Scientists find evidence of water plumes erupting on Europa
Sen—Astronomers have found evidence that water plumes may be erupting from one of Jupiter's largest moons, Europa.
The new study is based on data from the Hubble Space Telescope which detected water vapor up to 201 km (125 miles) above Europa's south polar region in December 2012. Europa is thought to have an underground ocean, and scientists believe the most likely explanation of the water vapor to be the eruption of water plumes from the moon's surface.
“By far the simplest explanation for this water vapor is that it erupted from plumes on the surface of Europa,” explained Lorenz Roth of Southwest Research Institute in San Antonio and lead author of the research paper.
"If those plumes are connected with the subsurface water ocean we are confident exists under Europa's crust, then this means that future investigations can directly investigate the chemical makeup of Europa's potentially habitable environment without drilling through layers of ice. And that is tremendously exciting."
Graphic showing the location of water vapor detected over Europa's south pole in observations taken by the Hubble Space Telescope in December 2012. Credit: NASA/ESA/L. Roth/SWRI/University of Cologne
If water jets are spurting out of Europa it will be the second moon in the Solar System to possess such a characteristic -- jets of water ice and organic compounds have been found bursting from Saturn's tiny moon Enceladus. The Cassini spacecraft orbiting Saturn has flown through and 'tasted' Enceladus' spray on several occasions, detecting salt in the icy particles similar to that found in Earth's oceans.
Whilst Enceladus' jets erupt from the surface through its "tiger stripes" -- four parallel claw marks about 120 km in length scratched into the icy surface -- the water vapor over the south polar region of Europa could be escaping from long cracks on its surface known as lineae.
The researchers also found another common theme with Enceladus - the intensity of the plumes varies with the moon's orbital position, with the vapor trail only apparent when the moon is farthest from Jupiter. This could be explained by the effect of stronger gravitational tidal forces on the lineae which are stretched more at larger distances from the planet, opening the 'vents' for the jets to escape. The vents are narrowed or closed when Europa is closest to Jupiter.
"The apparent plume variability supports a key prediction that Europa should tidally flex by a significant amount if it has a subsurface ocean," said Kurt Retherford, also of Southwest Research Institute.
NASA's John Grunsfeld commented: “If confirmed, this new observation once again shows the power of the Hubble Space Telescope to explore and opens a new chapter in our search for potentially habitable environments in our solar system.”
Europa is one of the four Galilean moons discovered by Galileo Galilei in 1610. The moon is thought to have a salty ocean beneath its icy crust which could be 100 km deep and a potential place to look for alien life. Europe is building a probe to study Europa, as well as two of the other Galilean moons, Callisto and Ganymede. The Juicy Icy Moons Explorer -- known as JUICE -- is due to launch in 2022 and arrive in orbit around Jupiter in 2030.
Europa is 3,140 km in diameter and lies 671,000 km from Jupiter, orbiting once every 3.55 days.
The new research is published in Science Express and was reported at a meeting of the American Geophysical Union in San Francisco.