galaxies in our own backyard.

10:37 Avery: Quick background after the Big Bang cooled, the universe filled with neutral hydrogen gas, which soaks up the high energy ultraviolet light that can ionise it. Astronomers call that light the Lyman continuum. At some point, the first stars and galaxies produce enough of it to strip the electrons back off almost all that hydrogen. That's reionization. The big open question is which galaxies did the work and how the light got out? Anna: Because getting out is the hard part. A young galaxy is wrapped in its own gas.

11:11 For years, a lot of simulations have assumed the escape route is blasted open by supernovae. Massive stars explode, drive a wind, clear the gas and the ultraviolet light pours out. Avery: A paper published in Nature Astronomy last week suggests it may be close to the other way round. Cody Carr and Ren Yitzen of Zhejiang University and 26 co authors used the Hubble Space Telescope to look at six nearly identical compact star forming galaxies whose light left them roughly 3 to 4 billion years ago.

11:45 Same chemistry, same size, same star formation rate. The main thing that differs is the age of their latest burst of stars. Anna: Why nearby galaxies? Because you can't measure this directly. In the early universe, any ionising light escaping a galaxy at that time gets soaked up by neutral gas between the galaxies long before it reaches us. So astronomers use local lookalikes from the low redshift Lyman Continuum Survey, where Hubble's Cosmic Origins Spectrograph can catch the escaping ultraviolet itself.

12:20 Avery: And the pattern is striking. The youngest burst, at a mean stellar age of about 2.7 million years, leaks the most. About 21% of its ionising light escapes and its wind is slow, around 135 kilometres a second. The oldest bursts a little past 5 million years, leak almost nothing under half a percent. And their winds are running at 600 kilometres a second or more. Anna: That age matters because the most massive stars start going supernova at around 3 million years. So the window opens early, while the light is being pushed out by radiation and stellar winds.

12:59 And the supernovae, the thing many models were counting on to open the door, load the wind with neutral gas and close it. Avery: If you were listening in episode 199, when Andromeda's um, super bubbles turned out to be enough to keep a whole galaxy churning, or episode 194 and feedback that builds as well as breaks, this is another face of the same idea. Feedback is not one switch. Anna: Timing matters now, the honest bits. It's six galaxies. The stellar ages carry large uncertainties and the authors say so the hottest phase of the wind isn't measured.

13:38 And these are nearby stand ins, not reionization era galaxies themselves. Also a disclosure from us. The preprint first appeared in October last year, so this is published this month rather than brand new. But the implication is clear enough to state simulations that only let the light out after the supernovae may need to let it out earlier. Avery: Last story before the quick hits. A radial source that looks like a, uh, treble clef. Anna: It goes by VLSS J03 18 9.57.55, which is why everyone calls it the treble clef.

14:18 It sits almost exactly behind the plane of the Milky Way in what astronomers call the zone of avoidance, where our own galaxy's dust and gas hide most of the universe behind it. It's been known for years, and at One point was thought to be a pulsar. Avery: A team led by Andrea Botellon UM of Italy's National Institute for Astrophysics combined X rays from NASA's Chandra and the Erosita survey with radio maps from the LOFAR network and India's upgraded GMRT plus infrared from the UK Infrared telescope.

14:51 They found it sits in a massive galaxy cluster. In fact two clusters that collided a few hundred million years ago and are now moving apart. Anna: And the radio source itself is what's called a radio phoenix. Long ago, the supermassive black hole at the heart of the cluster blew out a cloud of fast particles and magnetic fields that glowed in radio, then faded. Then the cluster collision squeezed the old cloud and lit it back up. Avery: The giveaway is the colour. In radio terms, its brightness drops off incredibly steeply with frequency.

15:29 The paper puts the spectral index above 4 between 400 and 650 MHz, which is extreme. That's the signature of old electrons that have lost most of their energy. The team estimates the filament electrons are around 190 to 200 million years old. Anna: The cluster gas around it is hot, around 6 kiloelectron volts in X ray terms, which is about 70 million degrees. And there's a nice detail in the author list. Rashid Sunyayev of the Sunyayev Zeldovich effect and Eugene Churasov are both on it. These are people who have spent careers reading hot cluster gas.

16:11 Avery: As for the shape, NASA is careful to say the resemblance to a treble clef is pareidolia. Our brains finding a pattern. The real shape is probably sculpted by gas sloshing around inside the cluster. Anna: The thing is roughly 760 kiloparsecs across, about two and a half million light years in a cluster weighing around half a million billion suns. Seen as it was about 1 1/2 Avery: billion years ago, the preprint dates from July. So this is a, uh, NASA release this month about a paper that's been circulating for three months and no Australian telescope in this one.

16:53 It's a northern sky object, but steep spectrum, low frequency radio sources are exactly the kind of thing Ska Lo in Western Australia is being built to find. So Expect more Phoenixes. Anna: Three quick ones first. HERA ESA's asteroid mission completed its first braking manoeuvre on Thursday. Three thrusters firing together for 93 minutes. ESA confirmed on Friday that it performed within the required parameters. The follow up burn is scheduled for this Thursday, 22nd October, and arrival at the Didymos asteroid system is due In November, HERA is going to measure what NASA's DART impact did to the little moonlit dimorphos in 2022, the first real test of whether we could nudge a, uh, dangerous asteroid.

17:41 Avery: Second, the satellite that rode up with Flex In September, Copernicus Sentinel 3C has sent back its first images. And the Caribbean, Italy from southern Germany to Sicily and the Canadian Arctic, plus sea surface heights and the height of the Greenland ice sheet from its radar altimeter. ESA says commissioning has about five months Anna: to run and third, Swift DASA has still not published a re entry date for the observatory after the failed Boost mission and recent press coverage points to early November.

18:14 That thread began with your questions through the contact form, so we'll bring you NASA's confirmation when it comes time to look up. Avery: This week belongs to the Moon, the Orionids and a planet saying goodbye. Anna: The Moon reached first quarter early on Monday Sydney time, and it's growing towards full on 26-10-0411 Universal Time, which is 3:11 Monday afternoon in Sydney, just after midnight on the 26th in New York and 9:11 on the evening of the 25th in Los Angeles. In the north, that's the Hunter's Moon, and like the harvest Moon we talked about in episode 199, its short gap between successive moonrises is a northern effect from the south.

19:01 The anti Harvest Moon rule still applies, Avery: which matters because the Orionid, uh, meteor shower peaks on the nights of the 21st and 22nd. The Orionids are debris from Hallie's Comet, the same dust that gives us the Eta Aquarids in May, and they hit our atmosphere at around 66 kilometres a second. So they're quick and the brightest can leave glowing trails that hang for a second or two. And the moon is about 80% lit, so the evening is no good. The trick is to go late. Anna: We ran the numbers for the morning of Thursday the 22nd.

19:37 The moon sets at 3.38am in Sydney, 322 in Los Angeles, 312 in New York and 249 in London. That gives you a dark window of about 90 minutes in Sydney and roughly three hours in the north before dawn starts to brighten. Avery: And here the north has the better of it. By nautical dawn, the radiant up near Orion's raised club stands about 68 degrees high from Los Angeles, 62 from New York and 52 from London against about 40 degrees from Sydney. The higher the radiant, the more meteors you see. Expect modest rates at best, Perhaps up to 20 an hour under ideal dark skies and fewer from town.

20:21 Lie back, look about halfway up and give your eyes 20 minutes. Anna: The south gets the evening Planet Mercury had its best evening showing of the season around the 12th of October, and it's still holding on at the end of civil twilight on Wednesday the 21st. It's about 17 degrees up from Sydney in the west, setting just after 9 from Los Angeles it's 4 degrees up from New York 2 and from London it has already set. Southern listeners, this one's yours. Look low in the west about half an hour after sunset and only bring out binoculars once the sun is completely down.

21:03 Avery: Venus meanwhile, is leaving. It reaches inferior conjunction passing between us and the sun around the 24th of October and drops out of sight. It'll reappear in the morning sky in November. If you've been enjoying it in the west since September, this is the goodbye week. Anna: Saturn is well placed in the evening just past opposition and the waxing moon passes about 6 degrees from it around the 24th, a good pairing for both hemispheres and for early risers. Avery: Mars and Jupiter keep closing in the pre dawn sky about 11 degrees apart on the 19th, eight by the 26th on their way to a close pass in mid November, again a northern treat at nautical dawn on Tuesday, Mars is 61 degrees up from Los Angeles and 58 from New York against 24 from Sydney with Jupiter not far below.

21:55 Anna: And the safety line? As always, never look at the sun directly or through binoculars or a telescope without certified solar filters meeting the ISO 12322 standard. Ordinary sunglasses are not safe for solar viewing. Avery: So north the Orionids and the morning planets South Mercury and the higher evening Moon. Both of you Saturn. Some weeks it runs the other way. Anna: That's Astronomy AstroDailyPod for today. To recap, MMX um and its round trip to Phobos with a capsule bound for South Australia, more than half of the ELT's giant mirror now in Chile, Supernovae closing the window on early starlight and the treble clef rising from the radio dead.

22:42 Avery: Show notes, sources and all our episodes are at astronomydaily IO and you can find us on social astrodaily Pod if you've got a question about anything we covered the contact form on the website comes straight to the team. That's how the Swift story started. Anna: We'll keep a close eye on MMX and on Harrah's second breaking burn on Thursday. And if you do get up for the Orionids, tell us what you saw and where you saw it from north or south? We'd love to compare until next time. Avery: I'm Avery.

23:13 Anna: And I'm Anna. Clear skies.