Fifteen years after the NASA probe burned up in Jupiter's atmosphere, newly analyzed magnetic and plasma data from the mission have bolstered evidence that Europa, the planet's ice-bound moon, is likely venting water into space.
"A signature located in the MAG data acquired at Galileo's closest encounter with Europe is totally consistent with the expected disturbances if the spacecraft were to pass through a plume that rises above the nearby surface", states the science team's members in the study's report.
The tallest of the plumes was so powerful that it extended 193km above the moon's surface; Old Faithful, the famous geyser at Yellowstone, reaches 56 metres.
One ardent supporter of a mission to Europa, Texas Congressman John Culberson, broke the embargo on this news last week during a Congressional hearing on NASA's budget.
At 1,900 miles (3,100 kilometers) wide, Europa is slightly smaller than Earth's moon. This mission would launch in the 2020s and would pass by Europa enough times to (hopefully) detect water plumes with more confidence than ever found before.
It is thought to have an iron core, a rocky mantle and a surface ocean of salty water, like Earth. The solar system's ocean worlds might be the most promising place to look.
"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", he said in a statement. The experiments showed Europa possesses an atmosphere. In late 2012, Hubble spotted signs of such a feature near the moon's south pole. If researchers want to know if some form of life has indeed taken root inside the planet, studying those plumes may be the easiest way to prove it.
According to Jai, data studied here showed "compelling independent evidence that there seems to be a plume on Europa". They also examined data from Galileo's spectrometer, which measured the presence and behavior of charged particles. Galileo flew by Europa a total of 11 times. 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.
In addition, "to make sense of the observations, we had to really go for sophisticated numerical modeling" techniques, he told Space.com. So Jia, Kivelson and their colleagues ran the data through a sophisticated modelling program that compared the observations with what scientists might expect to see from a plume of the dimensions reported by Hubble.
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.
To find out more the Europa Clipper mission will make over 40 close flybys of the moon's surface, some only tens of kilometers up. Philips noted that collected plume material might not even be a direct sample of ocean water, but it would still "yield important insights into the composition of materials within Europa, and the potential for habitability-could there be environments on Europa where life could survive?" The mission will also carry a magnetometer to measure the strength and direction of the moon's magnetic field, which will allow scientists to determine the depth and salinity of its ocean.