Europa Clipper, NASA's mission to Jupiter's oceanic moon, set for launch

Europa Clipper, NASA's mission to Jupiter's oceanic moon, set for launch

TO Mikhail Greshko & Nature Magazine

After decades of dreaming about Jupiter's moon Europa – and the vast ocean that likely lies beneath its icy surface – scientists are now weeks away from sending a spacecraft there. NASA confirmed yesterday that the Europa Clipper mission will launch as scheduled, following concerns that it could be significantly delayed by possible faulty transistors installed on the US$5 billion spacecraft.

“We are confident that our beautiful spacecraft and its experienced crew are ready for launch and a full science mission to Europa,” Lori Leshin, director of NASA's Jet Propulsion Laboratory (JPL) in Pasadena, California, said at a press conference Sept. 9.

At more than 3.2 tons, about 5 meters tall and more than 30 meters wide with its solar panels fully deployed, Europa Clipper is the largest spacecraft NASA has ever built for a planetary mission. Yesterday, the mission passed what NASA calls a “key decision point E” — the final checkpoint that must be cleared before launch. The spacecraft’s launch window opens October 10.

On support for scientific journalism

If you enjoyed this article, please consider supporting our award-winning journalism: subscriptionBy purchasing a subscription, you help ensure a future of powerful stories about the discoveries and ideas shaping our world today.

If it launches successfully next month, the orbiter will arrive at Jupiter in April 2030. Its nine instruments will then probe both Europa’s icy crust and the ocean that scientists suspect lies beneath it to determine whether the moon could support life as we know it. Previous missions have suggested that Europa’s icy surface hides an underground ocean of saltwater twice the volume of water in Earth’s oceans. The moon’s fractured, apparently young surface also implies that the moon has active geology — hinting that Europa’s interior could be warm and dynamic enough to support the complex chemistry of life.

“There’s no such thing as a tricorder — a fictional tool from the Star Trek universe — that we can point at something to see if it’s alive,” said Kurt Niebur, the Europa Clipper program scientist at NASA Headquarters in Washington, D.C., during a news conference. “It’s extremely difficult to detect life, especially from orbit,” he said. “First, we ask a simple question: Are the ingredients for life there?”

Turbulent Waters on the Way to the Ocean World

Before the transistor panic, Europa Clipper had its share of setbacks. In 2019, NASA angers scientists by cutting sophisticated magnetometer from spacecraftciting budget concerns. The mission has also been beset by years of uncertainty about how it would get to space. That’s because the U.S. Congress has long ruled that the spacecraft must fly aboard NASA’s long-delayed Space Launch System rocket. Finally, in 2020, U.S. lawmakers cleared the program to select the reliable Falcon Heavy rocket from private company SpaceX in Brownsville, Texas, for the launch.

Possible transistor problem raised its head in May of this year when NASA engineers learned that batches of a certain type of transistor already installed on the Europa Clipper spacecraft were not behaving correctly. The components, called MOSFETs (metal-oxide-semiconductor field-effect transistors), act as switches in electrical circuits. They came from a NASA supplier, Infineon, based in Neubiberg, Germany.

Because Europa Clipper must fly by Europa 49 times at a distance of just 25 kilometers (15 miles), the spacecraft will also have to pass through a barrage of charged particles accelerated by Jupiter's magnetic field, which is about 20,000 times stronger than Earth's. That means the electronics housed in the orbiter must be resistant to radiation damage.

But in May, NASA said it was investigating whether there was a risk of failure of the mission’s transistors. The agency began four months of intensive 24-hour tests at three different facilities: JPL; Johns Hopkins Applied Physics Laboratory in Laurel, Maryland; and NASA’s Goddard Space Flight Center in Greenbelt, Maryland. “It was a huge lift, and I think ‘huge lift’ is a huge understatement,” Leshin said.

After evaluating spare MOSFETs from the same batches that were installed on Europa Clipper, NASA found that the spacecraft's circuits would perform as expected. This conclusion is based in part on the fact that during the first half of its four-year baseline mission in Jupiter's orbit, the spacecraft will be exposed to the worst of Jupiter's radiation only one day out of every 21 days. The rest of the time, the orbiter's transistors can partially self-heal from radiation damage with gentle heating through a process called annealing.

“While Europa Clipper does get immersed in a radiation environment, once it gets out, it gets out long enough that those transistors have a chance to heal and partially recover between flybys,” said Jordan Evans, Europa Clipper project manager at JPL, during the conference. “We can — I’m very confident, and the data supports it — complete the original mission.”

This article is reproduced with permission and was first published September 10, 2024.