Photo: This photograph of the Jovian moon Europa was taken in June 1997 at a range of 776,700 miles by NASA's Galileo spacecraft. Slightly smaller than Earth's moon, Europa has a very smooth surface and the solid ice crust has the appearance of a cracked eggshell. The interior has a global ocean with more water than found on Earth. It could possibly harbor life as we know it. Hubble Space Telescope observations of Europa have revealed the presence of persistent water vapor in its very tenuous atmosphere. Hubble observations, spanning 1999 to 2015, find that water vapor is constantly being replenished throughout one hemisphere of the moon. This is a different finding from Hubble's 2013 observations that found localized water vapor from geysers venting from its subsurface ocean. This water vapor comes from a different process entirely. Sunlight causes the surface ice to sublimate, transitioning directly into gas. This color composite Galileo view combines violet, green, and infrared images. The view of the moon is shown in natural color (left) and in enhanced color designed to bring out subtle color differences in the surface (right). The bright white and bluish part of Europa's surface is composed mostly of water ice, with very few non-ice materials. Long, dark lines are fractures in the crust, some of which are more than 1,850 miles long. Credit: NASA, NASA-JPL, University of Arizona
NASA scientists operating the Hubble Space telescope have discovered a persistent water presence on Europa, a moon of the planet Jupiter.
Curiously the water only exists in one hemisphere.
The scientists now believe that Europa has vast oceans underneath its icy surface, which they speculate could harbour lifeforms.
Scientists and astronomers had long believed that Europa held water, even if it was not proven until now. They were first made aware of the possibility of water from what they believed were water vapours observed in the moon's atmosphere and by what they thought were plumes erupting like volcanoes from the surface of the satellite. Thanks to the new investigation by Hubble, it is now known that these plumes do in-fact exist and that they are geysers shooting liquid 60 miles into Europa's atmosphere. Europa's surface itself sits at minus 260 degrees Fahrenheit, meaning any potential life will have had to have adapted to such extreme temperatures.
The recent conclusions about Europa come after almost two decades of work by NASA and Hubble. The Hubble telescope utilised Space Telescope Imaging Spectrograph (STIS) when evaluating Europa. This technique uses ultraviolet beams which change as they return to the telescope depending on whether or not they have bounced off liquid.
Perhaps most striking is that the liquid is only known to exist in the advancing portion of Europa, the hemisphere that is moving first through orbit, while the trailing hemisphere of Europa shows no current signs of liquid at all. Scientists have no current explanation as to why this is.
Europa is not the first moon of Jupiter to be found to have liquid upon it. Ganymede, another moon, has also been verified as containing liquid, and many of the same techniques used to determine the composition of Ganymede were used when researching Europa.
Lorenz Roth of the KTH Royal Institute of Technology, Space and Plasma Physics, who explored and collated much of the NASA data on Europa, said of the findings:
"The observation of water vapor on Ganymede, and on the trailing side of Europa, advances our understanding of the atmospheres of icy moons. However, the detection of a stable water abundance on Europa is a bit more surprising than on Ganymede because Europa's surface temperatures are lower than Ganymede's."
[h/t: Phys.org]
COMMENTS