MARY LOUISE KELLY, HOST:
An alien ship landed on Mars today. In this case, the aliens would be us.
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UNIDENTIFIED PERSON: Touchdown confirmed. InSight is on the surface of Mars.
UNIDENTIFIED CROWD: (Cheering).
KELLY: A NASA probe called InSight touched down shortly before 3 Eastern this afternoon. NPR's Joe Palca is at the Jet Propulsion Laboratory in Pasadena, Calif. That is where InSight Mission Control is located. Hey, Joe.
JOE PALCA, BYLINE: Hi there.
KELLY: So big whoop went up there where you are. What was that like?
PALCA: Yeah. I'm actually across a courtyard from the control room, and I could almost hear it from here. It's pretty amazing.
KELLY: Yeah.
PALCA: Yeah. This was...
KELLY: So this went to plan? The landing went - it was smooth?
PALCA: Unbelievable. I mean, you know, if you'd written it out - it's just like a show, Mary Louise. You know, you set up all the milestones and posts, and they hit every single one. It was astonishing.
I mean, there were 6 1/2 minutes where this thing had to go from 12,300 miles an hour to 0. And it had to - it had to do that in 6 1/2 minutes.
KELLY: Oh, wow.
PALCA: So that involved - they call it the 6 1/2 minutes of terror, or seven minutes of terror. But it was, you know, a nail-biter for everybody involved because first the heat shield slows it down. Then, when it gets slow enough, a parachute comes into play. And after that, the parachute drops away. The radar comes on. It detects the ground. The 12 rocket engines come on. It comes slowly down, and it landed. And you heard it. It was amazing.
KELLY: Yeah, yeah. And there were - meanwhile, I should inject, there were two small spacecraft that were along for the ride, accompanying InSight. What are they there to do?
PALCA: Yeah. I think this was really cool. So there are two spacecraft the size of a large briefcase, essentially. And their job was to relay telemetry from InSight, the lander, back to Earth. And they did it perfectly. And it's amazing. These two little, bitty experimental satellites let people in Mission Control know exactly what was happening every second of the descent.
KELLY: It's just amazing to travel - I mean, I don't even know how many miles we're talking about.
PALCA: Three-hundred million miles, Mary Louise.
KELLY: I knew you would know, so I thought I'd drop that in there for you. OK, so...
PALCA: Three-hundred-one, if you want to get - if you want to get specific.
KELLY: (Laughter) Thank you. So the plan - the great, big plan for this probe is it's not going to look at the surface. It's going to look inside of Mars. Why?
PALCA: Right.
KELLY: What's it looking for?
PALCA: Well, there's, you know - there's a lot of lack of clarity about why you have rocky planets, like Earth, that turned out to be reasonably habitable. I mean, you know, we tend to like it here. And then there are rocky planets like Mars and Venus and Mercury that are not habitable. And the question is why?
KELLY: Yeah.
PALCA: And some of that answer may come from the ability of the core of the planet to generate a magnetic field. And so what this spacecraft, InSight, is going to do - or now it's called a probe, I guess, because it's not in space anymore - it's going to be listening for marsquakes, which are the Martian, of course, equivalent of earthquakes.
And if you study the signals that come - the shape of the waves that come from marsquakes, you can infer things about the interior of the planet.
KELLY: How long until we might get some results and know what it is learning?
PALCA: Well, actually, it's going to be awhile because even though it landed and the first pictures came back, they're going to sit on the surface for a while and just look around because they have a couple of instruments - one of them is this seismometer, which is the one that's going to measure the marsquakes, and they've got to pick the exact spot that they want to put that down. And so they're going to be looking around. And at some point, a robotic arm will drop it onto the surface.
And then there's another instrument that's going to be pounded into the ground - 16 feet into the ground - and it's going to take temperature measurements of the heat flux - the heat coming up from the planet. And so all that's going to take a few weeks to be deployed. And then it's going to take a while to gather in the data...
KELLY: Right.
PALCA: ...That these instruments are providing.
KELLY: All righty. Thank you, Joe.
PALCA: You're welcome.
KELLY: NPR's Joe Palca having quite the day there at NASA's Jet Propulsion Laboratory in Pasadena, Calif.
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