In an eagerly anticipated announcement, NASA just revealed new evidence that plumes of water are intermittently expelled from the surface of Europa, one of Jupiter’s moons.
It’s not quite as exciting as finding little green men skating across Europa’s ice-covered surface, but it could be a step in that direction. If alien life exists in our solar system, we’ll probably find it on Europa. Miles beneath its icy surface there is a liquid, saltwater ocean that could harbor life. If that’s the case, and if water sometimes spews out through the ice, that means we can study the water and look for signs of life without drilling through an unknown number of miles of ice to reach the ocean.
|The puzzling, fascinating surface of Jupiter's icy moon Europa, made |
from images taken by NASA's Galileo spacecraft in the late 1990s.
Image Credit: NASA/JPL-Caltech/SETI Institute.
The researchers say this work adds to the evidence in support of plumes, but caution that these ultraviolet images push the limits of what Hubble can do at that wavelength. They haven’t found anything else that could explain their results, but are eager for confirmation of their findings from more images or other techniques.
The first and, so far, only other evidence for water plumes also came from the Hubble. Spectroscopic data taken in 2012 indicated higher than expected amounts of hydrogen and oxygen above Europa’s surface, likely the result of water molecules from a plume and breaking up in the atmosphere. Both this and the new result suggest that the activity is primarily located around its south pole.
Europa’s surprisingly smooth surface was first revealed by NASA’s Voyager II space probe in 1978. The lack of craters and mountains suggested a deep ocean hidden beneath ice. If an object crashes into the Earth, we get a crater. If it crashes into Europa, it leaves behind a hole in the ice that refreezes. In addition, the pattern of cracks and streaks running across Europa’s surface is reminiscent of the icy surface of Antarctica where glaciers break apart, drift, and refreeze.
Scientists think that heat produced by tidal forces keeps the ocean from freezing solid. Volcanoes on the ocean floor could play a role as well. Although Europa has a thin atmosphere and Jupiter sends a lot of harmful radiation its way, life developing in the ocean would be protected by the icy cover.
A couple of years ago, scientists discovered what seems to be a huge saltwater lake just under Europa’s surface. This lake could act as a path along which energy and nutrients travel between the ice and the liquid ocean, creating an environment more conducive to life. Exactly how water might reach and break through the thick layer of ice covering the moon, even if it’s coming from the lake, is uncertain. Scientists have proposed models that show it is possible, but we really need more information to figure out what is happening.
|An artist's conception of one possible scenario for getting|
water to Europa's surface. Jupiter looms off to the right.
Image Credit: NASA/JPL-Caltech.
It’s tough to imagine life as we know it on an ice-covered planet, but where there is water on Earth, there is life. And if history is any indication, Europa likes making waves. Discovered in 1610 by Galileo Galilei, and independently by Simon Marius, Europa and the other three “Galilean moons” upset the accepted order of things at that time. Their trek through the sky clearly shows that not all celestial objects revolve around the Earth, an assertion that played a role in Galileo’s trial for heresy and house arrest. Of course, its ultimate acceptance was a huge leap forward for science and society. Will this new result bring us closer to another major turning point?