DAVID GREENE, HOST:
Later today, an 800-pound probe is scheduled to touch down gently on the surface of Mars. NASA's InSight mission left Earth last spring. The goal of this mission is to understand more about the interior of Mars. And NPR's Joe Palca is going to be at NASA's Jet Propulsion Laboratory here in Southern California for the landing. Right now he joins us from Pasadena.
Good morning, Joe.
JOE PALCA, BYLINE: Good morning, David.
GREENE: All right, so what's the latest on this mission here?
PALCA: Well, the latest seems to be that yesterday afternoon, there was a tiny course correction. Now, this probe has traveled more than 300 million miles. And it was about 11 miles off target, which I'd say is pretty good.
GREENE: That's not bad.
PALCA: But - no, it's not bad, but not good enough for NASA. So they had one tiny burst of the engine. They called it, actually, a burp. And now they're estimating, after tracking the probe and its consequences of this rocket firing, they think they're about a mile or 2 away from the target. So pretty close.
GREENE: Well, I just learned something from you - that burp is a space term. That's very cool.
GREENE: So make a distinction for me. This is not a rover mission, right? I mean, that's something we often hear about.
PALCA: No. Once this puppy lands, it's staying put. It's not going anywhere.
GREENE: OK, so it lands on the surface of this planet. And as I mentioned, the goal is to study the interior of Mars. What are we actually talking about?
PALCA: Well, yeah, it's kind of - I think it's kind of strange that you have a thing sitting on the surface, yet it's going to tell you all about the interior of Mars. But here's the deal. It has onboard very sensitive seismometers. And in Southern California, I'm sure you know what a seismometer is. It's a device for measuring earthquakes, right?
GREENE: Earthquakes, yeah, right.
PALCA: Only these are going to measure marsquakes (ph), which...
PALCA: ...Are the equivalent of earthquakes. And the thing is that you can tell, from the shape of the waves that these quakes generate, what kind of rocks or what kind of materials they're going through and something about the core of the planet and the interior structure of the planet. And so, literally, this mission looks into the planet, whereas all the other missions have pretty much scratched the surface, as it were. So that's the big difference here.
GREENE: So they're learning, potentially, a lot about this planet which could be really important. So when is this actually - landing actually set for? When is this all going to happen?
PALCA: So it's 11:57 Pacific time this morning. And before it lands, it has to go through this 6 1/2 minutes of a tortuous landing sequence. It comes in. It has a heat shield that's going to take off most of the speed, then a parachute that opens up when it's still going supersonic. Then 12 small rockets will combine.
And the whole process takes about six 6 1/2 minutes. And it goes from 12,300 miles an hour when it hits the top of the atmosphere to 5 miles an hour, and then it drops the - last few feet at 5 miles per hour, but, you know, that's not so bad. It's not going to break anything.
GREENE: This sounds really dramatic though. I mean, is there going to be a moment when you'll actually be able to report that this thing is safely there and beginning its work?
PALCA: Well, yeah, I mean, in fact - well there's a couple of ways. One is that about seven minutes, they say, after it lands, it will send out a tone that says, I'm here; all is well, you know, I'll check back with you later. But there is something interesting on this mission that they've never had before. When InSight launched back in May, it - the rocket also carried two small spacecraft called CubeSats.
And these CubeSats were designed to relay the telemetry from InSight back to Earth. So they're going to fly over as InSight is landing. And it's possible that we'll get, you know, like, moment-to-moment updates on how the craft is doing.
GREENE: Awesome stuff. NPR's Joe Palca. Joe, thanks a lot.
PALCA: You're welcome. Transcript provided by NPR, Copyright NPR.