Scientists release new evidence of liquid water under Europa's icy crust

Yes, Europa really is sending plumes of water into space

Yes, Europa really is sending plumes of water into space

Europa has been a high priority for scientists because, as an ice-covered moon with a subsurface salty liquid ocean, it has been identified as one of the ideal spots for hosting life in our solar system. It appears that during some of those periodic observations, the telescope spotted evidence of water vapor emissions coming from Europa's surface. Now that we have this unearthed Galileo data, scientists can better plot the trajectory of the spacecraft to ensure we gather more data on these plumes, and Europa's subsurface ocean as a result.

According to Jai, data studied here showed "compelling independent evidence that there seems to be a plume on Europa". But that still means an orbiting spacecraft, like the Europa Clipper mission that's tentatively scheduled to launch in the early 2020s, could sample a plume and get a glimpse of what lies beneath the moon's ruddy, crisscrossed rind.

During one of the NASA Galileo probe's overflights, handled at a particularly low altitude of less than 150 km, scientists "saw signs that had never really understood", recalled Margaret Kivelson, one of the scientists on the Galileo mission, during a NASA broadcast of today.

At 1,900 miles (3,100 kilometers) wide, Europa is slightly smaller than Earth's moon.

Long considered to be one of the most promising places to search for alien life in the solar system, Europa is known to have a global ocean containing vastly more water than all of Earth's combined.

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.

"The. instruments are designed with Europa's plumes in mind, allowing us to infer the oceans composition and thus its suitability for life, and even to look for direct chemical signs of extant life", Vance said of the Europa Clipper mission.

When the three minutes of data associated with the plume were analyzed after the flyby in 1997, scientists thought it was a phenomenon of Jupiter's magnetic fields.

The 20-year-old data was captured on Galileo's closest encounter with the moon but scientists were unable to explain the unexpected signals at the time.

"The discovery is important because researchers will now try to program the next probe, Europa Clipper, to fly over the same area", said Elizabeth Turtle from the Johns Hopkins University.

The Galileo data were unique because the magnetometer was trying to detect changes in Europa's magnetic field as the probe approached the moon, like a boat going through water and creating waves. Both of these observations provide strong evidence of a plume, Jia said. For example, in the 2014 and 2016 candidate detections, the possible plumes blocked some ultraviolet light emitted by Jupiter. But the data also suggest the craft flew through a dense region of particles, something McGrath thought might come from Galileo flying through a watery plume. For starters, Jia said, the Galileo mission team wasn't specifically looking for plumes. "The data was already there, but we needed advanced technology to make sense of the observations", Jia said in a statement.

In a paper in the journal Nature Astronomy Jia describes how his team build custom 3D modelling code to work out a plume's density and properties, adding in the magnetic data from the Enceladus plume probe.

A mission called Europa Clipper was proposed several years ago. Jia layered the magnetometry and plasma wave signatures into new 3D modeling developed by his team at the University of MI, which simulated the interactions of plasma with solar system bodies. "To go from there to also there are geysers coming up from that ocean, we just weren't ready for that", Kivelson says.

While geysers spurting into space are cool on their own, it's an especially big deal if they exist on Europa.