Astronomy Cast

Last week we talked about samples from other worlds delivered to Earth by meteorites. But sometimes you’ve gotta do the job yourself. Visit the far off place and bring the samples home. And today we’re gonna talk about China’s Chang’e sample return program. How they’ve delivered rocks from different parts of the Moon, and how this sets the stage for their upcoming human lunar missions. 

Show Notes

• Chang’e Program Overview
• Chang’e 6 Mission Details
• Mission Accomplishment
• Mission Significance
• Chang’e 5 Mission Findings
• Chang’e 5 Mission Outcome
• Lunar Exploration Challenges
• Lunar Research Focus
• Moon Formation Theories
• International Lunar Collaboration
• Mission Objective
• Mission Timeline
• Mission Details
• Mars Sample Return Mission
• Mars Human Mission
• Artemis Mission Concerns

Transcript

Fraser Cain: 

AstronomyCast, Episode 791, Chang'e Sample Return. Welcome to AstronomyCast, our weekly facts-based journey through the cosmos, where we help you understand not only what we know, but how we know what we know. I'm Fraser Cain, I'm the publisher of Universe Today.

With me, as always, is Dr. Pamela Gay, a Senior Scientist for the Planetary Science Institute, and the Director of CosmoQuest. Hey, Pamela, how are you doing?

Dr. Pamela Gay: 

I am doing well. How are you doing?

Fraser Cain: 

Good. I am doing well as well. We are both enjoying the spring and getting out there with our saws and our clippers and our lawnmowers and starting to process nature, bring it back into the fold.

And yeah, it's crazy. Our mason bees just came out today. We've got a house wren that is sitting on a birdhouse that I made that is just calling and calling for a mate.

We've got swallows that have all showed up and are examining all of the swallow boxes that I built. We saw an alligator lizard yesterday, which is a highlight. It's our native lizard here on Baker Island.

Dr. Pamela Gay: 

I had no idea they went that far north.

Fraser Cain: 

Yeah, we have salamanders. So my wife found a salamander climbing out of our thyme shrubs, which was awesome. And she delivered it out into the forest.

It's just, you know, deer, I'm ready for the bears. It always just, it's always surprising. Like I've even written all this stuff down in my calendar that I talk about and yet still they show up and you're like, finally, I never knew that this would return.

And here we are, spring is returning and I just love it so much.

Dr. Pamela Gay: 

That is absolutely amazing. The thing that has not returned is my video camera functionality. So it was working and then everything said, no, I shall die now.

So those of you watching this on YouTube, I have disappeared. And we're going to continue to talk while I continue to work on this and we will go to break and I will finish fixing it when we get a break.

Fraser Cain: 

I don't look at you when we record anyway.

Dr. Pamela Gay: 

No, I know.

Fraser Cain: 

Last week, we talked about samples from other worlds delivered to earth by meteorites, but sometimes you've got to do the job yourself, visit the far off place and bring the samples home. And today we're going to talk about China's Chang'e Sample Return Program, how they've delivered rocks from different parts of the moon and how this sets the stage for their upcoming human lunar missions. All right.

So first, I think we need to talk about the pronunciation of Chang'e, Chang'e, so Chang'e. So the uh part, the last part is, and this is my instinct is because, you know, I've been learning Mandarin. And so when you are hungry, you are uh-la, so if I say I am hungry, I say wa-uh-la.

So and it's that same uh, and so it's that sort of E by itself.

Dr. Pamela Gay: 

But the name has nothing to do with hunger. Hunger.

Fraser Cain: 

No, no, no, no. So no, no, no.

Dr. Pamela Gay: 

Just to be clear.

Fraser Cain: 

Chang'e, Chang'e is, is the moon goddess.

Dr. Pamela Gay: 

Yes.

Fraser Cain: 

And so uh, that's why the whole, the whole lunar exploration program is named after the moon goddess. So uh, now we're going to sort of end on the actual sample return missions and then talk a bit about what's coming next, but let's sort of start at the beginning of the, of the Chang'e program.

Dr. Pamela Gay: 

So this is the Chinese program to uh, go to the moon, explore very completely. They've been doing slow and steady wins the race. I think it's the best way to describe their mission profile.

This started in the early 20 teens, uh, they have systematically orbited it with two different missions at successfully higher resolution. They have done landings, uh, they have done communication satellites, uh, Chang'e 5 was nearside sample return, Chang'e 6 was the, the triumvirate of awesome. It was a landing in South Aitken Basin in Apollo crater, uh, which is one of the lowest sites on the moon.

So like, holy heck, how did you do that? Um, then they, they, uh, also landed on far side as part of that and, um, they had a communication satellite, so it worked. And then the third amazingness is they then brought back nearly two kilograms of sample, um, including they drilled.

So they were able to do like things that we dreamed of doing with the Viper Rover. They have done it and they have brought the stuff back and they even took a stealth Rover that they didn't announce ahead of time and people realized was there from photos of the mission. Um, so yeah, for selfies, yeah, it's what they do.

They take selfies. It's excellent.

Fraser Cain: 

Yeah. I mean, whoever is running the, um, the promotional arm of the, of the missions of the lunar exploration missions from China has, is on the ball and they did this for Mars too. So, so when they had their, um, their Tianwen mission go to Mars, they had a little selfie, free flying selfie camera that detached from the mission and took a picture of it.

And you know, we are always talking about how, like, obviously there are no pictures of the spacecraft in orbit because you haven't sent another spacecraft to take a picture of your spacecraft. That's ridiculous. Yeah.

Dr. Pamela Gay: 

They do that.

Fraser Cain: 

Unless you're the Chinese and you send a separate spaceship with your spaceship so you can take a picture. And they, so they do this. And so you've got this great, this great picture of the Chang'e, um, on the surface of the moon taken by this, this little, uh, this little Rover that they had, they had attached.

But, but, I mean, you just, you went through six missions there very, very quickly.

Dr. Pamela Gay: 

So, so that was, that was the overview.

Fraser Cain: 

Um, but let's, let's focus on their first sample return mission.

Dr. Pamela Gay: 

Okay. So that, that's Chang'e 5 and this, this was a mission that landed like we did basically on the near side of the moon, uh, northern hemisphere. And, uh, it brought back, uh, 1.7 kilograms of lunar soil. And then what they did with the spacecraft is kind of almost more exciting to me than the lunar sample. But this is an episode on the lunar sample. So I should go into that.

Fraser Cain: 

No, no, no. But I'm like, no. Tell us the thing that's more exciting.

Dr. Pamela Gay: 

Go on. So, so they do something that we don't generally do with our earth moon system spacecraft, which is they, they took the spacecraft, they then stored it out at L2 and continue doing exploring. It wasn't a matter of just going, grabbing a sample and then ditching whatever they didn't need any further.

They're like, no, we're going to go over here now. We're going to do more stuff now. And I just kind of love that for them.

Fraser Cain: 

Yeah. Yeah. So the, the, the service module, they flew it out to the earth moon L2 Lagrange point, not to be confused with the earth sun L2 Lagrange point where James Webb and so such are.

But, um, and you know, these require a little bit of fuel to maintain your position. And so the spacecraft has gone out there and then we'll be sort of testing maneuvers for future lunar missions. And so trying to just understand how to move in this Lagrange point area.

Dr. Pamela Gay: 

And they've also been testing communications. They built a neat, uh, they're, they're using a very long baseline interferometry tests as, as part of what they're doing. Uh, so, so they have three ground based stations and now they're sticking things out there to continue running their tests.

Fraser Cain: 

Yeah. They, they put a, uh, we'll talk about this for the, for the, the sixth mission, but they, they put, they put a, um, a relay satellite on the far side of the moon because obviously you can't communicate with the far side of the moon from the surface of the earth. And so, uh, again, this is, this is all going to lead into the conversation about what the future of a, of a Chinese, uh, human mission is going to look like, because a lot of this is the same kind of, of technology.

Okay. So, uh, so they, and so what, what went to the surface of the moon?

Dr. Pamela Gay: 

I mean, they, they had a, a lander and a module on Chang'e-5, um, oh, it's, it's mainstream media has completely ruined me for pronouncing this, but I'm going to try and get it right.

Fraser Cain: 

Um, well the, the, the, the first part is just like, like you're saying like kind of shung and so think about it like cheese, Chung, cheese, Chung, yeah, Chung-ge, Chung-ge.

Dr. Pamela Gay: 

All right. So, so they had a, a orbiter, they detached from the orbiter, they had a lander and the sender module, um, and they left the lander behind, which is kind of what you do with a lander. And, uh, then they flung the sample skyward, re-docked, came, and they did a whole lot of transferring of the sample back and forth between things, which kind of surprised me.

They didn't do the, we scoop it up and then we dropped what we scooped it up into, which is kind of what we saw with OSIRIS-REx. Um, so they transferred things around and then they dropped it on the Mongolian desert as they do.

Fraser Cain: 

Right. Yeah. Um, and there's great pictures of them retrieving the sample capsule from the desert.

And what did they discover from, from bringing these samples home? Apart from we can return samples from the moon, that's what we've discovered.

Dr. Pamela Gay: 

They did find, uh, one configuration of titanium oxide that was different from minerals previously found. So they added a new mineral to the list of lunar minerals, which is always exciting. Um, they, as we have been continuously doing, they, uh, were looking to see what is the age dating of the sample.

There was nothing exciting with this side compared to the other side, which we're gonna get to. Um, but it was just like standard. Everything goes along, crater dating matches lunar sample.

Everything is happy. We found potassium. It was the creep elements.

They discovered creep elements as expected.

Fraser Cain: 

Right. Creepy. So creep, K potassium, uh, rare earth, the R E and then, uh, wait, phosphorus, right?

Yeah. I forget which one is which.

Dr. Pamela Gay: 

So there's, there's potassium and there's phosphorus both in there. Um, yeah, it's the standard set of elements. Nothing on the near side was a surprise and that's good.

That means their science matches the USSR science matches the U S science. As you would expect for the Northern hemisphere near side of the moon.

Fraser Cain: 

I mean, the biggest thing that they learned was that the volcanism lasted longer on the moon. You're talking about the creep, the such K R E E P, um, but this mixture of, of elements and this was an indication of just the volcanism on the surface of, of the moon lasting longer. So there had been volcanism more recently on the surface of the moon than, than people had originally believed.

Dr. Pamela Gay: 

Now, wasn't that a China six though?

Fraser Cain: 

That was five.

Dr. Pamela Gay: 

Okay. So they got it both from six. Yeah.

Fraser Cain: 

Yeah.

Dr. Pamela Gay: 

Both missions.

Fraser Cain: 

Yeah. Six. I mean, six really helped us understand, um, more about why the near side and the far side are, are so different.

So five was this sort of technical demonstration that China can drop a probe down onto the surface of the moon, retrieve samples, load them up, take them to space.

Dr. Pamela Gay: 

And it wasn't any dropping. It was a precision landing.

Fraser Cain: 

Yeah. Precision precision land on the surface of the moon, pick up samples, bring them to space, return them safely to the surface of the planet to put them in the hands of, of scientists. But China six was much more ambitious.

Dr. Pamela Gay: 

Just, I, I can't stress enough how impressed I am with their landing site. So they landed in the Apollo crater, which is one of the deepest places on the lunar surface. It's in the Southern hemisphere on the far side.

So they weren't flying completely blind as we would have been because they put a communication satellite there. They were, they were smart that way. Um, but like we're seeing OIG reports coming out, expressing concern about landing anywhere on the South pole with our planned landers.

We've been watching the CLPS missions, practice gymnastics, except for you, Firefly Aerospace, you did good.

Fraser Cain: 

Yeah. The rest of them fell over, crashed. Yeah.

Yeah. There's a lot of, of man, how many? Many.

Many. Yeah. There was an Indian failure.

There was two Japanese failures, three Japanese failures. And then like two NASA failures, three NASA failure. Yeah.

So it was like the moon, the, the galactic ghoul. Yeah. It eats things.

The great galactic ghoul has moved homes from Mars to the moon has set up shop and is now gobbling down spacecraft as quickly as we can send them. Only, as you said, Blue Ghost has successfully stuck the landing in, in a while. So yeah, it's been, uh, well, there was the second, the Chandrayaan three, the other Indians.

Dr. Pamela Gay: 

So yeah, India, India eventually succeeded.

Fraser Cain: 

Yeah.

Dr. Pamela Gay: 

Um, but.

Fraser Cain: 

And Israeli, two Israeli. Yeah. Yeah.

Just gobble, gobble, gobble, yum, yum, yum.

Dr. Pamela Gay: 

Bear Sheath had a bad day.

Fraser Cain: 

Yeah. Bear Sheath had a bad day. Yeah.

Dr. Pamela Gay: 

Poor tardigrades. Um, anyways, anyways, so they landed in the bottom of a crater on the far side in the Southern hemisphere, basically going, we're here. We did it.

They extended their arm. They scooped up a sample. They extended their drill.

They drilled up a sample. They were able to get two different kinds of basalts, uh, which is basically solidified lunar lava. Um, and, and they've discovered in looking at this, that there is the potassium.

There's the rare earth elements. There's the phosphorus, all of the creep stuff. And they were able to use a variety of radioactive elements to also measure the age.

And some of the basalt was as expected about 4.2 billion years old. But the other sample was less than 3 billion years old, which tells us that there was active volcanism for significantly longer than expected. Um, now with, with the Chang'e 5, we, Che'an 5?

I'm going to mispronounce. How do you say it again? I'm asking.

Fraser Cain: 

Chang'e, Chang'e.

Dr. Pamela Gay: 

Chang'e 5.

Fraser Cain: 

Chang'e 5 and Chang'e 6.

Dr. Pamela Gay: 

So with the Chang'e 5, uh, they, after three years released, uh, some grains of the sample to be, uh, researched by non-Chinese researchers. We have not gotten past that three-year date. Uh, so we're, we're still waiting for release of these particles for more experiments to be done.

Um, but from the, the research that they've had, and there was a very impressive paper in nature that came out, um, they found that volcanism persisted for over 1.4 billion years. Um, and, and that is, is new. So they, they were using the uranium to, uh, lead, um, ratio.

Um, and this is also the, the 4. billion year sample is the oldest sample so far returned. So they have this great dynamic of really old chunk, younger chunk, allowing us to span all the eons of volcanism that occurred.

Now, things that, that we're hoping for with this is one of the things that makes the South Aitken Basin, uh, region so exciting is when that was excavated, bedrock should have gotten flung up to the surface. So the, the two bits that have been discussed so far are both basalts. So the question starts to become, are they also going to find any bedrocks in the sample?

What else is going to be in there? So we have one paper so far, um, here is hoping for more papers that bring us more information on was there bedrock, uh, what all is, can we learn about the difference between the near side and the far side? We would love to be able to figure out, is this actually two different moonlets that combine to form one great big moon billions of years ago?

Fraser Cain: 

Yeah, that's one of the, one of the sort of theories, right? Is that, you know, why is the far side of the moon so heavily cratered while the near side of the moon is, is more volcanic.

Dr. Pamela Gay: 

And the gravitational center of the moon is closer to the near side than the far side. They have very different densities.

Fraser Cain: 

Yeah. Yeah. And one of these ideas, as you said, is that there was actually a second moon and it crashed into the far side of the moon.

And then that sort of added more depth to the, to that and push the center, as you said, more to the, the, the near side until the volcanism erupted from the near side of the, of the moon. But it is still definitely an ongoing mystery. You know, that was one of the big surprises when we got the first spacecraft had ever gone around the far side of the moon.

It was like a Soviet with a Luna 2. Anyway, one of the, the Soviet missions had, had taken pictures of the far side of the moon. And suddenly you saw this world look totally different than the, than the near side.

Um, and you know, one of the things that was interesting with, with Chang'e 6 was that they, there was an international collaboration. So there was, uh, instruments on board from other countries, Italy, uh, and with Chang'e 5 and with Chang'e 6, there's this sort of sharing of the, of the information with other nations. Uh, they have like a three-year headstart, I think.

And then they give the samples out to, to other nations as sort of part of their agreement as well. So, you know, people always ask, you know, what are the Chinese sharing this information out to, to other countries? And they, they definitely are, you know.

Dr. Pamela Gay: 

There's a French instrument called Dorne, which I don't know why that like, why the name amuses me, but it was looking for outgassing from radon or outgassing of radon. Um, there's an Italian instrument, uh, that's doing laser retro reflector investigations.

Fraser Cain: 

So you can like measure the distance to the, to the moon, although it's tough on the, on the far side, but yeah.

Dr. Pamela Gay: 

Well, and, and then there's a Swedish negative ions on lunar surface, which is literally detecting negative ions reflected by the lunar surface.

Fraser Cain: 

Yep. And then of course you mentioned it had the, the Jin Chan, uh, mini rover, which crawled away and then, and took some pictures and did some other, uh, work as well. So there are some more Chang'e missions in the works before we see humans.

So let's talk about seven and eight. Chang'e seven is going to go this, this year. Um, and it is going to be a lunar scout, uh, and they're going to try and land in Shackleton crater near the lunar South pole.

And they're going to have a, uh, a, like a hopping probe. That's really cool. That's going to sort of hop around on the surface of the, of the moon.

Uh, and then, uh, like bring a, bring a ton of, uh, of size to the surface of the moon. And then, uh, Chang'e eight is going to be one where they're going to be doing, um, and that's going to be in 2028 and that one they're going to be doing, uh, going to be testing out, well, they're looking at potential landing sites for, uh, upcoming human mission from the Chinese astronauts. And they're going to be doing a bunch of testing of some of their institute resource utilization technologies, you know, the ISRU.

So they've got a 3d printer on board this, this, uh, lander that's going to be shoveling in lunar regolith and then spitting out, uh, precision 3d elements from it that then you could build bricks. You could build, uh, you could build stuff that, um, you know, could be used in the construction of a, of a future habitat. And, and then, you know, that sets the stage for 2030, which is, which is when the, um, in theory, the, the human mission is going to be going to the moon and, you know, have you been following sort of their plans for the, for the human mission?

Dr. Pamela Gay: 

I know it's two astronauts. I know they're using their Long March 10.

Fraser Cain: 

Yeah. They've got a new version of the Long March, a heavy lift version of the Long March that they're working on. Uh, and it's going to be two separate rockets.

Dr. Pamela Gay: 

Yes.

Fraser Cain: 

One, which carries the crew and the service module, uh, and then one in the, in the command module, and then one that carries the lander and the rockets are going to meet up in lunar orbit. Yeah. And then the crew is going to transfer from their, from their capsule to the lander, go down to the surface of the moon, frolic about on the surface of the moon, fly back up to orbit with their ascent module, return to the capsule and then return to earth.

And, and this is very different from the, the Saturn five mission where they, you know, we think about it, they had the whole stack on the one rocket. And this is also extremely different from the plans from NASA, which is where you've got the crew on the space launch system. And then you're going to have the starship or blue origins.

Dr. Pamela Gay: 

Or mark two. I think it's very similar to blue origin, actually.

Fraser Cain: 

Yeah. In either case, there's going to be a lander that is going to have to be refueled in, in earth orbit and then flown out to lunar orbit that then the astronauts will arrive at dock with, get in, go down to the surface of the moon, come back up and then return. So it's, you know, you won't have all of the refueling that you will with the, with the American version, but it's also a much lighter weight process.

Dr. Pamela Gay: 

So it's, it's similar to what we were thinking could happen with a blue origin modified for use in 2028. So there's currently two different blue origin landers under development. One is let's just get her done.

And the other is the reusable future one. So I think the US get her done and the Chinese are fairly similar in, in concept.

Fraser Cain: 

But I would not be surprised if the US in the end follows the same plan that the Chinese are going with, where you have a, you have the space launch system, carry the astronauts in the Orion capsule, and then you have a second rocket, probably a blue origin, maybe a Falcon heavy carrying a lander out to lunar orbit. And then they make the transition over and get into it and go down to the surface of the moon. Like that just seems much closer to what the, except no lander exists yet, but it's, it's in the works by both SpaceX and blue origin.

Dr. Pamela Gay: 

And they're looking to go to the South pole. And what's cool is with the, the lunar samples that they were able to get with mission six, they, they showed that the crater age dating scenario that we have on the near side appears to play out on the far side, where when you count the number of, of craters, you get an age and the ages match on both the near side and far side, which means we have the same cratering rate on both sides. But one sample from one place is not enough to verify that, but they are sticking to the South pole region, which is also where we're looking to find water in these ancient craters.

There was a paper that came out either last week or the week before showing that the longer crater has been around, the more water will have had time to accumulate inside of it. So these ancient craters really are where you want to go and they just found the oldest sample so far found. So go team, go Apollo crater.

Fraser Cain: 

Yeah, yeah, yeah, absolutely. So, uh, so keep your eyes peeled. So we're going to have that the, the Chang'e 7 is going to launch later this year.

Chang'e 8 is going to launch in 2028 and then by 2030, and then the other big launch that's going to happen. And I know you don't think about the future. So allow me to give me a second here, which is that in 2028, they're going to launch their Mars sample return mission.

And so by probably 2031, we will have samples of Mars in the hands of scientists here on earth. Not the full, you know, not the nice samples taken by Perseverance, but still, and it's the same technology, right? You can see this same technology stack is being tested out on Mars.

And then what comes after a Mars sample return is probably a Mars human mission. So, uh, you're sort of watching the technology be tested stage after stage, step after step.

Dr. Pamela Gay: 

And one of the, it's, I mean, they're slow in study. They're massive financial investment. They're doing it right.

There, there was a NASA office of the inspector general report that came out today that expressed concern that just the EVA suits for the Artemis mission are in extreme jeopardy right now. Um, because NASA moved to using fixed cost contracts, which means they're saying, hey, company X, go innovate this thing that no one has ever done before.

Fraser Cain: 

And eat the cost if you fail.

Dr. Pamela Gay: 

And eat the cost if you fail. And, and OIG is like, yeah, they're behind this problem, problem, red alert, danger, Will Robinson. And, and so we're in a position where we're asking commercial companies to innovate where NASA assists with the costs, but there's no profit scenario.

There's no lunar economy right now. And so until there can be a lunar economy that drives innovation in the name of future profits, why are companies going to worry about being on time, um, in their development? There's no motivation.

Fraser Cain: 

So, yeah. And this has nothing to do with the Chinese Air Force missions.

Dr. Pamela Gay: 

No, it's just sort of like, it just sets the playing field. Yeah.

Dr. Pamela Gay: 

Yeah. It's the false economy of the space race.

Fraser Cain: 

All right. Thanks Pamela.

Dr. Pamela Gay: 

Thank you Fraser. And thank you everyone out there in our Patreon, who is so tolerant of my failure to know phonics or pronounce anything correctly as this episode has shown. And we would now like to thank all of you at the $5 a month level and higher.

Our show wouldn't be here without the amazing support of so many of you over on Patreon. I'm now going to try and thank you by name and I am really bad at phonics. So thank you.

And I'm sorry for what I'm about to do to your name. This week we would like to thank a pronounceable name, Abido Bear, Alex Rain, Andrew Allen, Andrew Stevenson, Arno DeGroot, Bebop Apocalypse, Benjamin Carrier, Buzzy Gowen, Buzz Parsec, Cammy Rassian, Christian Bearcolt, David Bogarty, Dr. Wo, Frederick Salvo, Frank Stewart, Frodo Tanenbach, Gerhard Schweitzer, Greg Davis, Greg Vild, Hannah Tackery, J. Alex Anderson, Jeff Wilson, Joe McTee, John Drake, John Herman, John Vays, J.P. Sullivan, Kim Barrow, Christian Golding, Labrat Matt, Les Howard, Lou Zeeland, Mark Schneider, Mike Haizu, Rhythm Chameleon, Robbie the Dog with the Dot, Robert Cordova, Robert Hundle, Ron Thorson, Rizzard with a Z, Sergio Sansevero, Sam Brooks and his mom, Shersom, Scott Briggs, Semyon Torfason, Sergei Monolov, The Big Squish Squash, The Brain, The Lonely Sandperson, Wanderer M101, Will Hamilton. Thank you all so very much.

Fraser Cain: 

All right. Thanks, everyone. And we will see you next week.

Dr. Pamela Gay: 

Bye-bye, everyone.

Live Show

Even though humanity has returned samples from a fraction of the worlds in the solar system, the cosmos has delivered many more without us having to lift a finger. Meteorites. We have meteorites from the Moon, Vesta and even Mars! What have we learned about these rocks from other worlds? Space missions to other worlds cost millions to billions of dollars, and if we want to know exactly where space rock samples come from, we need to spend the big bucks for sample return. But, if it's good enough to know "this rock came from somewhere on that world," space offers an amazing delivery system in the form of meteorites. Come learn about the search for, identification, and science of meteorites from other worlds.  

Show Notes

• Meteorites as samples: Natural delivery from Moon, Mars, Vesta, asteroids
• Impact ejection: Collisions launch rocks into space at escape velocity
• Scientific value: Reveal early Solar System chemistry & planetary history
• Limitations: Unknown exact origin, shock damage, Earth contamination
• Identification methods: Spectroscopy, composition matching, trapped gases
• Crater studies: Tektites, shock features, and local knowledge
• Life debate: Controversy over possible biosignatures (ALH meteorite)
• Sample return vs meteorites: Precision vs accessibility
• Possible sources: Mars, Moon, Vesta, Phobos, maybe beyond
• Interstellar material: Difficult to identify but potentially present
• Key takeaway: Meteorites = accessible clues to planetary and cosmic history

Transcript

Fraser Cain: 

Astronomy Cast, Episode 790 Meteorites from Other Worlds. Welcome to Astronomy Cast, your weekly facts-based journey through the Cosmos, where we help you understand not only what we know, but how we know what we know. I'm Fraser Keane, I'm the publisher of Universe Today.

With me as always is Dr. Pamela Gay, a senior scientist for the Planetary Science Institute and the director of CosmoQuest. Hello, Pamela.

Dr. Pamela Gay: 

Hello, Fraser. I have a new favourite moment in Rule Breaking. Can I share it?

Yes. So, Astronaut Commander Reed from the Artemis II Integrity Capsule was supposed to leave RISE, the little round plushie that they had as a zero-g indicator. He was supposed to leave it on board Integrity as it floated in the ocean, hopefully to be rescued, and he couldn't do it.

He couldn't leave behind RISE. So he stole it.

Fraser Cain: 

You don't leave a crew member behind. Right.

Dr. Pamela Gay: 

Snuck it out. So RISE now is Commander Reed's, and he's been just like kind of carrying it around in lots of different... It is my favourite moment.

Fraser Cain: 

Isn't it supposed to end up at a school, though, at some point? Like it's going to end up with some... I forget how...

Dr. Pamela Gay: 

I don't know. I just know it wasn't left behind on the capsule, and there are so many adorable photos. And yeah.

Fraser Cain: 

Man, that mission was so great. I was just transported to a younger version of me watching sort of the one that actually felt most significant to me was the Mars Pathfinder Sojourner mission. That was the one that I was really just glued to the live streams, watching every moment.

And this brought me back to that world, watching all of these key moments, even just sort of switching back to see the live stream, the quiet view of the porthole of the Orion capsule to see either the Moon or the Earth. It was absolutely incredible. And it just shows us the best of what humanity can do.

And obviously, there are details about the $4 billion that it cost to launch these things, the delays in the launch, the potential competition from reasonable rocket companies and so on and so forth. But still, this was just... Humanity went farther than humanity has ever gone, and I was there for it, and it was incredible.

I think we should do an episode about Artemis 2 when we have a little bandwidth. Even though humanity has returned samples from a fraction of the worlds in the solar system, the cosmos has delivered many more without us having to lift a finger. Meteorites.

We have meteorites from the Moon, Vesta, and even Mars. What have we learned about these rocks from other worlds? Meteorites.

Meteorites. Which worlds do we have meteorites from that have fallen down here on Earth?

Dr. Pamela Gay: 

Mars, the Moon, Vesta series, a whole bunch of the other asteroids, but they come in families, which makes it a whole lot harder to say exactly which one they came from.

Fraser Cain: 

Right. They came from this family. Who knows if it was...

Which of the specific rocks?

Dr. Pamela Gay: 

I'm pretty sure we don't have any from Venus, but...

Fraser Cain: 

No, we don't.

Dr. Pamela Gay: 

Okay. You often prove me wrong, so I have learned to add caveats.

Fraser Cain: 

That would be wise, yeah. No. From what I understand, there are none from Mercury, none from Venus.

Dr. Pamela Gay: 

The energy from Mercury is not realistic, and Venus's atmosphere is just super thick.

Fraser Cain: 

Yeah. Nothing's getting out of either of those. Yeah.

Yeah. Okay. And that is incredible.

So how do they get here?

Dr. Pamela Gay: 

Well, when a rock hits a rock, transfer of momentum is expletive. So what ends up happening, and this is part of my favorite caption that has ever existed in a print magazine. There is this amazing caption that I believe based on the formatting of the page that I found on Reddit, came from Scientific American.

I've not been able to find the actual article. The caption basically reads that when the asteroid that killed the dinosaurs struck Earth, the shock wave flung at escape velocities, dirt, trees, and dinosaurs. And...

Fraser Cain: 

What a way to go.

Dr. Pamela Gay: 

Yeah. Yeah. So the first life forms to leave the planet Earth were very dead dinosaurs.

Fraser Cain: 

Right.

Dr. Pamela Gay: 

But...

Fraser Cain: 

I mean, probably very dead.

Dr. Pamela Gay: 

Many other things.

Fraser Cain: 

Many other things. Yeah. When you think about the giant impacts that have happened in the history of planet Earth, there was some early first astronaut.

Dr. Pamela Gay: 

So when space rock comes down, whether it be something tiny that just becomes a meteorite or something bigger where you just keep calling it an asteroid, when it collides, that kinetic energy from its motion ends up getting translated into heat, into noise, into compression waves moving through the ground. And that energy excavates the crater, melts a lot of stuff, flings boulders in all directions as it does its excavating. And some of those things that it flings are going to be going at escape velocities from whatever world is getting hit.

And those excavated chunks of world are then on their own orbits that could include a trajectory that heads them straight towards us. And this leads to all sorts of mixing of early solar system substances back when collisions were much more common between the early forming worlds that, well, Venus, Earth, and Mars were all settling into habitability at about the same point before Mars decided to become too cold and Venus decided to become way too hot.

Fraser Cain: 

So let's talk about some of the samples that have been found and some of the most interesting ones. And I mean, I think, I mean, this is not the same as a meteorite that is out in space. This is not the same as us retrieving a sample from an asteroid or from a comet.

When you think about, say, Hayabusa, Hayabusa 2, Cyrus Rex, they pulled a chunk, they pulled material off of these objects. And these were in a pristine state. I mean, obviously they're rubble pile asteroids, they've gone through, they've seen some things, but they haven't sort of experienced the same kind of shock and damage that has happened from something that was actually scoured out of another planet.

Dr. Pamela Gay: 

Yeah. We have three scientific problems with donated samples from other worlds. One is we don't know exactly where on that other world it came from.

Fraser Cain: 

But even, well, so hold on, I was going to bring that up, but actually they're starting to get a sense of where some of those samples came from.

Dr. Pamela Gay: 

For some worlds, but we can't consistently do it.

Fraser Cain: 

The Mars ones, they're getting a sense based on the kind of, I mean, we know so much about the rock on Mars that we can guess where those samples might've come from roughly.

Dr. Pamela Gay: 

But we can't do the kinds of things that we do with like collected lunar rocks where we take them into a lab, we measure exactly how old they are, and then we can use them to calibrate our understanding of how old different surfaces on the moon are. We can't do that.

Fraser Cain: 

No. And then like think about what's happening with Perseverance as it is going across the landscape of Mars, looking for the perfect rock and then drilling a sample, holding it closely inside its sample container, moving on. Like that is precision in what you get as opposed to what you get with just random rocks being hurled at the planet.

Dr. Pamela Gay: 

Right, right.

Fraser Cain: 

So that's the first challenge. You don't know where they came from.

Dr. Pamela Gay: 

Right. So first challenge is you don't know where they came from. Second challenge is they're getting altered by the space environment a whole lot.

So there was whatever excavated them was a high energy event. They traveled through space, which causes surface weathering. And then they went through our atmosphere, which causes its own form of challenge as it gets heated up and then smashes into whatever it smashes into.

Fraser Cain: 

Yeah. And that's probably not the worst part of the contamination. The worst part is that they then sit on the surface of the earth for an unknown amount of time being infested by our local life forms.

And that one of these meteorites can be hidden for hundreds, thousands, tens of thousands, hundreds of thousands of years.

Dr. Pamela Gay: 

Hundreds of thousands is pushing it because we do get them from places like deserts and ice flows and our planet has had weather cycles.

Fraser Cain: 

Right. But the point being that that's plenty of time for occupation to occur. Yeah.

I mean, what probably happens is that the various weathering process that we have on the earth dismantle the meteorites within that timeframe. So it's the ones that we get to them before they're completely faded away. But still we can do science.

What kind of science can we do with these samples?

Dr. Pamela Gay: 

So there's the straightforward, which is you take them into a lab, you cut them into very thin slices and you study what is the stuff inside them. What is the components? And this is useful for two different reasons.

One is we can also shine light at them and reflect the light off and match them to other worlds. This is actually how we figure out what meteorite came from, where, when it comes to the asteroids is we know the asteroids really well in reflected sunlight. You take a space rock, take it into your lab, reflect sunlight, sun, light off of it and see what it matches.

And that's its parent body. And then, because we don't have samples of Vesta, we don't have samples of Ceres, we don't have samples of like all but just the tiniest handful of asteroids. So then we take them apart and look at them to measure the various mineral structures, to measure the various, how does all of this stuff come together and then shred them completely in a mass spectrometer to get at the atom by atom understanding.

And some of the thin cuts that they do through these and then shine light through look like the most amazingly chaotic stained glass. So our solar system is out there creating chaotic stained glass and sending it our way.

Fraser Cain: 

But I think one of the most exciting things is that there is gas trapped within these rocks.

Dr. Pamela Gay: 

Yes, I have to admit that is one of the things I am, I am weirdly just less interested in. But we have found both liquid and gas trapped inside the crystalline structure of various minerals. It turns out things like diamonds in particular are very good at holding stuff in their inclusions.

So when we get particularly lucky, we're not looking for amber containing animals, we're looking for minerals containing gas, containing liquid, containing a moment in the history of another world.

Fraser Cain: 

Yeah, yeah. I mean, again, this is just incredible when you think about this, that a giant asteroid smashed into Mars, scoured out material, sent it into orbit. These rocks have been floating around in the solar system.

And then some part portion of them found their way to the Earth's atmosphere, enter the atmosphere, reached the ground, a scientist found it, and then sliced it open. And there were bits, there were tiny bits of trapped Mars atmosphere in that meteorite that you can then use to study the atmosphere of Mars at the time that the space rock was hurled into space. What have we learned, do you think, about being able to study these samples from other worlds?

Dr. Pamela Gay: 

One of the first things we've learned is what makes someone a scientist is when they find something cool, they report it. Because so many of the meteorites that have been found that weren't in Antarctica where we send groups of humans who have been trained to find meteorites to go find meteorites. A lot of the other ones that have been found are like someone's back pasture, someone's back 40.

So farmers are one of the great sources of meteorites. Yeah, all over the world, people find meteorites and when we're lucky, they report what they found and they share and we get to go get samples. We have learned that there are a whole lot of unique rocks that allow us to look at things and go, this is actually a crater right here.

Because when the impactor is big enough, it creates tektites, which are melty bits of the rock that was already there that now become new rocks. And it creates these shocked rocks where you can actually look at them and see through, they're called shock cones, go figure, we're not exciting in how we name things. So there's all these local ways geology gets wrecked when big things hit and it changes the landscape.

And there's this one really funny case of a winery in France that was creating meteorite wine. And they were claiming that their vineyard, which is in this cool circular indentation, was a meteorite crater and everyone was like, ha, ha, ha. And it turned out that some geologists who were traveling, who of course went because it was funny, were like, oh, oh, wait, this might be a crater.

And so they went back and it was actually a crater. And I'm super sad because you can't get this wine in the United States and I really want a bottle. So folks in France, I really want a bottle of this wine.

And so we have learned that we need to listen to the locals. We need to listen to their stories. We need to listen to like oral traditions are a great way to figure out where craters formed in the past at various points in history.

And then when we pick up these rocks, we also learn to be slightly afraid because they could be carrying stuff from a point in time where life existed on other worlds than this.

Fraser Cain: 

Right. And I think we need to talk about one of the most controversial rocks found from another planet, Allen Hills. So this is going to be a moment that is kind of seared into everybody's memory.

And this happened at roughly the same time that I was enthusiastic about watching the Mars Pathfinder mission complete its various operations. Shortly after that, we saw the announcement of life on Mars. Thanks to the Allen Hills meteorite.

Dr. Pamela Gay: 

Yeah. And back in 1984, this meteorite was found on Allen Hill in Antarctica. And it takes a while for them to get through all the different meteorites they find and do research on them.

And this particular one, they found it, they sorted it. And then Roberta Skor, who's the lab manager at Johnson Space Center, she was the one who found it. And it was claimed to be the oldest Martian meteorite that had been found to be 4 billion years old.

And when folks started studying it, one of the things that the research team did was they cut it, they gold plated it, they put it through an electron scanning microscope. So the gold plating was to make the electron scanning microscope work better. And when they looked at the images that came out of the electron scanning microscope, they saw what looked like little tiny nanobacteria nodules that were similar to what had been studied at places like Yellowstone.

And the claim was made that life had been found in the Allen Hills meteorite. Now this was super controversial for a number of different reasons. One was it turns out if you're not like the absolute nicest person on the entire planet, people are going to show more skepticism to your research.

And when we were all going to see the talks on this, the person presenting, whose name I'm not going to name, would show the meteorite, would then show pictures of his grad students in skimpy clothes next to where they collected the nanobacteria from field sites. And that didn't sit well with many of us. And so there's that underlying, blech, that just like kind of went into how you looked at the research.

And then there was like the knowledge that if you screw up your gold plating, you get artifacts that look exactly like what they were saying was nanobacteria. And then there's like the fact that just sometimes minerals do stuff. And they haven't really allowed the experiment to be replicated.

So you have this situation where no other means of exploration have been able to replicate what they found. Other work done on the same meteor didn't find indications of life. And there was just kind of this overall, blech, involved in the research.

So, yeah, they might have found something. But until it gets found in a more credible way, and likely until it's presented by someone that doesn't leave all of us feeling slightly creepy, it's life hasn't been discovered.

Fraser Cain: 

Yeah. And I mean, I think you've got to sort of compare this to what happened with, say, the Hayabusa and the OSIRIS-REx mission. You had these samples returned.

They were sent out around the world to dozens of teams with some of the world's best labs. And they've been trickling back their information, confirming each other's discoveries, finding all these amino acids and all of this sort of measuring the amount of water in these samples, and determining a lot of really interesting things about the early history of the solar system. And that this is, you know, partly that when a rock from space lands on Earth, it is just one rock.

And then it's up to the team who claims it to work on it to sort of decide how the information is sort of parceled out. And that if you have a really bombastic discovery, it is tricky to then put yourself to that level of scrutiny. And yet that's what science demands.

That's how science works. As opposed to this sort of top-down, hey, we've got all these samples, here you go everybody, get back to some of what you found. And then they're kind of double-checking each other.

So it's, yeah, it's, unfortunately, I mean, we have a lot of examples of this. We have the Viking, we have the Allen Hills meteorite, we have the discovery of phosphine in Venus, we have the detection of methane on Mars, we have Mono Lake, yeah, we have all these times where life was found, and yet it just didn't hold up to scrutiny. The wow signal, like it just, it goes on and on and on.

The discovery of satellites in orbit around the Earth before the first artificial satellites were launched.

Dr. Pamela Gay: 

The Japanese UFO on an archaeological thing, yeah.

Fraser Cain: 

Boyajian's sort of dust ring, like it goes on and on and on. And it just shows that when the potential consequences of the discovery are big, then the level of rigor and the amount of sort of ego setting aside needs to be done is astronomical. And few are up to that task.

Dr. Pamela Gay: 

And you really need to have no clear alternative answers because Occam's Razor is a thing. And when you can say, yeah, but if you gold-plated it not perfectly, that's exactly what it looks like. That is such an easy explanation for what they saw, and it's not like you can un-gold-plate the meteorite.

Fraser Cain: 

Right. Yeah. So let's talk about kind of hypothetical meteorites.

Yes. Could there be meteorites from Mercury, Venus, Phobos, Io here on Earth somewhere?

Dr. Pamela Gay: 

Phobos, yes, that's easy. Io, I mean, it could happen, but it's going to take a whole lot. And the idea of something being big enough, having come off of Io, traveled this way and made it through our atmosphere, my brain is going, but it's a gooey world.

I mean, it's not all gooey, but that's where my brain went is it's gooey. Yeah.

Fraser Cain: 

I mean, it's covered in rock.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

You hit it with an asteroid, it's going to blow up rocky chunks into space. They're not going to remain lava.

Dr. Pamela Gay: 

Yeah. You just have to hit it really, really hard because of Jupiter's gravity.

Fraser Cain: 

Yeah. Yeah. You have to escape Jupiter.

Dr. Pamela Gay: 

Yeah. You have to escape Jupiter's gravity, which means that you have to somehow dig deep enough to get a whole lot of boulders sent out at a whole lot of velocity. So, Io is giant question mark of could it happen?

Well, a lot of things can happen, but I put the probability on that one super low. Venus.

Fraser Cain: 

What about? Oh, Venus.

Dr. Pamela Gay: 

Okay. Yeah. Venus depends on when.

So, Venus hasn't always had the atmosphere it currently has. And so, if you hit it really, really hard when it didn't have that super thick atmosphere, but had already solidified and before it got its prior atmosphere flung off, yes. So, I mean, it's always had an atmosphere.

It just hasn't always had its current atmosphere.

Fraser Cain: 

But it is tricky to climb up that gravitational well.

Dr. Pamela Gay: 

But if you can fling dinosaurs that escape velocity off of the planet Earth.

Fraser Cain: 

Yeah. But you not only have to fling them off of a world that is as much as.

Dr. Pamela Gay: 

You have to escape the sun.

Fraser Cain: 

Yeah. You have to escape the sun.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

That is the challenge. You have to get, you have to climb, like people always sort of imagine Venus in this sort of, or these worlds in this sort of perfect balance and you just drift away from one to the other. But no, the sun is this giant gravitational well.

It is at the bottom of this gravitational well. Mercury has partially climbed out of this gravitational well. Venus is a little better and Earth is a little higher.

Dr. Pamela Gay: 

Yeah.

Fraser Cain: 

But to go from Venus up to Earth, it literally is up to you. You've got to climb a mountain and that is a challenge. Of course, it's also difficult to climb down the mountain.

Dr. Pamela Gay: 

Right.

Fraser Cain: 

Both are challenges.

Dr. Pamela Gay: 

And this is where you have to be looking for things that are on elliptical orbits that intersect both Venus's orbit and Earth's orbit because that is easier to accomplish. And as always, your friendly reminder that it is far easier to yeet things out of the solar system than to yeet them into the sun.

Fraser Cain: 

Right. What about an interstellar object?

Dr. Pamela Gay: 

Oh, yeah. I'm sure we have interstellar objects on our world. Yeah.

We just don't have a reflection spectrum to match them to. So it's probably like unlabeled mystery rock.

Fraser Cain: 

Right. But you can imagine someone doing, say, a sample of it, looking for the radioactive decay and then going, wait a minute, this sample is 8 billion years old. Right.

This rock is 8 billion years old. Like in theory that it's never been found. Right.

All of the meteorites ever been tested have always been exactly the same age, the age of the solar system. But out there somewhere, there is a meteorite that will, when you test it. Now, they've found pre-solar grains in meteorites that are older than the solar system.

Dr. Pamela Gay: 

But those are grains.

Fraser Cain: 

Grains. Not full meteorites. And yet you think, you know, we have, we've seen three interstellar objects passing through the solar system.

Dr. Pamela Gay: 

Models show there should be like 6 to 12 a year.

Fraser Cain: 

Yeah. And there should be probably 10,000 plus just going through the solar system at any one time. And so at some point in the past, an interstellar object has struck the earth and it's there somewhere on the planet for the finding.

Yeah. And then can you imagine what we could learn studying a rock that came from another planet in the galaxy?

Dr. Pamela Gay: 

The frustration of not knowing its provenance is the great frustration.

Fraser Cain: 

Yeah. Yeah.Yeah.

Yeah. Yeah. It's just like, you know, it's made of different stuff.

I mean, it would still be made of the same kinds of material. But the ratios will be different. Slightly different ratios.

Yeah. Yeah. And it's older.

Dr. Pamela Gay: 

Right.

Fraser Cain: 

Be like, oh, it formed a billion years ago. But we don't know where. Like maybe you could look at the chemistry of stars out there and find one that it's We can't even find our own siblings.

Dr. Pamela Gay: 

Yeah. We orbit the center of the galaxy, I think every 250 million years.

Fraser Cain: 

Yeah. Yeah. And so a lot of potential siblings of the sun have been found.

Dr. Pamela Gay: 

Right. But we can'tprove it because we've scattered to the four directions, inward, outward, forward and back. Yeah.

Fraser Cain: 

Yeah. Yeah. But that'll be that'll be incredible if there's some time like people have proposed that the trajectories of certain meteorites coming in, hit the atmosphere, that they were on an interstellar trajectory.

There was a search by Avi Loeb and others to try and find a meteorite, but the results were inconclusive. So we are still waiting for that. And then probably the best thing is to just chase down an interstellar object and sample it directly and bring a piece home.

That will be the greatest accomplishment of humanity, I think, is to be able to chase down.

Dr. Pamela Gay: 

And you just did a video on that. Have I? You just did a video on chasing down meteorites.

Fraser Cain: 

Yes. Yeah. Yeah.

Well, those are ones in the Earth's atmosphere.

Dr. Pamela Gay: 

Okay. That's true.

Fraser Cain: 

That's true.

Dr. Pamela Gay: 

So the meteor, meteorite, meteoroid set of words.

Fraser Cain: 

Yeah.

Dr. Pamela Gay: 

Just put all of this into your heads. Meteoroids, asteroids are space rocks still in space. Meteor is while they're going through the atmosphere.

Meteorite is once you've picked them up because minerals and an ite. Yeah. So these words are evil.

I just call them space rocks.

Fraser Cain: 

Yes. And people love to give you a hard time if you... Confuse them.

...don't get it perfectly right. But I think there's a lot of edge cases where you kind of wonder, you know, does a meteor hit the moon?

Dr. Pamela Gay: 

A meteoroid hits the moon.

Fraser Cain: 

Yes. But what if it's a kilometer across?

Dr. Pamela Gay: 

Then it's an asteroid.

Fraser Cain: 

It's not a meteoroid. I think, you know, I think meteors can hit the moon.

I think, you know, I think meteors can hit the moon. I think if they're on a collision course with the world, that that's when they become a meteor, in my opinion. But anyway, I think we've wrapped up this topic.

We're now starting to rabbit hole. So thanks, Pamela.

Dr. Pamela Gay: 

Thank you, Fraser. And thank you so much to all of you out there. Being able to continue doing science communications in this day and age where we're seeing NASA literally cancel the entire office of science communications.

It is an honor and a pleasure. This week, I would like to thank our patrons over on patreon.com slash astronomycast, who allow us to have Rich, Ali and others, Aviva, making sure we don't sound terrible. This week, we are pleased to thank the following people whose names I shall now mangle.

Our show wouldn't be here without the wonderful support of so many of you over on patreon.com slash astronomycast. This week, I'm going to thank you the best way I have, which is by probably mispronouncing your name. Thank you so much to Antisor, ArcticFox, AstroSets, Benjamin Mueller, Bob Zatzke, BoogieNut, Breznik, Brian Kilby, Cody Rose, Conrad Holling, Daniel Schechter, David, David Gates, David Green, Diane Philippon, G.

Caleb Sexton, Galactic President Scooper McScoopsalot, Glenn Phelps, Gold, Jared Heal, Janelle, Jason Kwong, Jeremy Kerwin, Jim Schooler, John M, Jordan Turner, Laura Kettleson, Lee Harbourn, Lana Spencer, Marco Irrasi, Matt Rucker, Michelle Purcell, Michelle Wichman, Nala, Nate Detweiler, Older, Patricia Hope, Paul D. Disney, Randall, Richard Drumm, Robert Palasma, Sachi Takaba, Sandra Stantz, Sean Matz, Siggy Kemmler, Slug, TC Starboy, Thomas Gutzeta, Tiffany Rogers, Timeroid Iroh, Tricor, Tricia McKinney, and Vettely. Thank you all so very much.

And I'm so sorry for my failure to pronounce things.

Fraser Cain: 

All right. Thanks, everyone. We'll see you next week.

Dr. Pamela Gay: 

Bye-bye, everyone.

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