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One of the things the Mars rover will look for is organic molecules that could at least indicate whether there was once life on the Red Planet. 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, 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 that's not much more than 300 miles in diameter.
"Think of it as a small world or a large snowball," McKay tells Guy Raz, host of weekends on All Things Considered.
But this large snowball is interesting to scientists such as McKay because there's a geyser coming out of its south pole from what scientists believe is a subsurface body of liquid water, like a sea or a lake, which contains organic compounds.
It's McKay's job to look for life forms beyond Earth, and the discovery of organic compounds is a crucial piece to that puzzle.
"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," he says, "water, energy, carbon, nitrogen — check, check, check, check."
So why all the focus on Mars?
McKay says Mars holds a special place in space exploration because humans may actually visit and examine that planet. It was the first world where scientists discovered there was once water. It's also appealing for possible biological and geological findings that can be discovered on Mars' surface.
At this point, it would be practically impossible to land on Enceladus. But McKay says, even if it were possible, it wouldn't exactly be a scenic site — more like a huge field of ice. But Enceladus tops his list for the search for life.
He was once asked, "If I had a little scooter like the Millennium Falcon, and I could go anywhere in the solar system, where would I go, what would I punch in first?"
His reply: "Enceladus."
McKay is putting together a proposal for NASA to send a mission to the moon. The most recent findings come from the Cassini spacecraft that's orbiting Saturn.
McKay estimates any mission would need at least 15 years to travel there, collect samples and return.
The only easy part about exploring the possibility of life on Enceladus is that the geyser is erupting water into space. So once there, it would be fairly easy to collect samples.
"It's almost like there's a big sign on Enceladus, it says 'Free samples, take one,'" McKay says.
What continues to motivate McKay to push for a NASA mission on Enceladus is the possibility of life, especially if that life turns out to be different from life on Earth. He says that would allow humans, for the first time, to see what other ways life could be configured besides the DNA-based coding of life on Earth.
"It could be as simple as Earth-life — or it could be so different that we can't even recognize it," he says.