Scientists using the Hubble telescope have discovered what appear to be 125-mile high geysers of water spouting from the surface of EuropaIf the geysers are coming from oceans underneath the moon's outer layer, rather than shallow pools, they could be an indicator of life on the planet.

Researchers learned decades ago that Europa, a moon of Jupiter, is covered by a thick layer of ice. Detailed images revealed liquid water on the planet, and geysers were suspected but not seen when astronomers looked at Europa through the Hubble telescope in 1999. Last year, however, Lorenz Roth, lead author of the report outlining the discovery, "Transient Water Vapor at Europa's South Pole," looked again and saw a UV glow above Europa's southern hemisphere, indicating what they believe to be spouts of water. 

According to Slate, the fact that the geysers weren't seen in 1999 actually lends credence to Roth's discovery. Europa follows an elliptical path around Jupiter, and its gravitational pull is weakened when it is more distant from the planet. Slate's Phil Plait explains

Those older observations were taken when Europa was close to Jupiter, but the new observations were taken when Europa was farther away.... This means that any deep cracks in the surface are squeezed closed when Europa is near Jupiter and relaxed, opened up, when it’s farther away. If water from the subsurface ocean were to escape through cracks, it would be when they’re open. So these observations precisely fit the idea that this is what we’re seeing.

Researchers will look through Hubble again in an effort to confirm that what Roth and his colleagues saw were, indeed, H2O geysers. If they are, NASA might push forward with plans to launch a probe to explore Europa. As one of the few bodies in all of the solar system to contain liquid water, human should be very interested in what we might find there.