Scientists compared images of Europa, a moon of Jupiter, and Greenland to estimate the water was a few meters below the surface. And with water life?
Europa, a moon of the planet Jupiter, may be holding back pockets of water just below its icy surface, according to scientists who based their hypothesis on observation of Greenland’s surface.
The star is one of the prime candidates for searching for extraterrestrial life in the solar system due to the alleged existence of an ocean of liquid water. However, the latter would be under a thick layer of ice, up to 20 to 30 kilometers below the surface, according to data collected by spacecraft.
However, some of that water may be much closer to the surface than previously thought, according to the study published in Nature Communications on Tuesday, which underscores that Europa is “young and geologically active”. The most common structure there consists of double ridges, a type of ridges that extend for hundreds of kilometers and whose edges can rise to several hundred meters.
Climate change as an indicator?
Scientists have advanced several hypotheses to explain their formation, most notably an interaction between the inner ocean and the sheet of ice that covers it. But the difficulty for water to penetrate such a thick surface has led to speculation that the formation of the ridges occurs with pockets of water located just below the surface. That’s exactly what a team of geophysicists from the American University of Stanford observed… in Greenland, a mostly ice-covered island.
There they discovered “a double ice ridge similar in shape to the double ridges found on Europa,” said Riley Culberg, an electrical engineering graduate student at Stanford and lead author of the study. It is about 800 meters long with an average height of 2.1 meters and is located about 60 km from the coast in north-west Greenland.
Colleague Dustin Schroeder, a professor of geophysics at Stanford, explains that when we saw these little double ridges, they were “working on something very different in terms of climate change and its impact on Greenland’s surface.”
Two space missions from 2030
Satellite imagery and data collected by aircraft radar made it possible “to see something similar (Europa) on Earth for the first time and to observe the subsurface processes that led to the formation of the ridges,” said Riley Culberg. The team modeled a process involving the freezing, pressurization and rupture of a shallow pocket of water, leading to the formation of the double ridge.
“The water that we observed in Greenland is in the first 30 meters of the ice sheet,” explains Dustin Culberg. On Europa, whose ridges are much higher and longer, he estimates that “pockets of water could form between one and five kilometers deep.”
If their mechanism of formation is indeed the proposed one, these pockets could be very widespread. And if the water they’re made of comes from the inner ocean, they could contain traces of extraterrestrial life.
Two future space missions will provide more information from 2030 onwards. Europa Clipper for NASA will be equipped with a radar similar to that used to survey Greenland. JUICE for the European Space Agency (ESA) will also look at Europa, as well as Jupiter’s other two icy moons, Io and Ganymede.