Data collected by NASA's Galileo spacecraft in 1997 was put through new and advanced computer model to untangle a mystery - a brief, localised bend in the magnetic field - that had gone unexplained until now. During this trip, the spacecraft swung by Europa 11 times, conducting radio experiments that hint of an atmosphere.
Twice before has Nasa reported evidence, from its Hubble Space Telescope, for the existence of water plumes on Europa, though this interpretation has caused much debate. Observations of plumes were made by Hubble in 2012 and 2016. The 1997 flyby was close to the site of the repeat detection by Hubble.
Jupiter's moon Europa is one candidate. But the data didn't match that signature for this flyby. In the sequence of numbers produced by those two instruments, they immediately spotted something unusual: Anomalous blips, lasting about three minutes, centred around Galileo's closest approach to the moon. Jia, however, had worked with Galileo's data when he was a graduate student, so he had a good sense for the kind of data the probe typically collected.
Jia said, "One of the locations she mentioned rang a bell".
"That's the moment where we realized that we might have something in the old Galileo data that we never paid much attention to", Jia says. In both cases, the data indicate plumes erupted from roughly the same region, a known thermal "hot spot" on the moon's surface. For starters, Jia said, the Galileo mission team wasn't specifically looking for plumes. "It's unbelievable how hard it is to anticipate something that just hasn't happened before", she said. This new analysis adds backing to theories that an ocean of liquid salt water exists below the ice.
Unlike on Earth, however, this ocean is deep enough to cover the whole surface of Europa, and being far from the sun, the ocean surface is globally frozen over. There, microbes don't receive energy from sunlight but use methanogenesis, a process that reduces carbon dioxide with hydrogen, to form methane.
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As Swerdlove and another officer grappled with Campbell, she said that if Swerdlove took his hands off of her, she would get out. The woman refused to sign her ticket, which is against the law in Georgia, and was told she would be arrested for not complying.
Europa has always been thought to cover a salty ocean about twice the size of our planet's. "It's unlikely that one of these plumes is going to throw a fish into space that's going to whack into Europa Clipper", Cynthia Phillips of NASA's Jet Propulsion Laboratory tells Drake.
For the past five years or so, scientists working from Hubble Space Telescope images have suspected the moon sports a few plumes breaking out into space.
In other words, the spacecraft had flown through a localized plume maybe 620 miles wide somewhere near the moon's equator.
"When we first saw those images, I think a lot of us in the community were very excited", says planetary scientists Xianzhe Jia from the University of MI.
United States legislators this month TO approved a bill that would give $US545 million to the Europa Clipper mission.
Let's step back catch up on what scientists know about Europa and its newly confirmed gushers. And the density of charged particles surrounding the spacecraft would change as the spacecraft entered, flew through, and then exited the plume. McGrath is part of the Europa Clipper science team, too. The flybys will be less than 228 miles above the surface, which is in the observed range of the plumes, which can reach 124 to 228 miles above the surface.
"We know that Europa has a lot of the ingredients necessary for life, certainly for life as we know it". "That's what the mission is after". That's the big picture.