AILSA CHANG, HOST:
Ten years ago, engineers at NASA's Jet Propulsion Lab celebrated the successful landing of its fourth robot on Mars, the Curiosity rover.
(SOUNDBITE OF ARCHIVED RECORDING)
UNIDENTIFIED PERSON: Touchdown confirmed. We're safe on Mars.
CHANG: Its mission - to determine whether the planet's environment could have ever supported life.
(SOUNDBITE OF ARCHIVED RECORDING)
UNIDENTIFIED PERSON: Proud to see where our Curiosity will take us.
CHANG: Curiosity is about the size of a car. And it's decked out with scientific instruments used to study the planet's climate and geology. And 10 years later, scientists are happy to report the rover's mission has been a huge success. Here to tell us all about it and what we've learned is Dr. Ashwin Vasavada. He is the head scientist on the Curiosity team. Welcome to ALL THINGS CONSIDERED.
ASHWIN VASAVADA: Thank you so much - so wonderful to hear those memories from 10 years ago.
CHANG: I imagine. So I want to start with the big question that Curiosity was built to answer, and that was, was the planet Mars ever habitable?
VASAVADA: Yeah. You know, we didn't know whether that was the case before Curiosity landed. And now we have a resounding yes. It not only was habitable at one moment in time in Mars' history but probably habitable for millions or tens of millions of years.
CHANG: OK. So it was habitable, but, like, what kind of life forms are we talking about?
VASAVADA: So Curiosity can't detect signs of life, and we actually still don't know if Mars ever harbored life. You know, we've explored Mars enough to know that there are no dinosaur footprints, you know, and no big lifeforms around today. So if life ever did take hold, it probably never got beyond kind of a microbial stage.
CHANG: I see. And then what happened on the planet to make it not habitable anymore?
VASAVADA: When you look at ancient Mars from the satellites that we've had exploring Mars, you know, for decades now, you can see evidence that rivers once coursed along the surface, maybe even an ocean existed at one point. So early Mars, we're talking three or four billion years ago, was a much more Earthlike place than Mars is today. So at some point in time, the climate of Mars radically changed. It lost most of its water and most of its atmosphere and became a cold and inhospitable desert that it is today.
CHANG: Do we know why the climate of Mars radically changed?
VASAVADA: We believe it has to do - a lot of, with Mars' size, ultimately. It's a smaller planet than Earth. That allowed it to cool faster. Once it cooled faster, it lost its ability to generate a magnetic field. Once the magnetic field stopped, the atmosphere was stripped away by radiation in space that led to its inability to stay warm and have liquid water.
CHANG: So fascinating. OK. So Curiosity landed in an area called the Gale Crater, right? Can you tell us what is so special about that particular site?
VASAVADA: So Gale Crater is an impact crater formed when a big space rock hit the surface. But later on, it was filled by sediment that was deposited in lakes and formed layers of mud that built up over time into the size of a mountain.
CHANG: Wow.
VASAVADA: What this meant is that we could see if that sediment really was deposited within kind of liquid water environments like lakes and streams. We could read the early history of Mars by driving up these what are now rock layers and determining whether any of those periods of Mars' time had these habitable conditions.
CHANG: Well, as the head scientist on this team, I'm curious - for you personally, what has been the most exciting or maybe the most surprising part of your work?
VASAVADA: I think the most surprising result from Curiosity to me is just how long the habitable conditions lasted. We've now driven up over 2,000 vertical feet on the mountain. And for the most part, every layer we've looked at formed in a wet environment and had conditions that would have been favorable to life, which is really exciting.
CHANG: This has been such a cool conversation. Head scientist of the Curiosity rover, Dr. Ashwin Vasavada, thank you so much for joining us today and congrats on 10 years.
VASAVADA: Thank you very much. Yeah, it's been a blast. Transcript provided by NPR, Copyright NPR.
