In a new paper published in Nature Astronomy, Tom Nordheim from the Jet Propulsion Laboratory in Pasadena and his colleagues put Jupiter’s moon Europa back on the front burner in the search for life beyond Earth.
They found that potential biosignatures such as amino acids might be preserved at high to mid-latitudes of Europa only a few centimeters below the moon’s icy surface. Even in the equatorial regions, where the radiation hazard is much more brutal, detectable levels of amino acids may still be recoverable at depths of only 10 centimeters—assuming the ice crust is not older than 10 million years.
On our own planet, of course, water ice is great for preserving biological molecules. The problem on Europa is the huge amount of radiation that this moon receives from Jupiter. A lander mission would be challenging, as the spacecraft would have to be radiation-hardened. A human mission is completely out of the question.
But the astonishing results by Nordheim and colleagues, if validated by other research groups, open up new possibilities for exploration. If a spacecraft were to land in the right location on Europa, it would need only a heat source to melt the ice and a scooper to collect biologically interesting samples. No deep drilling would be necessary, which saves a lot of technology development and expense.
Ideally, a Europa lander would search for biomolecules in regions on the moon’s surface younger than the average age of 30 to 90 million years old (which is still comparatively young compared to other icy moons). A prime landing location would be the jumbled-up surface terrain called the Chaos region, which is thought to be much younger than the average crust. A particularly good target would be the region from which transient water plumes have been detected emanating from the moon’s surface in the past. Here we would expect that water from the deeper Europan ocean is getting close to the moon’s surface.
The findings by Nordheim and his colleagues should swing Europa back to being the top priority for astrobiology missions in the outer Solar System, surpassing Saturn’s moon Enceladus, which recently has received a lot of interest from the scientific community. Europa is the only body in our Solar System where not just microbial life, but conceivably also multicellular complex life, might be present—particularly if hydrothermal vent systems like the “black smokers” on Earth exist on the moon’s ocean floor. And perhaps we could find some of that Europan life, or more likely its traces, very close to the moon’s icy surface.