Jupiter's moon Europa and Saturn's moon Enceladus may have porous surfaces

Soft surfaces could pose problems for landers planned for the 2020s and 2030s.
By Laurel Kornfeld | Feb 02, 2018
Jupiter's moon Europa and Saturn's moon Enceladus, both of which could host microbial life in their subsurface oceans, may have low-density porous surfaces too soft to support robotic landers.

In a new study, scientists used aluminum oxide to simulate regolith, the layer of rock and dust found on the surfaces of bright solar system bodies that do not have atmospheres.

They studied the samples of aluminum oxide with a photopolarimeter, an instrument used to measure the intensity and polarization of reflected light, at California's Mt. San Antonio College, and found them to be less dense than newly-fallen snow.

Robert M. Nelson, Senior Scientist at the Planetary Science Institute (PSI) led the study, whose participants included scientists from various universities as well as NASA's Jet Propulsion Laboratory (JPL) in California and the California Polytechnic State University at Pomona.

While both moons may have soft surfaces composed of low-density ice particles, they could still have solid outer shells. If this is the case, landers would set down on a solid surface covered by a thin layer of snow.

If the low density surface ice particles come from subsurface ocean plumes, they may contain the organic compounds necessary for life the landers were sent to find.

In a press release, Nelson noted there were similar concerns that the 1959 Luna 2 robotic Moon lander would sink into a possible surface layer of lunar dust.

Observations of distant objects in visible wavelengths cannot look beyond "the outermost microns of the surface," he added. A micron is a unit of length equal to one-millionth of a meter.

Within its first five months of operation, the James Webb Space Telescope (JWST), which will be equipped with spectroscopic and near-infrared instruments, will study the thermal and atmospheric structures of Europa and Enceladus and look for evidence of plumes on both.

Before any landers visit these moons and take samples of their ices, both worlds will be studied by flyby missions such as the European Space Agency's (ESA) Europa Clipper.

Findings of the study were published in the journal Icarus.





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