Observations have already confirmed the existence of a sub-surface ocean on Europa, and there has been rampant speculation about whether they could contain life. While there have been tentative plans to send a submersible spacecraft to this ocean, we are still a long way from uncovering what lies in those depths.
Which is one big reason why the geysers that occasionally shoot out of Europa’s ice sheet have garnered such interest. Scientists hoped that some of the ejected water could come from that ocean. It could then be sampled with a simple fly-by mission, such as Europa Clipper, rather than a submersible craft. However, a new paper published in Geophysical Research Letters suggests a much more mundane source of the geysers – local liquid water buried in the moon’s thick ice shelf.
The paper, written by an interdisciplinary team from Stanford, the University of Arizona, the University of Texas, and NASA’s JPL, used data from the Galileo spacecraft, which made multiple flybys of the moon. The data they focused on Manannán, a crater that was created millions of years ago when the moon collided with a comet or asteroid sized object.
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The team modeled how the extreme heat released by the impact could have affected the local ice shelf. In particular what they found is that some of the local ice would have melted, though most refroze in the later stages of the impact, some could have potentially absorbed enough salt to remain liquid even after the impact itself is over.
Not only could some of the water have potentially stayed liquid after the impact, it could also have started moving around in the ice sheet itself. Part of the team’s model demonstrates these isolated pocket’s ability to melt adjacent ice patches due to their increased salinity. These liquid patches can then travel around inside the ice sheet, and when they meet a particularly loose piece of the ice sheet covering Europa’s surface, could explode into the geysers the moon is so famous for. Unfortunately, that means it is less likely that these geysers come from the sub-surface ocean, and therefore we are less likely to find biological signatures in them.
Admittedly the work so far is modeling based on preliminary data from Galileo. As with almost all things science, further data is needed, and the team hopes to receive some from the Radar for Europa Assessment and Sounding: Ocean to Near-surface (REASON) instrument on the Europa Clipper mission. One of the co-authors of this new paper, Dr. Don Blankenship at the University of Texas Institute for Geophysics, is also the principal investigator for REASON, and is focused on ensuring that his instrument is capable of collecting data that can test the hypothesis developed in this paper.
They will have to wait a while to collect any of that data, as the Europa Clipper mission is scheduled to arrive at the moon in approximately 2030. Until then, there are plenty of other data sets from Galileo that could use a second glance, as this team has already proven.
Stanford: Stanford researchers model source of eurption on Jupiter’s moon Europa
Geophysical Research Letters: Brine Migration and Impact-Induced Cryovolcanism on Europa
UT: Even More Evidence that Europa has Geysers
Lead Image Credit: Justice Blaine Wainwright