Artist’s illustration of Jupiter and Europa (in the foreground) with the Galileo spacecraft after its pass through a plume erupting from Europa’s surface. A new computer simulation gives us an idea of how the magnetic field interacted with a plume. The magnetic field lines (depicted in blue) show how the plume interacts with the ambient flow of Jovian plasma. The red colors on the lines show more dense areas of plasma. (Credits: NASA/JPL-Caltech/Univ. of Michigan)*
What NASA’s Galileo mission in 1997 did on the fly over Europa, literally and otherwise, has now yielded some extraordinary insights about one of Jupiter’s 53 moons.
It is a tribute to how persistent scientists can be that an unexplained bend in the magnetic field from 21 years ago was revisited to discover that it was caused by plumes of water vapor bursting out from Europa’s subsurface liquid water.
“Data collected by NASA’s Galileo spacecraft in 1997 were put through new and advanced computer models to untangle a mystery -- a brief, localized bend in the magnetic field -- that had gone unexplained 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, corroborating support for plumes,” NASA says.
This is a remarkable finding that makes Europa one of the most likely places for potential life in our solar system other than on Earth. It is already known that Europa, which is slightly smaller than our Moon, has more water under its frozen upper crust than the whole of Earth. It has been long speculated that given so much liquid water it may not be altogether inconceivable that there may be some form of life on Europa.
This particular research was led by Xianzhe Jia, a space physicist at the University of Michigan in Ann Arbor. What I find fascinating is how scientists connect dots over long periods of time and how fortuitously.
As NASA explains:
“Jia’s team was inspired to dive back into the Galileo data by Melissa McGrath of the SETI Institute in Mountain View, California. A member of the Europa Clipper science team, McGrath delivered a presentation to fellow team scientists, highlighting other Hubble observations of Europa.
“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 said. “We needed to see whether there was anything in the data that could tell us whether or not there was a plume.”
At the time of the 1997 flyby, about 124 miles (200 kilometers) above Europa’s surface, the Galileo team didn't suspect the spacecraft might be grazing a plume erupting from the icy moon. Now, Jia and his team believe, its path was fortuitous.”
It is because McGrath was paying attention to some old data that prompted Jia to employ the now more sophisticated data analysis techniques compared to over two decades ago. So we now know that quite like Saturn’s moon Enceladus, Europa too vents water vapor. Enceladus’ plumes were discovered and photographed spectacularly by NASA’s Cassini mission in 2009.
To illustrate how scientists connect dots that might seem unconnected to an untrained mind, here is what NASA says about the Europa findings: “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.”
This also shows how scientific phenomena such as a bend in a magnetic field can be universal. Science works because it has a certain logical predictability and verity built into it.
The Europa discovery could not have come at a more opportune time considering NASA is preparing for the Clipper mission to Jupiter scheduled for launch in June 2022.
* I have used the NASA caption verbatim.