Persevering to Mars
Neil deGrasse Tyson and NASA Chief Scientist James Green discuss the recent launch of the Mars Rover Perseverance, now on its way to search for evidence of possible life on Mars. As usual, Neil is joined by his comedic co-host Chuck Nice in this explainer video from “StarTalk”.
Neil deGrasse Tyson (NDT), Chuck Nice (CN) and James Green (JG), .
NDT: Chuck, we got another explainer video ready to drop. We’ve got James Green from NASA with us to do an Explainer video on Mars, ‘cuz we are going back to Mars!
NDT: Jim, great to have you back. Remind me of your full title at NASA?
JG: I am the NASA Chief Scientist.
NDT: Excuse me!!
NDT: So Jim, you’ve got that new fancy title. Okay but also, you got into the podcast business. So what’s the name of your podcast?
JG: I did, it’s called “Gravity Assist”.
NDT: Good name!
JG: Yeah, this is actually the fourth season. Today, we’ve been taping all about the search for life beyond Earth. It’s a great season.
NDT: Excellent. Excellent. So we just launched the Mars Perseverance rover. Why didn’t we launch last year?
JG: Oh, well you know every 26 months the orbits of earth and mars line up to be on the same side of the sun, so we actually can get to mars as quickly as possible.
NDT: So it’s a window.
JG: Yeah! It’s a window. It’s much like American football, where you throw the football down the field and the receiver runs and grabs it, and that’s what we’re going to do. It’s a ballistic trajectory from Earth to Mars.
NDT: So you’re launching this to arrive where Mars will be when it gets there?
JG: On the 18th of February, mark my word. (laughs)
NDT: My boy’s got some confidence in Newtonian physics right there. (laughs)
CN: I was gonna say he better, being as I saw the budget!
NDT: So Jim, what’s different about this rover compared to the others?
JG: This one is absolutely fantastic. It’s a huge step forward because not only does it look like Curiosity, it’s got all new instruments. And one of them on the arm is a rock corer. So we are going to Mars and creating cores.
NDT: So it’s not just the surface materials? You’re going in.
JG: We’re going in and we’re gonna core rock. The rock record is so important as we know here on Earth, it’s the geology record. Same thing on Mars. So we’re going to look for aspects of climate change and whether early mars may have had life.
NDT: So where are you targeting on Mars for this?
JG: We’re going to a crater called Jesero crater. But it’s really right at the ancient shoreline of Mars. So there’s an ancient river bringing material from large regions on Mars into this crater and depositing a delta and then flowing over the crater wall into the ancient ocean.
NDT: Jim, Jim, there’s no water on Mars now. (laughs)
JG: Not at the moment! In the past! Now it turns out Mars does have an enormous amount of water; it’s just locked underneath the surface and in the northern polar cap.
NDT: But what you’re describing as this target is a place where water was formerly there.
JG: Right 4 billion years ago.
NDT: And you’re going for beach front property…
JG: You know why? We think about life coming out of our ocean, on to land, learning how to evolve and live on the land. So the ancient shoreline is where a lot of our missions go.
CN: Gotcha. So now where is the atmospheric generator buried deep inside of mars? Where would that be? (laughs)
NDT: Chuck wants to move there. Chuck wants to buy property on that beachfront. Chuck wants a condo. (laughs)
CN: You know what they say, buy on the fringe and wait! (laughs)
JG : You’d have to ask Arnold where you’d find it there…
NDT: Arnold. Send you back to Mars.
Chuck: Get your a** back to Mars! (laughs)
NDT: So, if this is styled like Curiosity was, does that mean it will arrive at Mars in the same way Curiosity did? And what was that 6 minutes of terror? Will it survive the entry? Are we going to experience that again?
JG: We are gonna use the same process. If it worked once, you know it’s not always a guarantee that it’ll work exactly the same way again. And the reason why is this rover is even more massive than Curiosity was. This rover is a little over one metric ton.
NDT: It’s the size of a car! You’re dropping a car!
CN: That’s huge.
CN: So can I ask you guys a question? When you talk about dropping this rover down into Mars okay. So when something enters Earth’s atmosphere it’s the atmosphere that’s the problem, because it’s a lot of friction – it creates all this heat. But Mars doesn’t have a lot of atmosphere, so what are the big worries and what’s the big drawback to putting something on the surface of Mars.
NDT: Wait Chuck, I have to correct you on something briefly. You’re thinking of the atmosphere as a problem.
CN: I am.
JG: It’s not.
NDT: However! The atmosphere allows you to slow down.
CN: So the atmosphere is the breaks?
JG: When we hit the top of the atmosphere, we’re going 13,000 mph. When we land 6 ½ minutes later, we’ve got to be going inches per second. And so we have a lot of momentum to take out, and it starts with the heat shield. And there’s one way to do that – Mars’ atmosphere is actually much thinner than ours and we need to travel in the atmosphere for as long as we can. So we change the center of gravity at the capsule. Instead of having it come down straight, we blow some mass, cock it this way and fly as parallel to the surface of Mars as we can.
CN: So without even having atmosphere you’re almost creating like a glider?!
JG: Well friction indeed does slow it down from that 13,000 mph to around 200 mph. Then we change the mass distribution, ride it, and pop a chute. And that chute then allows us to get it down to under 100 mph or so before we drop the rover to the surface.
CN: Okay now I’m just gonna say something. I’ve never been in a collision at 100mph before, because I probably wouldn’t be here.
CN: You say 100mph like it’s a fender bender! What happens at 100mph when you hit the ground?
JG: Well we have a platform that sits on top of the rover that has retro rockets that then take off, and slow the vehicle down.
NDT: From 100mph.
JG: Yeah, from 100 mph, slows it down and actually stops it at about 25 meters from the surface.
NDT: Which, Chuck, just to be clear, they could’ve done that upon contact with the atmosphere, but you needed fuel to slow them down from 13,000mph. So why not use the atmosphere to take most of that out, and save the little bit of fuel you’re carrying for just that last little leg. Did I get that right?
JG: Yeah! That’s right.
JG: And so what will happen then, this platform that sits on top of the rover is called the sky crane, and the reason why is we’re going to crane it down to the surface. As we start the craning, then the fact that we’ve folded up the rover and tucked it inside the capsule allows for the wheels to come out and lock, and everything gets ready for then the rover to sit down on the surface at inches per second.
NDT: So you’ve got a joist that’s unrolling for this thing to descend?
NDT: That’s crazy!
JG: No, it’s not! It makes fantastic sense when you think about it.
NDT: But there’s a lot of things – it’s like a Rube Goldberg thing. First you do the hokey pokey! You move the center of mass. You put out the drogue chute. You have the Richer Rocket. You pop the tires. And I’m thinking, aren’t those many points of failure?
CN: Lot of steps.
JG: Yeah that’s right. And we have to test each and every one of them and then try to figure out how to test them in between. But because Curiosity landed using that same approach, we have great confidence that we can repeat that, okay? So we’ll use the same procedures.
NDT: What are these features I’ve seen, it has like drone propellers or something? What is that?
JG: Ah, so in addition to the rover that looks like Curiosity, this huge rover, here’s a little model of it. Underneath the belly pad, sits what we call a technology demonstration mission, and it turns out to be the helicopter. And it’s a power rotating set of wings that then-
JG: Blades that rotate 3000 rpm and then take off. Now how we do that is we first drop it, then we get out of the way. And then we send the command, take off.
CN: That’s super cool.
NDT: And then, is it going anywhere? Does this dude go take pictures?
JG: Because it’s a test and we’ve never flown anything in an atmosphere other than Earth, this is the first flight of an object.
NDT: And you need those high rpms because of the thin atmosphere.
JG: Right, that’s right. And it’s only 4lbs. So it’s only lifting a little box that’s roughly 4 pounds. And it’s going to go through several tests. The first test is: pick up, go a couple meters up, and come down. If that’s successful, we’ll charge up the batteries and the next day we’ll do another test. Now that test will be: go up, translate, and then sit down.
NDT: Translate is code for move sideways.
JG: Yes, okay.
CN: I thought it was just going to start to learn martian. (laughs)
NDT: Translate into martian.
CN: Translate, you know “We come in peace”. (laughs)
NDT: So Jim, this mission, you speak of it as though you’re just having a conversation with the rover. But there’s the time delay of your signal. It’s like what 10 or 20 minutes?
JG: We’ll for Mars it’s orbit based on where Earth is, it can be anywhere from 4 mins to 22mins.
NDT: Okay so you can’t just say watch out for the cliff-
NDT: And it’s too late.
JG: That’s right, and so what’s happening now is that we will be about 6 or 7 minutes away in light travel time to Mars, and so everything’s gotta be done automatically. The whole entire lining sequence has to be done automatically.
NDT: So tell me what experiments are on this mission? Ranking in your favorite order of what this thing is going to do.
JG: Alright so the core, that’s important. There’s two instruments that help the core make the decision
NDT: By the way, I am not a geologist. I keep thinking what the rock is on the surface is probably the same a few inches in. But you’re telling me no, the rock could be completely different on the inside, is that what you’re telling me?
JG: Curiosity told us that. So the red Mars is there. And when we dug just below the surface, we saw gray Mars. An entirely different planet.
NDT: Oh! Because Mars is red from the iron oxides. Okay, got it.
JG: So indeed finding the right spot to core is important. And so the context instruments are Sherloc and Pixl, those are on the arm. And they’re going to be imaging and helping us decide where we’re going to go. In addition to that we have another instrument called RimFox from Norway, and it sits underneath the belly pan next to where the copter would be after we drop it. And it is a ground penetrating radar. It gives the stratigraphy. It gives an idea, this might be a good place to drill. That’s important! And then we have, right on the mast, right here at the top, a fabulous instrument called Supercam. It is designed to send out a laser, evaporate the rock, get a spectrum, and help us understand the composition of the rocks in front of us and then guide us to where we want to go.
NDT: You know Chuck, if martians are there on the surface and they see laser beams coming out of this, they’re going to think we’re declaring war.
CN: Exactly, we no longer come in peace.
NDT: We come here to vaporize you.
JG: They think we’re just heating up the place so they can bbq. But that might be a different story. Another instrument is Mastcam. And this one has a fabulous set of cameras that sit below Supercam and they are at about the height of my eyes, which since I’m 6’4”, they’re about 6’. So the stereo imaging we get is going to be just like a human walking around on the surface.
JG: And then we have an instrument called Moxie, this is the one that brings in the atmosphere, and zaps it. And so you take CO2 which is the predominant atmospheric composition, pop off an oxygen giving you carbon monoxide and oxygen. You vent the carbon monoxide and you understand how much oxygen you can get from the process. You do that during the morning, afternoon, and evening and throughout the year, and that gives us an efficiency factor. And that’s like Mark Wattman’s oxygenator.
NDT: If you go there you will have prior knowledge of how effectively you can pull oxygen out of the CO2 molecule.
JG: That’s right and that’s important to supplement whatever we take up there. And it may be the main way we acquire oxygen to use in a variety of purposes. Breathing of course is one of them. Adding hydrogen creates water. So oxygen is important. Gotta have it. There’s another instrument that is pretty special to me. Alright? And hardly anyone knows about it. As head of planetary when we were putting this together I said we absolutely have to have a-
CN: Sorry, I’m sorry. I took a guess. I went with cupholders. Say it again! What is it?
JG: Okay so, the new instrument that’s on it that I really like is a microphone. This allows us to hear the sounds of Mars.
JG: Now I don’t suspect at night when Perseverance is sitting there grunging away at stuff that we hear crickets! But we’re going to hear all kinds of sounds. As the rover moves, we can use it as an engineering perspective, because if you hear metal against metal you’re going to stop it right away, and figure out what’s happening. And so not only is it going to be fantastic to listen to the winds and the sounds of Mars, we’ll actually hear the sounds of the rover moving during the day and even at night.
CN: The coolest thing in the world would be if you heard this, “Are they gone yet?”
NDT: Right, right, right! Or “quick duck! The camera is turning this way. Get out of the way”. (laughs)
JG: I would like that. Let’s see if we can find that in the data.
NDT: The weird thing is not that you would hear them speaking, it’s that they’d be speaking English. That would be the total weird thing!
NDT: James we gotta call it quits here. Listen, good luck to you and the mission. And what’s not apparent in this interview, is that thousands of people work on these crafts. Alright, excellent. James, we’ll get back to you when the rover arrives at Mars safely! We’ll get you back on and get an update on how this has turned around.
JG: My pleasure, let’s do it.
NDT: Chuck! It was good to see you man.
CN: Always a pleasure to be here.
NDT: Alright this has been a special edition of Star Talk Explainer, getting the latest on our mission to Mars. As always, keep looking up, especially if you’re looking at Mars.