Europa and Other Planetary Bodies May Have Extremely Low-Density Surfaces | Planetary Science Institute
http://www.psi.edu/news/press-releases
Spacecraft landing on Jupiter’s moon Europa could see the craft sink due to high surface porosity, research by Planetary Science Institute Senior Scientist Robert Nelson shows.
Nelson was the lead author of a laboratory study of the photopolarimetric properties of bright particles that explain unusual negative polarization behavior at low phase angles
observed for decades in association with atmosphereless bodies including asteroids 44 Nysa, 64 Angelina and the Galilean satellites Io, Europa and Ganymede.
These observations are explained by extremely fine-grained particles with void space greater than about 95 percent. Grain sizes would be on the order of the wavelength of light
of the observations (a fraction of a micron). This corresponds to material that would be less dense than freshly fallen snow, raising questions about the risk of a Europa lander
sinking into the surface of the Jupiter satellite.
This work was published in the journal Icarus and is titled "Laboratory simulations of planetary surfaces: Understanding regolith physical properties from remote photopolarimetric
observations."
Observations were made using a goniometric photopolarimeter of novel design located at Mt. San Antonio College in Walnut, California. The powders used were aluminum oxide
(Al2O3), which is an excellent regolith analog for high albedo airless bodies in the solar system, including water ice bodies such as Europa.
![](http://nautilus.fis.uc.pt/astro/img/ss/jupiter/Europa/PIA00746.jpg)