Jupiter's icy moon Europa is a prime candidate for life beyond Earth due to the presence of a deep salty ocean underneath its frozen surface. But finding evidence of life on the surface might be difficult due to a phenomenon called impact gardening.
The surface of airless solar system bodies experiences a constant stream of small impacts. For Europa, there’s the addition of high-energy electrons accelerated by Jupiter’s incredible magnetic field slamming into its surface. This impact gardening has been known for a while but new work, published in Nature Astronomy, has determined how deep into the surface this effect goes.
The research suggests that gardening has churned the top 30 centimeters (11.8 inches) of the moon’s surface over tens of millions of years. Any chemical signs of life, the so-called biosignatures, if present on the surface would be affected.
“If we hope to find pristine, chemical biosignatures, we will have to look below the zone where impacts have been gardening,” lead author Emily Costello, a planetary research scientist at the University of Hawaii at Manoa, said in a statement. “Chemical biosignatures in areas shallower than that zone may have been exposed to destructive radiation.”
The study is the first to recognize the effects of the secondary impacts. These are produced by the debris released by original impacts, falling back down some distance away. While seeing biosignatures on the surface might be very difficult, it might not be impossible to find them. The work suggests that morphological image crates and regions at the mid-to-high latitudes might be affected by impact gardening less.
“This work broadens our understanding of the fundamental processes on surfaces across the solar system,” said Cynthia Phillips, a Europa scientist at NASA’s Jet Propulsion Laboratory in Southern California and a co-author of the study. “If we want to understand the physical characteristics and how planets in general evolve, we need to understand the role impact gardening has in reshaping them.”
This work is going to be important to inform the investigations of upcoming missions such as NASA’s Europa Clipper and the European Space Agency (ESA)’s JUICE mission. The missions will expand our understanding of Europa and beyond. Being able to potentially see biosignatures from orbit would be momentous for these missions.
The ESA mission is expected to launch next June and be in orbit around Jupiter in 2029. Europa Clipper will follow in 2024, reaching the gas giant planet and its moons about six years later.
