Ocean worlds: If you could collect every drop of water on Europa and every drop of water on Earth into a single giant bead, and Europa's bead wins
Kevin Hand—JPL/Caltech), Jack Cook—Woods Hole Oceanographic Institution, Howard Perlman—USGS
By Jeffrey Kluger
June 22, 2016

For a planet that has absolutely no chance of harboring life, Jupiter gets a lot of love from Earth. Five NASA spacecraft have flown by or orbited it before and another orbiter, Juno, is set to arrive soon—on July 4, in fact.

Certainly, there are a lot of good reasons to study what is by far the largest planet in our solar system, even if looking for life is not one of them. Still, if Jupiter itself is a biological no-go, Jupiter’s little moon Europa might be a whole different matter, with the smart money betting that if we ever do find life elsewhere in our solar system, it’ll be the Europans who show their faces (or fins or membranes) first.

Now, it appears, NASA is finally going to go take a look. Thanks to an aggressive push in Congress (you read that right: Congress), a pair of missions to the mysterious moon may be launching as early as 2022 and 2024.

The case for life on Europa is a strong one. Even seen through Earth-based telescopes, the moon appeared to be covered in a bright white shell of water ice. Spacecraft confirmed that hunch and, tantalizingly, found that that crust is regularly fractured and resurfaced, a sure sign that there is a deep—perhaps very deep—ocean of liquid water underneath.

That makes sense. Gravitational flexing from Jupiter as well as from Europa’s sister moons generate a lot of internal heat, which would melt the ice everywhere but the surface. The resulting global ocean may be as much as 90 miles (150 km) deep, and the ice as little as 6 miles (10 km) thick. (The deepest spot in any Earthly ocean, by contrast, is just 6.8 miles [11 km], meaning that Earth, which is four times the diameter of Europa, actually harbors less water.) What’s more, rusty colored stains on the ice around the cracks suggest that the water is heavy in salts and minerals. Chemistry plus energy plus time—all of which Europa has in the right mix—may be all that is necessary to cook up life.

For more than 20 years, NASA has been contemplating a mission to Europa, and for much of that time, Texas Congressman John Culberson—a self-described amateur astronomer, whose district includes portions of Houston—has been trying to secure the funding for it. His perch on the appropriations committee has put him in a good position to accomplish that, and a dozen years ago he did succeed in getting the money and the mission written into NASA’s budget. But he was a newbie Congressman at the time and had a lot to learn.

“I agreed to serve on appropriations so I could help NASA and the sciences,” he says. “I included language in a committee report that NASA would fund and fly this mission to Europa. But as a new member of the committee, I did not understand how to draft it correctly and protect it.” The result: NASA was allocated the money but when things got tight—as they always do for an agency that has to fight so hard for funding—it was able to cannibalize the Europa appropriation for other more pressing projects.

This time around, Culberson closed that option. A portion of the Congressional spending provisions signed into law in December 2015 includes $260 million for a Europa orbiter set to launch “no later than 2022” and a lander “no later than 2024”. And the relevant auxiliary verb included in the statute is “shall”, as in NASA shall fly the specified missions by the specified dates.

“Today the Europa orbiter and lander is the only mission it is illegal for NASA not to fly,” Culberson says, with no small amount of parliamentary pride.

Of course, writing airtight legislation is easier than designing and building the called-for hardware, and NASA has a way to go before its Europa spacecraft are actually ready to fly. The orbiter, which would be the easier of the two ships, would circle Europa for two years looking for the best spots for a lander to touch down—preferably near a fracture in the ice which is emitting frosty geysers from the oceans. That would make it easy to sample the water as it fell back to the surface in a sort of Europan snow.

The ultimate goal, though, would be to peer directly into the calmer waters of the ocean and perhaps even go swimming. The lander will thus be equipped with a drill that includes a heater, to soften the ice, and a pair of counter-rotating blades—essentially two stacked blades, one of which rotates clockwise, the other counterclockwise.

“That neutralizes the centrifugal force and the gyroscopic effects,” says Culberson. “It also produces a huge rooster tail of sample material.” Once a hole was drilled, a semi-autonomous submersible could dive in and begin investigating, sending its data back to the lander on the surface, which would relay it to the orbiter, which would in turn send it back to Earth.

It’s a complex system, but well within existing technological capabilities. The real rub is something else that’s written into the Congressional legislation: the requirement that NASA “shall use the Space Launch System as the launch vehicle…” The Space Launch System, or SLS, is the prosaically named heavy-lift booster NASA is building that is envisioned as the sort of grandchild of the Saturn V moon rocket. It’s a sweet machine and could do the job, but the space agency has been working on it in one way or another since 2004 and its next test flight is not even planned until September 2018.

If the SLS does get off the ground, it could dramatically cut the travel time to Jupiter, from six years to just two. That’s because the rocket has the power to fling the spacecraft on a more or less direct route to Jupiter rather than a spiraling trajectory that sends it swinging past the solar system’s inner planets for multiple gravity boosts.

“SLS is on track, on target and on schedule,” Culberson says. Maybe, but SLS has been on track, on target and on schedule many times in the past decade—and then it wasn’t.

The reality is, NASA engineers may or may not be able to meet Congress’s target dates; being legally required to try doesn’t mean anyone’s going to jail if they don’t succeed. Still, deadlines can be bracing, and for bureaucracies, highly motivating. Europa, meantime, presents no such time pressures. It’s been there for 4.5 billion years; it’ll still be there whenever we’re ready to visit.


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