May 15, 2018
A NASA probe that explored Jupiter’s moon Europa flew through a giant plume of water vapor that had erupted from the icy surface and reached a hundred miles high, according to a recent analysis of the spacecraft’s data. The revelation of water vapor on an alien moon brings credence to the theory that Europa could host life.
The Galileo spacecraft spent eight years in orbit around Jupiter and made its closest pass over Europa, a moon about the size of our own, on December 16, 1997. As the probe dropped beneath an altitude of 250 miles, its sensors twitched with unexpected signals that scientists were unable to explain at the time.
In a new study, the researchers decided to go all the way back to the Galileo data after grainy images beamed home from the Hubble space telescope in 2016 showed what appeared to be plumes of water blasting from Europa’s surface. They found that a sudden blast of water from the moon explained the Galileo probe’s strange measurements.
Galileo swept over Europa at more than 2,230 mph during it’s closest flyby. As it hurtled past, instruments onboard the probe detected a brief but dramatic twist in the magnetic field and a sudden, rapid increase in the density of the plasma, or ionized gas, the spacecraft was flying through. Computer simulations created by Xianzhe Jia, a space scientist at the University of Michigan, showed that a 120-mile-high geyser erupting from a relatively warm patch on Europa would create precisely the same readings.
When plumes of water spray out of Europa, the molecules are immediately battered by highly energetic particles, a process that smashes them into charged ions. It is these ions that produce rapid swings in the magnetic field direction and ramp up the density of plasma above the geyser.
Details of the work appear in the journal Nature Astronomy.
According to The Guardian, the discovery has cemented the view among some scientists that the Jovian moon, one of four first spotted by the Italian astronomer Galileo Galilei in 1610, is the most promising place in the solar system to hunt for alien life.
If such geysers are common on Europa, NASA and the European Space Agency (ESA) missions that are already in the pipeline could fly through and look for signs of life in the brine, which comes from a vast subsurface ocean containing twice as much water as all the oceans on Earth.
“There were some anomalous features in that close pass in December 1997 that we never fully understood,” said Margaret Kivelson, a senior scientist on the Galileo mission and emeritus professor of space physics at the University of California in Los Angeles. “We went back and looked at them more carefully and found that they were just what you’d expect if we’d flown through a [water vapor] plume.”
“Our detection of a plume based on the Galileo data certainly strengthens the case for future exploration of Europa,” Jia said. A NASA mission, Europa Clipper, is scheduled to launch in the 2020s with the express aim of finding out whether the moon could possibly harbor life. Another mission, the ESA’s Jupiter Icy Moons Explorer, or “Juice,” is expected to launch around the same time and perform flybys of Europa and two of Jupiter’s other moons, Ganymede and Callisto.
“Given the evidence of plumes available so far, there is a good chance that those spacecraft may obtain direct measurements of plumes ejecting material from the subsurface ocean into space,” said Jia. “Those observations will provide crucial information for us to assess Europa’s potential for life.”
This article was posted: Tuesday, May 15, 2018 at 5:46 am