NASA announced yesterday that it has selected nine science instruments for a spacecraft it plans to send to Europa sometime in the 2020s. The Jovian moon is believed to have a liquid ocean—a key ingredient for life—beneath its icy crust.
“We’re trying to understand the potential habitability of Europa,” said Robert Pappalardo, Pre-Project Scientist for the proposed Europa Clipper. “That’s the big picture.” The Clipper is currently the leading concept for a Europa mission, though it has not yet received formal approval from the space agency.
“ALL THESE WORLDS ARE YOURS EXCEPT EUROPA,” a superior extraterrestrial intelligence welcomed/warned humanity back in the 1984 movie 2010: The Year We Make Contact. “ATTEMPT NO LANDING THERE.”
That’s fine; nobody’s talking about landing, at least not yet. The Clipper proposal would send a solar-powered spacecraft into a looping orbit of Jupiter that would include at least 45 flybys of Europa and would bring it as close as 16 miles to the surface to collect imagery and data.
NASA evaluated 33 proposals for instruments to be sent to Europa and selected nine, including high resolution cameras, two spectrometers, a magnetometer, and an ice-penetrating radar system. Following up on the Hubble Space Telescope’s observation of water vapor over Europa’s south pole in 2012, which suggest possible water plumes, a thermal device will try to confirm their existence by looking for “hot” sites on the surface.
A complete list of the instruments selected and their designers and attendant acronyms appears here.
As Pappalardo and Clipper Pre-Project Manager Barry Goldstein (the “Pre-” will drop from their titles if/when Clipper becomes NASA’s official Europa mission) explained to me in Goldstein’s office at the Jet Propulsion Laboratory in Pasadena, California, last month, the Clipper’s mission design is a triumph of parsimony. An earlier, canceled Europa Orbiter proposal would have needed a large amount of propellant to slow itself into Europa orbit. So the team decided on multiple flybys instead.
There are even advantages to the new approach. Goldstein said the flyby solution “allows us to trade propellant for aluminum” to shield spacecraft electronics from the punishing radiation of Jupiter’s magnetosphere. “In orbit around Europa, you’re dying and you’re dying quickly.”
The Clipper will fly by the icy moon at fortnightly intervals on average, using its abundant non-observational time to transmit the data collected on each flyby back to Earth. That wide orbit will also place the Clipper out of the intense radiation zone for long stretches, extending the operational life of its instruments.
If the Clipper team gets formal approval and the roughly $2 billion they need in funding, the mission could launch as soon as June 2022. Less money will mean a later launch, Goldstein said. Planetary alignment provides a new launch window every 13 months.
How quickly the Clipper reaches Europa will depend on what kind of a ride it hitches. If, as Goldstein and Pappalardo hope, it travels via the still-in-development Space Launch Vehicle, it could get to Jupiter in a little over 2.5 years. If it goes via a less powerful rocket, the travel time would vary, depending on its trajectory, from between roughly 4.5 and 7.5 years, with another year after its arrival at Jupiter before Europa flybys could begin.