In the early 1600’s Galileo Galilei made improvements to his telescope which then allowed him to discover four moons orbiting Jupiter.
In 1997, a NASA spacecraft named after him was sent to orbit Jupiter and its moons, and get a closer look at its atmosphere.
Scientists re-examining data collected by the Galileo spacecraft 21-years ago have been able to get new insights about the possibility of life on one of Jupiter’s moon, Europa. The data provides independent evidence that an ocean that lies below Europa’s icy surface may be venting plumes of water to the crust.
The decades-old data was put through new and advanced computer models to untangle a mystery — a brief, localized bend in the magnetic field — that scientists had been unable to explain until now.
Previous ultraviolet images from NASA’s Hubble Space Telescope in 2012 suggested the presence of plumes, but this new analysis used data collected much closer to the source and is considered strong evidence for the existence of these plumes.
The findings were recently published in the journal Nature Astronomy. Lead author Xianzhe Jia, a space physicist at the University of Michigan in Ann Arbor, said in a statement that the data were there but they needed sophisticated modeling to make sense of the observation. Jia is also co-investigator for two instruments that will travel aboard Europa Clipper, NASA’s upcoming mission to explore the moon’s potential habitability.
The decision to have another look at the old Galileo data was made after watching a presentation highlighting other Hubble observations of Europa by Melissa McGrath of the SETI Institute in Mountain View, California.
“One of the locations she mentioned rang a bell. Galileo actually did a flyby of that location, and it was the closest one we ever had. We realized we had to go back,” Jia is quoted as saying in the statement. “We needed to see whether there was anything in the data that could tell us whether or not there was a plume.”
The Galileo team didn’t suspect that in 1997 when the spacecraft was flying by roughly 200 kilometers above Europa’s surface, it might have been grazing a plume of water erupting from the moon. Now, Jia and his team believe, its path was fortuitous.
When they recently re-examined the information gathered during that flyby over two decades ago, the high-resolution magnetometer data showed them something strange. Drawing on what scientists learned from exploring plumes on Saturn’s moon Enceladus — that material in plumes becomes ionized and leaves a characteristic blip in the magnetic field — they knew what to look for. And there it was on Europa –- a brief, localized bend in the magnetic field that had never been explained.
The Galileo spacecraft carried a powerful Plasma Wave Spectrometer (PWS) to measure plasma waves caused by charged particles in gases around Europa’s atmosphere. This data also appeared to back the theory of a plume.
However, numbers alone could not paint the whole picture. Jia layered the magnetometry and plasma wave signatures into new 3D modeling developed by his team at the University of Michigan, which simulated the interactions of plasma with solar system bodies. The final ingredient was the data from Hubble that suggested dimensions of potential plumes. The result that emerged, with a simulated plume, was a match to the magnetic field and plasma signatures the team pulled from the Galileo data.
“There now seem to be too many lines of evidence to dismiss plumes at Europa,” said Robert Pappalardo, Europa Clipper project scientist at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California. “This result makes the plumes seem to be much more real and, for me, is a tipping point. These are no longer uncertain blips on a faraway image”
The findings are good news for the Europa Clipper mission, which according to NASA may launch as early as June 2022. From its orbit of Jupiter, Europa Clipper will sail close by the moon in rapid, low-altitude flybys. If plumes are being spewed from Europa’s ocean or sub-surface lakes, Europa Clipper’s instruments could collect samples of the frozen liquid and dust particles.
According to the statement, the mission is looking at potential orbital paths, and the new research will play into those discussions.
“If plumes exist, and we can directly sample what’s coming from the interior of Europa, then we can more easily get at whether Europa has the ingredients for life,” Pappalardo said. “That’s what the mission is after. That’s the big picture.”