|Above: A cutaway of th possible vents, warm ice blobs, and the internal ocean of Europa|
What's a surpthisrise is that this wasn't a discovery from a new Hubble image. This discovery was made by going over images of Europa from 2014, with two independent teams using new software and analytical techniques to tease the signature of the water plumes out of the data. Each used an different method, but both hit the same conclusion: The plumes are saline water. As Bill Sparks, from the the Space Telescope Science Institute in Baltimore puts it:
“When we calculate in a completely different way the amount of material that would be needed to create these … features... it’s pretty similar to what Roth and his team found. The estimates for the mass are similar, the estimates for the height of the plumes are similar. The latitude of two of the plume candidates we see corresponds to their earlier work,”Like any scientific discovery this one will need independent checking, and lots of arguing about on the internet*. We should all keep a pinch of doubt in mind about it until then. But it's a great boost for hopes of exploring Europa, and it's ocean: The case has never been more compelling. For a bit more detail I'll point you to the press relese here, the paper here, and pass you over to the NASA Goddard video:
*It's amazing how some people will happily believe aliens frequently come to Earth and steal our underwear while texting the Lizardmen and Illuminati, but will balk at the idea of a team of scientists teasing new information from old data with upgraded software.