The surface of Jupiter’s moon Europa is swayed by small impacts – its conditions may currently be suitable for life

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NASA’s Galileo spacecraft captured this colorful view of Jupiter’s moon Europa in the late 1990s. Scientists study the processes affecting the surface as they prepare to explore the icy body. Credit: NASA/JPL-Caltech/SETI Institute

Jupiter’s moon Europa and its global surroundings may have conditions suitable for life right now. Scientists study processes at the icy surface as they prepare for exploration.

It’s easy to see the impact of space debris on our moon, where the old, broken surface is covered in craters and scars. Europa, the icy moon of Jupiter, withstands a similar defeat – along with extremely intense radiation. When the icy moon’s upper surface undulates, material brought to the surface is emitted by high-energy electronic radiation accelerated by Jupiter.

NASA-funded scientists are studying the cumulative effects of small impacts on Europa’s surface as they prepare to explore the distant moon with the Europa Clipper mission and examining prospects for a future landing mission. Europa is of particular scientific interest because its salty ocean, which lies beneath a thick layer of ice, may currently have conditions suitable for current life. This water may make its way to the ice crust and onto the moon’s surface.

New research and modeling estimates the extent of the disturbance on this surface through a process called the “horticultural effect.” The work, published July 12 in Nature Astronomy, estimates that Europa’s surface was affected by impacts as small to medium depths of about 12 inches (30 cm) over tens of millions of years. And any molecules that could be considered as potential biosignatures, which include chemical signs of life, could be affected at this depth.

In this enlarged image of Europa’s surface, taken by NASA’s Galileo mission, the thin, bright layer, visible over a cliff in the middle, shows the type of areas affected by the horticultural effect. Credit: NASA/JPL-Caltech

This is because the effects will cause some of the material to move to the surface, where the radiation will likely break the bonds of any potentially sensitive, large molecules generated by biology. Meanwhile, some of the material on the surface will be pushed down, where it can mix with what’s below the surface.

“If we are to hope to find pure biochemical signatures, we will have to look below the region where the horticultural impacts were,” said lead researcher Emily Costello, a planetary research scientist at the University of Hawaii at Manoa. “Biochemical fingerprints in shallow areas of that region may have been exposed to devastating radiation.”

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While it has long been understood that the horticultural impact likely occurs on Europe and other airless bodies in the Solar System, the new modeling provides the most comprehensive picture yet of the process. In fact, it is the first to take into account secondary effects caused by debris falling on Europa’s surface after a primary impact kicked it. The research shows that the middle to high latitudes of Europe will be less affected by the double whammy of the effect of horticulture and radiation.

“This work expands our understanding of fundamental processes at surfaces across the solar system,” said Cynthia Phillips, a Europe scientist at NASA’s Jet Propulsion Laboratory in Southern California and co-author of the study. “If we want to understand the physical properties and how planets generally evolve, we need to understand the role that horticulture plays in reshaping them.”

The Europa Clipper, which is operated by JPL for NASA, will help advance this understanding. The spacecraft, which is targeted for launch in 2024, will make a series of flights close to Europa as it orbits Jupiter. It will carry instruments to precisely survey the moon, as well as take samples of dust and gases that are kicked above the surface.

More about the mission

Missions like the Europa Clipper contribute to the field of astrobiology, the interdisciplinary research on variables and conditions in distant worlds that could harbor life as we know it. While the Europa Clipper is not a life-detecting mission, it will conduct a detailed survey of Europa and check whether the icy moon, with its subsurface ocean, has the potential to support life. Understanding the habitability of Europe will help scientists better understand how life evolved on Earth and the possibility of finding life outside our planet.

The Jet Propulsion Laboratory, operated by the California Institute of Technology in Pasadena, California, directs the Europa Clipper mission development in partnership with APL for NASA’s Science Mission Directorate in Washington. The Planetary Missions Program Office at NASA’s Marshall Space Flight Center in Huntsville, Alabama, manages the Europa Clipper mission program.

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