The mission’s biggest lingering question is how exactly it will reach its target. Europa Clipper could arrive around Jupiter anywhere 2.5 to 6 years after launch, depending on which rocket the mission relies on.
When the U.S. Congress was debating Europa Clipper, legislators secured key votes to approve funding by requiring the spacecraft fly atop NASA’s long-delayed and much-maligned Space Launch System. The rocket is being built in Alabama, where it provides jobs for the constituents of certain senators and members of congress. But after years of delays, it’s still never flown. NASA itself has suggested not using the rocket because it’s massively more expensive than other options, like SpaceX’s Falcon Heavy and United Launch Alliance’s Delta IV rockets.
Plus, Europa Clipper has already had to make cost cutting decisions due to budget overruns, as reported by the website SpaceNews. So, ultimately, getting Europa Clipper off the ground on schedule and on budget could require new legislation.
Laying the groundwork for a Europa lander
Europa Clipper’s launch vehicle wasn’t the only choice that congress mandated by law, either. The space agency also is required to later send a lander to Europa, something it’s so far been reluctant to commit to.
“NASA’s a big bureaucracy. It's difficult to get them to move or do things, so it was necessary for me to write it into law,” former Congressman John Culberson of Texas told Astronomy in 2015. “In fact, [this] is the only mission that it is illegal for NASA not to fly. And I made certain of that.”
Undoubtedly, Europa’s underground ocean is its most interesting feature. And if there’s life on the world, it’s likely beneath the surface. But getting down there will not be easy. In the past, scientists have suggested landing probes on the surface that could melt through miles of ice and deploy submarines to explore the vast oceans.
Sending a lander would be expensive and technologically challenging, however. And more importantly, though NASA makes valiant efforts to avoid it, the spacecraft could carry earthly lifeforms with it, compromising any data and possibly bringing invasive microbes to a pristine alien environment.
That’s part of the reason why, despite the legal requirement, NASA has yet to formalize a plan to build a Europa lander. However, the scientific community has since proposed a number of potential options to explore Europa’s surface — as well its ocean below.
In the meantime, Europa Clipper will rely on other ways to measure the composition of the moon's water and note places where it interacts with the surface. And that work should pave the way for the future of exploration. Once astronomers better understand the internal workings of the icy moon Europa, they’ll be able to choose the best place to take a peek inside and search for signs of life.
“Why would we go all that way and not answer the single most important question: Is there life on another world?” Culberson said. “Well, the only way you answer it is with a lander, and that’s the consensus of the scientific community. I’m convinced they’re right.”