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takyon [soylentnews.org] writes:

Future Europa [wikipedia.org] landers may be in danger of sinking into a surface [earthsky.org] less dense than freshly fallen snow:

Space scientists have every reason to be fascinated with Jupiter's moon Europa, and, in 2017, NASA and the European Space Agency (ESA) announced they are planning a joint mission to land there [usra.edu]. As the video above explains, this little moon is thought to have a liquid ocean submerged beneath an icy crust. Scientists believe it could host extraterrestrial life [popsci.com]. But Europa's surface is much more alien than any we've ever visited. With its extremely thin atmosphere, low gravity – and a surface temperature of some -350 degrees F. (–176 °C.) – Europa might not be kind to a landing spacecraft. The moon's surface might be unexpectedly hard. Or – as evidenced by a study from the Planetary Science Institute announced on January 24, 2018 – Europa's surface might be so porous that any craft trying to land would simply sink.

The study – published in the peer-reviewed [elsevier.com] journal Icarus – comes from scientist Robert Nelson [psi.edu]. If you're a student of space history, its results might sound familiar. Nelson pointed out in his statement [psi.edu]:

Of course, before the landing of the Luna 2 robotic spacecraft in 1959, there was concern that the moon might be covered in low density dust into which any future astronauts might sink.

Now Europa is the source of a similar scariness, with Nelson's study showing that Europa's surface could be as much as 95 percent porous.

Laboratory simulations of planetary surfaces: Understanding regolith physical properties from remote photopolarimetric observations [sciencedirect.com] (DOI: 10.1016/j.icarus.2017.11.021) (DX [doi.org])

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