RAY SUAREZ: After traveling more than 400 million miles from Earth, yesterday NASA’s mars Phoenix lander entered the red planet’s atmosphere and, following a hazardous descent, softly touched down on Mars’ northern polar region.
NASA CONTROLLER: Touchdown signal detected.
RAY SUAREZ: The safe landing was met with cheers by mission managers at the NASA Jet Propulsion Laboratory in California.
The probe immediately got to work, sending back the first-ever images of the planet’s northern arctic landscape. The 900-pound solar-powered Lander will spend the next three months studying soil and ice using a robotic arm and other instruments in the hope of finding out if Mars could have supported life sometime in the past.
Here to tell us more about the mission is Raymond Arvidson, a professor of earth and planetary sciences at Washington University in St. Louis. He’s been involved in NASA’s Mars projects since Viking in 1976 and led the science team that selected the landing site for the current Phoenix mission. And he joins us from Tucson.
And, professor, what’s the difference between Phoenix and the rovers that were launched earlier in the decade? How does it advance that science?
RAYMOND ARVIDSON, Washington University in St. Louis: Well, the two rovers — Spirit and Opportunity — that landed in January 2004, you know, they were supposed to last 90 days. They’re going on four-and-a-half years, so they’re way out of warranty, but still discovering a lot.
Those are equatorial-zone measurements. And the vehicles were moving, roving, and looking at the ancient rocks. And both Spirit and Opportunity have found evidence for very old rocks that formed in the presence of water. So that’s very important, in terms of ancient conditions and inhabitability.
Phoenix is different. Phoenix doesn’t need lateral roving capability. It needs to go down maybe 50 centimeters into the soil and ice. And it has vertical mobility.
We’re going to a much younger terrain, and we’re going to do the first actual touching and sampling of water ice and looking at the chemistry and, presumably, the information that will tell us whether or not this zone was habitable in the past, whether or not liquid water existed.
New Martian photos
RAY SUAREZ: Well, the first photos that came back from the Martian polar surface to the untrained eye don't look very remarkable, but if you know what you're looking at, what's interesting? What's worthy of pointing out about these photos of the surface?
RAYMOND ARVIDSON: Oh, my gosh. I'm still on an adrenaline high from looking at the images last night, you know, the sol-zero images (ph).
What we see is that the terrain of Mars has been shaped over a few meters and it forms what's called patterned ground. And that's indicative of very, very strong, icy soil that's been through a very cold period in the winter and it's fractured into these cracks.
And water may have filled in the cracks or sand and dust may have filled in the cracks. And then, in the summer, when it warmed up and expanded, the cracks were already filled with something, so the polygons just popped up.
That's, again, indicating that we landed in the right spot, if we want to sample soil and if we want to sample soil in contact with ice and analyze all that material and look for the evidence that we're looking for, that some of that ice may have been liquid water in the past. If we find evidence for liquid water, it really increases the probability that this was a habitable zone.
RAY SUAREZ: Well, let's talk a little bit more about the "how." You've mentioned testing these soils and digging a little bit under the surface. Once the lander gets a scoop of Martian matter, how does it figure out what's worth knowing and what needs to be known about that scoop full of stuff?
RAYMOND ARVIDSON: There will be, let's see, 12 scoopfuls that we'll analyze, actually more.
So one area is to take soil and to put it into a little chamber. And we actually brought our own water from Earth, which is ice now, but we'll melt it and put it in the chamber. And we'll look for salts that are dissolved, like table salt and more complex salts, like sulfate.
Those pieces of information would tell us that water migrated through the soil, evaporated, or sublimated directly from ice to vapor, and then left behind that signal. It's evidence for liquid water.
Another thing we'll do is take the soil and the icy soil and put it into a set of ovens. And we'll heat up the soil and the icy soil and look for compounds based on the temperatures that are given off as we heat that material up. We'll also take the gasses. And those will be streamed into what's called a mass spectrometer.
And the mass spectrometer will be used with data to tell whether or not there are organic molecules present. And, also, the detailed make-up of the gases tells you about the climatic history.
So we're after kind of understanding that whole niche and the modern climate, the ancient climate, and whether or not there are organic molecules, but certainly the history of that ice and whether or not it ever was in a liquid form.
Summer of science ahead
RAY SUAREZ: So loading up the scoop, heating some of the substances, are these things that the lander already knows how to do or is there somebody at the controls back on Earth?
RAYMOND ARVIDSON: Well, the lander can do what it's told. And we have, for the first week, it's called a characterization phase. What we're doing -- in fact, the shift begins in about two hours, because we work on Mars time. What we're doing is turning on the instruments, validating them, getting them ready to go.
And then, over Earth's summer, through August, we'll be sending commands up each day that will tell the robotic arm exactly where to scoop the soil, exactly where to drill in to get the ice with our little rasp, and then how to get that back into the chambers on the spacecraft to do the analysis.
So we're set up. But it requires humans in the whole process to make sure it's all done correctly.
RAY SUAREZ: And very quickly, before we go, when you say you send a command, how long does it take to get there, 400 million miles?
RAYMOND ARVIDSON: Oh, 15 minutes. It takes 15 minutes. So the way it operates is we send the commands up to the spacecraft when the spacecraft wakes up in its morning in the northern hemisphere. The spacecraft does what it's supposed to do, and it relays the data back, just before it goes to sleep in late afternoon.
RAY SUAREZ: Professor Arvidson, thanks a lot.
RAYMOND ARVIDSON: Thank you.