Jupiter’s ice-encrusted moon, Europe, increasingly looks like the best place in the solar system to search for alien life.
New modeling suggests the rock mantle, deep beneath the thick ice and salty ocean, may actually be hot enough for volcanic activity. Plus, it could have been this hot for most of its 4.5 billion year lifespan.
This finding has direct implications for the possibility that life is hiding on the seabed of Europe.
“Our results provide further evidence that the European underground ocean may be an environment conducive to the emergence of life”, said geophysicist Marie Běhounková from Charles University in the Czech Republic.
“Europe is one of the few planetary bodies that could have maintained volcanic activity for billions of years, and perhaps the only one beyond Earth that has large reservoirs of water and a source of water. ‘durable energy.”
You might think that a frozen world is a far cry from the Sun’s vital heat – where surface temperatures tend to peak at around -140 degrees Celsius (-225 degrees Fahrenheit) – would be an unlikely place to find living organisms, but there is actually a precedent here on Earth.
Granted, most of life here relies on a photosynthesis-based food web… but in some extreme environments, where the sun never shines, life has found another path.
In the dark depths of the ocean, too deep for sunlight to penetrate, volcanic vents ooze heat into the waters around them. There, life is built on chemosynthesis, bacteria that harness energy from geochemistry rather than solar energy to produce food.
Along with the bacteria come other organisms that can eat them, thus creating an entire ecosystem out there in the dark.
We know that Europa, beneath its thick sheet of ice, is home to a world ocean – we have seen liquid water spurting out of cracks in the ice in the form of geysers. We also detected what is most likely salt. This responds to some of the conditions of chemosynthetic hydrothermal life as we know it.
What we don’t know is if Europa has volcanic activity under its seabed, opening into vents like they do here on Earth.
It’s possible; Jupiter’s moon Io is the most volcanic world in the solar system, due to the constant stresses placed by Jupiter’s gravitational pull (and possibly the gravitational pull of other Jovian moons) that heat the interior.
Given that Europa is further from Jupiter than Io, however, there is still doubt – so Běhounková and his colleagues decided to try to figure it out.
They used detailed modeling to simulate the evolution and heating of the interior of Europe since its formation. They found several mechanisms in play that could work to keep the planet from freezing completely.
First, the heat given off by radioactive decay of mantle elements probably contributed to a significant fraction of the Mooninternal heat, especially at the beginning of European history.
Over time, however, the changing stresses generated by tidal forces exerted by the moonThe elliptical orbit around Jupiter should have produced continuous flexion inside Europa.
This bending, in turn, produces heat – and it should be enough to melt the rock into magma, resulting in volcanic activity that could continue today, especially in higher latitudes near the polar regions.
These simulations gave scientists signs of this activity to look for when probes such as NASA’s Europa Clipper and the JUpiter ICy Moons Explorer of the European Space Agency The (JUICE) mission (to be launched in 2024 and next year respectively) is getting closer to Europa.
Gravitational anomalies could suggest the presence of deep magmatic activity, and the abnormal presence of hydrogen and methane in Europe’s thin atmosphere could be the result of chemical reactions occurring at hydrothermal vents. Deposits of fresh oceanic material on the surface of Europe could also indicate underground activity.
“The prospect of a hot and rocky interior and volcanoes on the European seabed increases the chances that the European ocean will become a habitable environment”, said Robert Pappalardo, scientist of the Europa Clipper project from NASA’s Jet Propulsion Laboratory, which was not involved in the research.
“We may be able to test this with the gravity and composition measurements predicted by Europa Clipper, which is an exciting prospect.”
However, first we’ll have to wait a few more years for the spacecraft to get there. Curse the tyranny of distance!
The team’s research has been published in Geophysical research letters.