Jupiter’s moon Europa has the solar system’s best chance to support life

New information came to light from the data collected during an old NASA mission. The Galileo unmanned spacecraft was launched in 1989 to study Jupiter and its moons. On December 16, 1997 it made its closest pass by the moon Europa at 124 miles above the surface and captured an anomaly in the data that seemed peculiar, but at the time did not lend scientists to believe an ocean made of liquid water could reside under its frozen surface. In 2012, however, evidence provided by the Hubble Space Telescope caused debate when it twice took ultraviolet pictures that appeared to be water plumes escaping from the moon’s icy shell.  

Galileo carried a powerful Plasma Wave Spectrometer which measured plasma waves caused by charged particles in gases around Europa’s atmosphere as well as a high-resolution magnetometer. Based on lessons learned from exploring plumes on Saturn’s moon Enceladus, scientists at the University of Michigan in Ann Arbor knew that material in plumes became ionized and left a characteristic blip in the magnetic field.  They ran the 21 year old data through their painstakingly created computer models to determine why, during the orbiter’s 1997 pass, there was that odd disruption in the magnetic field. They found the plasma and magnetic measurements were in line with what would happen if the spacecraft crossed a water plume. “These results provide strong independent evidence of the presence of plumes at Europa,” they reported in the scientific journal Nature Astronomy. That in turn was evidence of subsurface liquid water reservoirs.

Could Europa support life? The existence of liquid water makes it a better candidate than anywhere else in the solar system other than earth.

The findings are good news for NASA’s Europa Clipper mission, which could launch as early as 2022. From its orbit of Jupiter, Europa Clipper will make multiple fast, low-altitude flybys. If plumes are indeed forcing vapor from Europa’s ocean or subsurface lakes, it will sample the frozen liquid and dust particles.

“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,” says Europa Mission Project Scientist  Robert Pappalardo. “That’s what the mission is after.”