The Hubble Orbital Observatory has received new photographs of 100-kilometer geysers on the surface of Europa, originating in the same point on the planet where they were found three years ago, according to an article published in the Astrophysical Journal Letters.
“Not all of us think so, but in my opinion, this discovery makes us look optimistic about the signs of the existence of geysers in Europe. The repeated surge in the same place tells us, in terms of statistics, that this cannot happen by chance. We tried to find other explanations for this, including the existence of problems with the tools. Nothing like that was found, and most of us think that the geysers are real,”said William Sparks of the Space Telescope Institute in Baltimore (USA).
Secrets of water worlds
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 using the Hubble, traces of unusual light spots in the region of the planet's south pole. Ros and his team counted these spots as eruptions of geysers, rising to a gigantic height tens of kilometers from the surface of Europa.
These observations attracted the attention of NASA scientists and they conducted several additional observing sessions of Europe in 2014, during which Hubble recorded three episodes of geyser eruptions. Not all scientists, as noted by Sparks, believed this and considered the images of the Hubble, obtained at the limit of its resolution, the fruit of artifacts and failures in instruments.
This led Sparks and the Hubble research team to conduct a series of additional observations of Europe in an attempt to prove that they were right and the skeptics were wrong. To do this, they needed not only the power of a veteran telescope, but also help from the past.
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Help from the past
NASA scientists were observing the geysers using a well-established technique - they followed the planet at the moment when it passed along the bright disk of Jupiter, and tried to find dark spots on the surface of Europa, which appeared at the moment when geysers threw water into space and covered with themselves ultraviolet glow of the giant planet.
A place on the surface of Europe, where the geysers of 2013 and 2016 are believed to have originated. NASA / ESA / W. Sparks (STScI) / USGS Astrogeology Science Center NASA / ESA / W. Sparks (STScI) / USGS Astrogeology Science Center
They managed to do this at the end of February last year, when traces of geyser activity appeared in the same region at the south pole of Europe, where they were found in March 2014. This time, the geysers were even more active than three years ago, and the height of their emissions, according to estimates by Sparks and his colleagues, reached about 100 kilometers.
Infrared images from the Galileo probe taken in the late 1990s provide additional confirmation that geysers may form in this part of Europe. On them, according to scientists, you can see that the part of Europe where the geysers they found appear is about 2-3 degrees warmer than other regions of the planet. This suggests that the ice beneath it is noticeably thinner and that a warm ocean is hidden under it, periodically breaking out.
It remains unclear how geysers are born - the power of Jupiter's tidal forces, as scientists admit, is not enough to break the thick enough ice sheet of Europa and help water penetrate through it. Scientists hope that the flights of the Europa-Clipper probe through the geyser emissions will help reveal this mystery, as well as find out whether life exists in the waters of Europe or not.