The mysterious and incomprehensible mysterious vapor of Europa's water vapor on Europa is indeed real.
NASA's Hubble Space Telescope has found indirect evidence like that feathers that come from Europa, which is thought to store large, salty oceans beneath the ice sheet. And researchers have now detected vapor like plume directly for the first time, a new study reports.
"Important chemical elements (carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur) and energy sources, two of the three requirements for life, are found throughout solar system. But the third – liquid water – is rather difficult to find outside of Earth, "said study leader Lucas Paganini, a planetary scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, and the American University in Washington, D.C., in a statement.
"While scientists have not detected liquid water directly, we have found the next best thing: water in the form of steam," added Paganini.
Related: Possible Clumps of Water on Europa: Discoveries in Figs
Paganini and his colleagues used W.M. Keck Observatory in Hawaii to study Europa 1,900 miles (3,100 kilometers) wide, which astrobiologists consider to be one of the solar systems. the best bet to host a foreign life.
The researchers observed Europa for 17 nights, from February 2016 to May 2017. On one of those nights – 26 April 2016 – they got a strong signal of water vapor, in the form of the characteristic wavelength of infrared light emitted.
And there are enough goods – around 2,300 tons (2,095 metric tons), according to the researchers' calculations. That is almost enough to fill an Olympic size swimming pool (which contains about 2,750 tons, or 2,500 metric tons, of water).
The researchers think this water source is feathers, which can come from buried seas or from melted ice reservoirs in Europa's skin. For starters, the observed volume is much higher than thought to be produced from "exogenic" processes, such as stripping water molecules from the surface of Europa by Jupiter's strong radiation belt. And such stripping is likely to occur regularly, or at least often enough to be recorded more than one night out of 17, Paganini and his team write in new paper, which is published online today (November 18) in the journal Nature Astronomy.
Much evidence now points to the existence of feathers on Europa. For example, in addition to new results and Hubble's detection of hydrogen and oxygen atoms (which may come from water molecules split by radiation), NASA's Galileo Jupiter investigation measured a large increase in plasma density, or ionized gas, during the Europa flight in 1997.
And it is increasingly clear that Europa feathers are sporadic. In that respect, they are very different from the constant feathers that hover from the cold south pole of Saturn's moon, harboring the ocean Enceladus, which is produced by more than 100 powerful geysers that are always active.
"For me, the interesting thing about this work is not only the first direct detection of water above Europa, but also its shortcomings within the limits of our detection method," Paganini said.
Feathers such as those from Enceladus and Europa are of great interest to astrobiologists, because they send "free samples" from potentially habitable environments to space for possible snagging by robotic probes. And there is a possibility that NASA spacecraft could immediately do that, if all went well.
NASA is developing a mission called Europa Clipper, which is scheduled to launch in the mid-2020s. The Clipper will orbit Jupiter but study Europa closely with dozens of flybys, characterize the moon and ocean and hunt for points where potential life hunters can land in the future. Clippers can zoom in feathers on one or more of these flybys, if the members of the mission team learn enough about these features in the coming years – or if they are really lucky.
Mike Wall's book about the search for alien life, "Out there"(Grand Central Publishing, 2018; illustrated by Karl Tate), is out now. Follow him on Twitter @michaeldwall. Follow us on Twitter @Spacedotcom or Facebook.