Europa, a moon of Jupiter, is one of the most fascinating places in the solar system. A little smaller than Earth's moon, Europa is has subsurface water where—just maybe—life could exist.
The problem is that the moon gets bombarded by radiation from its parent planet, which would be harmful to any potential life there. But a new study suggests that, at least in some places, a Europa lander wouldn't need to look too far.
The new study, produced by NASA's JPL and Johns Hopkins, comprehensively mapped how radiation from Jupiter hits the moon. Tom Nordheim, a research scientist at JPL, says in a :
"If we want to understand what's going on at the surface of Europa and how that links to the ocean underneath, we need to understand the radiation. When we examine materials that have come up from the subsurface, what are we looking at? Does this tell us what is in the ocean, or is this what happened to the materials after they have been radiated?"
The team relied on data from missions like Galileo, which conducted flybys of Europa two decades ago, and even the electron measurements from NASA's Voyager 1 spacecraft, which flew near the moon in 1979. The radiation varies by location, but in general the team found that it hits hardest close to Europa's equator, and lowest at the poles. That's similar to the . The harshest radiation zones look like ovals on Europa, taking up around half of the moon's surface.
Nordheim and his team looked beyond two dimensions to get a sense of how deep the radiation goes. That sense of depth would show how far a Europa lander would have to dig to get a sense of readings for amino acids, the building blocks of life.
While the moon's radiation zones are wide, they're also shallow. At the highest radiation zones, it goes 4 to 8 inches (10 to 20 centimeters) deep. Closer to the poles, it gets as shallow as less than 0.4 inches (1 centimeter).
"The radiation that bombards Europa's surface leaves a fingerprint. If we know what that fingerprint looks like, we can better understand the nature of any organics and possible biosignatures that might be detected with future missions, be they spacecraft that fly by or land on Europa," says Kevin Hand, a co-author of the new research.
If NASA has its way, that future mission will be the , which could launch as early as 2022. Sending a probe as far as Europa and landing there would be a tremendous technical achievement. Last year, NASA completed what's known as Phase A, a review of potential instruments needed for such a mission. Next comes Phase B, where vendors are selected for the instruments and prototypes begin to take shape.
It's a long process. But when sending something to Europa, 390 million miles away from Earth, there's only one chance to get it right.