Europa, the ice-encrusted moon of Jupiter, is still everything it’s cracked up to be.
Juno, a NASA spacecraft that has been orbiting Jupiter since 2016, zipped within 219 miles of Europa’s surface early on Thursday, speeding by at more than 30,000 miles per hour.
Less than 12 hours later, the four images taken during the flyby, the closest observations of the moon since January 2000, were back on Earth.
“They’re stunning, actually,” said Candice J. Hansen-Koharcheck, a scientist at the Planetary Science Institute in Tucson, Ariz., who is responsible for the operation of the spacecraft’s primary camera, JunoCam.
In its news release, NASA highlighted one image centered on a region near the moon’s equator, Annwn Regio, showing long fractures that crisscross the bright, icy surface.
The alien landscape matches what was seen by earlier NASA visitors: the two Voyager spacecraft that flew through the Jovian system in 1979 and Galileo, which orbited Jupiter from 1995 to 2003.
The fractures pointed to the possibility of an ocean on Europa, hidden under the ice, creating the fractures through the stress of rising and falling tides. Other data, in particular magnetic field measurements indicating an electrically conducting layer like a salty ocean, convinced planetary scientists that an ocean indeed flows on Europa.
The presence of liquid water has made Europa a promising place to look for life elsewhere in the solar system.
The Juno flyby does not change the story.
“I would not say there was some feature that we were like, ‘Oh my God, that’s new,’” Dr. Hansen-Koharcheck said. Rather, the new images offer a better view of certain parts of the moon and help fill in details.
“We’re going to be able to tell the sort of geological history story better because you can link up different ridges and fault lines and get a more global or regional picture,” Dr. Hansen-Koharcheck said.
“I can’t say, ‘Oh, this one thing is just amazing,’” she said. Rather, there are many features that pique her interest. “It’s that kind of data. There’s so much complexity of Europa itself, and then these images really showcase that so nicely.”
All four images were available on Juno’s website. The originals have an orange-brownish hue, but the moon would look lighter-colored in reality. That’s because the camera was included on the space probe to bring in participation by the public and was not primarily intended as a scientific instrument. “We didn’t make the effort to do the white balancing,” Dr. Hansen-Koharcheck said. “It’s not deliberate by any means.”
People around the world immediately started downloading the images and enhancing them.
The pictures, as well as other data gathered by Juno, will help scientists planning Europa Clipper, a NASA mission that is to launch in 2024 and make repeated close flybys of Europa. It will also assist the Jupiter Icy Moons Explorer, or JUICE, a European Space Agency mission scheduled to launch next year that will study Europa and two other Jovian moons, Callisto and Ganymede.
Juno launched in 2011 and arrived at Jupiter, the solar system’s largest planet, in 2016. It made repeated dives close to Jupiter to allow its instruments to probe beneath the planet’s clouds. Those revealed never-seen-before lightning high in the atmosphere and the raining of ammonia-rich baseball-size conglomerations that the scientists nicknamed mushballs.
When the tasks of the primary mission were completed last year, NASA approved an extended mission for Juno, an additional 42 orbits of Jupiter that included close flybys of three of the large moons: Ganymede, Europa and Io.
Juno completed its Ganymede flyby in June 2021. It will get close-up looks at Io, the most volcanically active place in the solar system, in 2023 and 2024.