GUY RAZ, HOST:
Now, one of the things the rover will be looking for are organic molecules that could at least indicate whether there was once life on Mars. But if searching for life in outer space is the goal, many scientists now say we might have better luck elsewhere, specifically one of Saturn's moons called Enceladus. NASA planetary scientist Chris McKay is working on a proposal to send a mission to Enceladus, which is more or less a frozen rock.
CHRIS MCKAY: Think of it as a small world or a large snowball. It's only a couple hundred miles in diameter, but it's particularly interesting because there's a geyser coming out of the south pole of Enceladus.
RAZ: Why is Enceladus so potentially exciting?
MCKAY: It's really exciting because of this jet of water. It's originating from what we're pretty sure is a subsurface liquid - sea or a lake, if you will. And most exciting to me that jet has in it, in addition to water, organic compounds that make up life.
RAZ: So if we are looking for life out there, what you're suggesting is that we should be headed towards Enceladus.
MCKAY: That's right. Of all the places in our solar system, it's the only place I know of where right now we can check all the boxes for habitability - water, energy, carbon, nitrogen - check, check, check, check.
RAZ: So, why the focus on Mars?
MCKAY: It was the first world we knew of where there was water or had been water other than the Earth. So Mars is still special, but it's in a category by itself because it's a place that humans want to go to.
RAZ: So, say, we wanted to send a spacecraft to Enceladus to, you know, to dig around a little bit, to check it out. How long would it take to get there?
MCKAY: Well, it's quite a long trip. It's seven years.
RAZ: Seven years.
MCKAY: That's how long the Cassini spacecraft took to fly to Saturn, and the data we have on Enceladus came from Cassini. Seven years is the trip time.
RAZ: And if we wanted to actually examine the material, I guess it would take 14 years, right, because it has to go there for seven years, spend a couple weeks there, and then seven years coming back.
MCKAY: That's right. And it's probably a year there orbiting Saturn, collecting the material, scooping up stuff. The only easy part of the whole mission is that the geyser is coming out in space and we just fly through it and collect our samples. It's almost like there's a big sign on Enceladus that says free samples, take one.
RAZ: What would Enceladus look like if we landed a craft there?
MCKAY: It would look like a big, huge field of ice. So Enceladus is not the fascinating geological world that Mars is. What's really interesting about Enceladus is only the fact that underneath that ice, there's a lake. And in that lake, we know there is an energy source and there's organic material. So Enceladus is sort of a one-trick pony, but if you're just interested in the search for life, then Enceladus has got to be number one on my list.
RAZ: Number one on your list.
MCKAY: That's right. I was once asked if I had a little scooter like the Millennium Falcon I could go anywhere in the solar system, where would I go? Where would I punch in first? Enceladus. Fly to that plume.
RAZ: If we eventually did get a craft on Enceladus and we did discover that there is life there, what do you think that life would look like?
MCKAY: Well, that to me is the important question. If we find that there's life on Enceladus and if that life is different than Earth life, then that's fascinating. That allows us for the first time to see what other ways there are to do life besides the DNA for all life on earth. What about possibilities? It could be as simple as Earth-life, or it could be so different that we can't even recognize it.
RAZ: That's Chris McKay. He's a planetary scientist for NASA. He's finalizing a proposal to start a new discovery mission to Saturn's moon, Enceladus. Chris McKay, thanks so much.
MCKAY: Thank you.
RAZ: And you're listening to ALL THINGS CONSIDERED from NPR News. Transcript provided by NPR, Copyright National Public Radio.