Scientists have always theorized that liquid water exists under Europa’s icy crust, and with that theory the possibility that life exists. Now there is apparently proof of water – in the form of geysers shooting it 200 km above the surface of the Jovian moon.
Artist’s depiction of Europa’s subsurface ocean, crust and geysers. (Credit: NASA/JPL)
In 2012, the Hubble Space Telescope detected signs of oxygen and hydrogen above Europa’s southern pole. This led to speculation that that water was getting shot out from under the surface and making it well above the surface where radiation from Jupiter split it into its two elements. In 2014, Hubble gathered more evidence of the plumes, but still no proof. Recently, Hubble yet again detected plumes of water from near Europa’s southern pole. Rather than looking directly for the plumes, the space telescope looked at the moon when it crossed in front of Jupiter and on three occasions saw what appeared to be materials from the plumes back lit against the massive planet. While still not concrete proof, it is yet more evidence pointing to water.
Geysers on Enceladus photographed by the Cassini spacecraft. (Credit: NASA)
Additionally, there is evidence of salt deposits on Europa’s surface, which leads researchers to believe water is interacting with the moon’s rocky core. Geysers much like those presumed to be on Europa exist on Enceladus, and deposit a sort of salty water in many places on the surface, but unlike on the diminutive moon of Saturn, those on Europa don’t seem to continuously erupt. They blow their tops only when Europa is farthest from Jupiter in its orbit. It’s estimated that Europa’s geysers spew forth more than 350 times the material of those on Enceladus.
Image of Europa showing surface cracks. (Credit: NASA)
Across Europa’s icy surface runs its most striking feature: a series of dark brown lines that seem to be etched into the crust—the largest measuring more than 20 km wide. The prevailing theory is that extreme tidal forces from Jupiter and other moons split the thick ice-sheet crust, then liquid water from underneath fills the crack and freezes to form Europa’s signature dark lines. Researchers have simulated this process on Earth by taking sea water and bombarding it with radiation. The results show a nearly identical color change of the salt from white to the rust-brown we see on Europa’s thick ice surface.[i]
How Thick is Thick?
Some researchers believe Europa’s ice sheets to be as thick as 10 to 30 km (6 to 10 miles). It takes a tremendous amount of force to crack ice that thick, and Jupiter supplies it. Tidal forces are estimated to be 1,000 times those we experience on Earth from our Moon. Under the ice sheet, the water part of the ocean is potentially as deep at 100 km (60 miles). That’s as much as two to three times all the water on Earth.
Why is These Geysers Important?
The search for life in our solar system has been picking up steam as spacecraft capable of detecting it are brought online and launched. Europa is widely regarded as one of the most likely places that life could exist, and if microbes are present in the moon’s liquid ocean, then it is likely that either the organisms themselves or evidence of their presence would be blasted into space from the geysers along with the water. Instead of having to land a rover on the surface of Europa to detect life, a spacecraft could simply fly through a plume and capture samples.
Missions to Europa
In January of 2016, NASA announced plans for a yet-to-be-named mission to Europa. It would launch in the 2020s, arriving late in the decade, and make 45 flybys close to Jupiter and Europa, completing one every two weeks. They would range in altitude from 25 km to 2,700 km (16 to 1,700 miles). The mission will include magnetic sensors to determine the thickness of the ice sheet and depth of the ocean and imaging equipment to map the surface and help determine its exact composition. It would also use a thermal imaging system to help detect geysers and radar to map details of the ice sheet.
Finally, a mass spectrometer and dust analyzer would determine the exact composition of the atmosphere and geyser material, and an ultraviolet spectrograph would also gather data about the geysers and atmosphere.
More About Life in Our Solar System
In October, Darren Beyer will publish one of his two non-fiction ebooks: Out There – The Ten Most Likely Places to Discover Life in Our Solar System. Sign up for Darren’s mailing list to get a free pre-release copy.
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