Ep. 656: Smashing Asteroids for Science! (1)
Fraser: Astronomy Cast Episode 656: Smashing Asteroids for Science. 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 Cain, the publisher of Universe Today.
I've been a space and astronomy journalist for over 20 years. With me is Dr. Pamela Gay, a senior scientist for the planetary science institute and the director of CosmoQuest. Hey, Pamela. How you doing?
Dr. Gay: I am doing well. We have hit the month of October, and all my Halloween decorations are going out. And Jupiter is at opposition. And these things have nothing to do with each other, but both bring me joy.
Fraser: Yeah.
Dr. Gay: Have you seen Jupiter?
Fraser: Oh, of course. Yeah, hard to miss. We got out the binoculars, half the telescope – the seeing part but not the holding part – which made the whole process worthless. So, I need to go and find the tripod and get it all set up. But, yeah, it looks amazing, at least just in the binoculars. Like, there's the moons.
Dr. Gay: Yeah.
Fraser: Bands across the planet. You can see it in just my astronomical binoculars. It's such a good time. And this is the closest Jupiter has been in 60-ish years and the closest it's gonna be for decades more.
Dr. Gay: Yeah.
Fraser: If you haven't already, now is the time. And it's gonna be – this closest event has already happened. But still, it's a slow-moving, closest opposition. So, if you can, beg, borrow, steal some way to be able to see Jupiter with your own eyeballs. And while you're at it, Saturn is also up in the sky, so you can see both of them.
Dr. Gay: Yes.
Fraser: It's a good time to do some amateur astronomy.
Dr. Gay: Couldn't agree more. And a good 300-millimeter camera lens was actually my friend on this endeavor.
Fraser: Yeah.
Dr. Gay: So, yeah, I went out with one of our community members, and we got to see Galileo moons. What more could a girl ask for?
Fraser: I'm going to follow my own advice very soon and buy a 8-inch Dobsonian telescope.
Dr. Gay: Oh, yeah.
Fraser: Yeah.
Dr. Gay: Yeah.
Fraser: Our skies are so much darker here. They've been clear. But then, we've got the weirdest, clearest October I think I've ever experienced. We're breaking temperature records. And it's just been clear every day all night and perfect for astronomy. And so, I think I will bring it to a close by buying a new telescope.
All right, this week we saw the incredible image of DART smashing into asteroid Dimorphos. Now, beyond avenging the dinosaurs, what can we learn scientifically from this and other asteroid and compact, impact missions? All right. Take that asteroids! Dinosaurs, we got your back. We have avenged you.
So, did you watch the DART mission live in real-time this last week?
Dr. Gay: So, I have the greatest irony. The Planetary Science Institute where I work, we were producing a video with some of our scientists who are part of the DART mission. And instead of getting to watch the impact coverage live, I was frantically video editing the release about how we successfully smacked an asteroid.
Fraser: Right.
Dr. Gay: And there's irony in this. But I watched it after the fact, and it was absolutely amazing.
Fraser: Similar to you going and reporting on a solar eclipse and not being able to see a solar eclipse, but anyway. No, it was amazing. The footage from NASA started up about an hour before the actual impact and was just this little, gray dot in the middle of the screen.
Dr. Gay: Yeah.
Fraser: And for the first 45 minutes, it never went beyond a little, gray dot. And then suddenly it was a couple of pixels across. And then a few more pixels across. And then in the last five minutes or so, the asteroid got a lot bigger. And then in maybe like the last minute, the smaller asteroid separated from the bigger one. You realize you were going right towards the small one.
And then the big one drifted passed the field of view, and then Dimorphos just got bigger and bigger and bigger. And then it filled the screen. And then you got one last frame that was like a little ribbon of asteroid at the top and then a red stripe down below, and you knew that was [inaudible] [00:05:13]. You could see exactly where it was no longer able to transmit.
Dr. Gay: Yeah.
Fraser: And I think what made this mission different from other missions that we've seen in the past was it really felt like we were experiencing this one in real-time. I mean, it was a 45-second delay, which is not long. But you saw the images stream at what felt like video rate, which I don't think we've ever seen this before. NASA, this is all everybody has ever wanted, and you delivered it.
Dr. Gay: Yes, yes.
Fraser: So, this…but more, again. Keep doing this. And I get it; it's hard to transmit from far away. And it takes a big receiver. And there's science to be done, and so on. But still, you nailed it, literally and figuratively.
Dr. Gay: What I really enjoyed was they carried a CubeSat with them, and they like dropped the CubeSat, which popped out and unfurled. And then the CubeSat was there to photograph everything that was happening. But because the CubeSat is so tiny, it's like the worst 1980s dial-up ever experienced. And so, all those images that that wonderful little CubeSat took are going to take days, weeks, and months to get back to us.
Fraser: Yeah.
Dr. Gay: And then we have Hera getting there in 2024, which I think all of us are excited about.
Fraser: But the purpose of this episode is the value in smashing asteroids for science.
Dr. Gay: And it's not just asteroids.
Fraser: And comets, yeah.
Dr. Gay: Yes.
Fraser: And moon, and the moon, and all kinds of things. So, do you want to start most recently? Or should we start back at the beginning? When has humanity intentionally first tried to smash a solar system object for science?
Dr. Gay: The first time it was done on purpose – and the “on purpose” is very important – that was with Deep Impact. And Deep Impact had a number of different goals. It was set out to help us understand the structure of comets, the composition of comets, and to smack the bejesus out of one particular comet so that we could differentiate between what are the surface materials and what are the things that may be buried down deeper that we can only see if we dredge with our spacecraft.
Fraser: Right, yeah. And so, how did the mission work?
Dr. Gay: So, Deep Impact carried with it basically a refrigerator-sized impactor that it placed in front of the comet, and the comet smacked into it. So, NASA folks, a few of them really like to correct people and say, “We did not attack the asteroid. We simply stood in its path, and it attacked us.”
Fraser: Right.
Dr. Gay: And I love that little fact. And so, with the refrigerator-sized impact set loose, the main body of Deep Impact, which has now gone on to be called EPOXI, it collided with Comet P/Temple-1 on July 1st, 2005. Sorry, it rendezvoused on July 1st. I have to get this right because it got your Independence Day with the day that it rendezvoused, and it got my Independence Day, July 4th, with the actual impact.
Fraser: Right.
Dr. Gay: Thus, maximizing the number of holidays destroyed.
Fraser: Yeah, impacting the Astronomy Cast team. Yeah, yeah.
Dr. Gay: Yes.
Fraser: My holiday. Then you holiday. Now, what did they learn?
Dr. Gay: Well, they're primarily looking to see what is the composition of a comet nucleus. And what they found is there's clays. There are carbonates. There are silicates, the stuff of sand. But it was more the consistency of talcum powder. And there were crystalline silicates found as well.
And all of this added up to say comets carried earth, not just water. And that one gets trickstery because the kinds of water atomic ratios they found don't match our planet particularly well, but they found all these other atoms that helped enrich the environment of our world back during the age of, well, a whole lot more comet bombardments than we're experiencing today.
Fraser: So, what came after Deep Impact?
Dr. Gay: As near as I can tell, the next big thing was LCROSS in 2009. And the reason I phrase it that was is there were so many things that either didn't mean to reach out and touch an object with violence –
Fraser: Right.
Dr. Gay: – or touch something very gently. The NEAR-Shoemaker mission back in 2001 even before Deep Impact demonstrated that we have the capacity to control the spacecraft so that it will touch down lightly on an object within a 1-meter region of what it's hoping to. In this case, it's the asteroid Eros. And they just settled down and sat there for a while. They landed on February 12th, 2001. And we remained in contact with the space craft until February 28th.
Fraser: Yeah. It had no landing system. It was never intended to land.
Dr. Gay: No.
Fraser: They just were able to slowly decelerate it until it just gently sat on the surface and, I don't know, rolled over or something.
Dr. Gay: It's anticipated that it rolled over a bit.
Fraser: Yeah, they were able to communicate with it. And, of course, there were all of the spent upper-stage boosters for the Apollo mission.
Dr. Gay: Yes.
Fraser: There were al of the times that the Soviets attempted to land on Mars, other moon missions. There are craters across the Solar System that are left by unintentional spacecraft failures.
Dr. Gay: And it's not just the moon. Mars. The Beagle crash site has actually been useful in, okay, this is what a fresh crater looks like.
Fraser: Yeah, Schiaperelli as well.
Dr. Gay: Yes.
Fraser: The [inaudible] [00:11:55] mission. There's a bunch of these.
Dr. Gay: Landing on Mars is hard.
Fraser: Yeah.
Dr. Gay: It's really, really hard. But crashing fuel stages into the moon is something we have sort of, kind of continued to do on purpose. The Lunar Reconnaissance Orbiter mission did not fly alone. It was part of a two-mission launch. And on October 9th, 2009, it's companion, LCROSS, followed their second-stage empty fuel tank to the moon. Where the tank hit first, and LCROSS sent back information, sent back information, sent back, died, information. And this was when we for the first time got to see just how much water is out there underneath the surface of the moon.
The surface of the moon can only have water in the eternally shadowed regions. And places that are completely shadowed, we can't exactly see. So, with LCROSS, it hit, and it splashed out a plume of material that wasn't what we had hoped for. It turned out our models over the moon weren't quite what was – they weren't as accurate as one would hope, but there was nonetheless enough of a plume that we were able to measure water ice that was liberated from the surface of the moon during this impact event.
Fraser: That's really cool. All right, we've talked about Deep Impact. We've talked about LCROSS. Are there any others beyond DART?
Dr. Gay: So, there have been a whole series of things that were sent down onto small bodies, minor planets with the purpose of just bouncing around. Some of them bounced in ways they did intend.
