Long-term observations of Europe, a potentially inhabited satellite of Jupiter, made scientists doubt that giant geyser emissions are periodically born on its surface. This was told by planetary scientists who spoke at the annual meeting of the American Astronomical Society in Knoxville.
“We studied the data that the Galileo probe collected during its flights over the two points where Hubble and other telescopes recorded geyser emissions. We did not find anything special in these areas, no wormwood or other sources of heat. This was extremely surprising, since all geyser emissions on Enceladus are accompanied by similar traces,”said Julie Rathbun of the Planet Institute in Tucson (USA).
On Europa, one of the four largest moons of Jupiter, discovered by Galileo, there is an ocean of liquid water under a multi-kilometer layer of ice. Scientists consider Europa's ocean to be one of the likely refuge of extraterrestrial life. In recent years, astronomers have found that this ocean is exchanging gases and minerals with ice on the surface, and also confirmed the presence in it of substances necessary for the existence of microbes.
The first possible traces of the existence of geysers in Europe were found back in 2012, when the American astronomer Lorenz Roth discovered in the ultraviolet photographs of Europe, obtained with the help of the Hubble, traces of unusual "bright spots" in the region of the planet's south pole. Ros and his team counted these spots as eruptions of geysers rising 200 kilometers from the surface of Europa.
These observations attracted the attention of NASA scientists and they conducted several additional observing sessions of this moon in 2014, during which Hubble recorded three episodes of geyser eruptions. Two years ago, scientists found new hints of their existence by observing changes in Jupiter's ultraviolet glow caused by the ejection of water from Europa.
Later, planetary scientists found new traces of the existence of these emissions, analyzing data collected by the Galileo spacecraft in December 1997, when NASA's robotic station descended to the surface of Jupiter's moon at the point where geysers were found in the Hubble images.
Rathban and her colleague John Spencer of the Southwest Research Institute in Boulder, USA, studied the properties of these geysers by analyzing the data and comparing them with measurements from the Cassini probe, which studied Enceladus, a moon of Saturn. He repeatedly flew over the "tiger stripes", the valley of geysers at the south pole of this "lord of the rings" moon, and also studied their emissions.
Comparison of the data from Cassini and Galileo unexpectedly indicated that geysers on the surface of Europa could be fiction. Where they were supposed to be geysers, Europa's ice was as cold as in other regions of its surface.
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"All this suggests that either the geysers of Europe have some unique character that distinguishes them from both terrestrial hot springs and their 'cousins' on Enceladus, or it suggests that they do not exist or are extremely rare." Rathban concludes.
