A new analysis suggests the spacecraft saw water vapor jetting from Jupiter’s icy moon
JPL-Caltech/NASA, SETI Institute
Jupiter’s icy moon Europa may have been spitting into space for at least 20 years. Analyzing old Galileo mission data suggests that the NASA spacecraft flew through a plume of water vapor from the moon during a 1997 flyby, researchers report May 14 in Nature Astronomy.
“We now have very compelling support for the idea that Europa does possess plumes,” says study coauthor Xianzhe Jia, a planetary scientist at the University of Michigan in Ann Arbor.
Whether the moon, Jupiter’s fourth largest, has such geysers has been a lingering mystery. One of the most tantalizing results from Galileo, which orbited Jupiter from 1995 to 2003, was evidence that Europa harbors a deep ocean of liquid water beneath an icy shell. Then in 2012, data from the Hubble Space Telescope revealed high concentrations of charged hydrogen and oxygen atoms, or ions, over Europa’s southern hemisphere, a potential sign of water vapor escaping into space (SN: 1/25/14, p. 6).
The putative plumes have played peekaboo ever since (SN Online: 1/11/18), continuing to intrigue astronomers hoping to search the moon's water for signs of life.
Galileo found no other signs of plumes during its 10 other Europa flybys, which were farther away from the moon. That suggests that any plumes are relatively small, extending not much higher than 200 kilometers above the surface. It’s also unclear if Europa plumes would be spewing constantly or be turning on and off.
Jia is working on magnetic field and plasma instruments for two future missions to Jupiter and its moons: the 2022 European JUICE mission and NASA’s Europa Clipper spacecraft, also planned for the early 2020s. The Clipper spacecraft will make much lower flybys over Europa, skimming as low as 25 kilometers above the surface. The new Galileo results should help in planning those flight paths, he says.
Planetary scientist Cynthia Phillips of NASA’s Jet Propulsion Laboratory in Pasadena, Calif., who worked on Galileo as a graduate student but was not involved in the new analysis, says it’s exciting that scientists are using new tools on the old mission data.
“During Galileo, we’d always known there was something weird during this flyby,” she says. But she is still holding out for visual confirmation of the plumes. “Pictures, or it didn’t happen.”
X. Jia et al. Evidence of a plume on Europa from Galileo magnetic and plasma wave signatures. Nature Astronomy. Published online May 14, 2018. doi:10.1038/s41550-018-0450-z.
L. Grossman. Hubble telescope ramps up search for Europa’s watery plumes. Science News Online, January 11, 2018.
C. Crockett. Europa spouting off again. Science News Online, September 26, 2016.
A. Grant. Europa vents water, Hubble data suggest. Science News. Vol. 185, January 25, 2014, p. 6.