Jupiter’s moon Europa has an icy crust, under which lies an entire ocean. However, a new study suggests that its surface might be extremely porous.

In 2017, NASA and the European Space Agency (ESA) announced they are planning a joint mission to land in Europa. Scientists believe it could host extraterrestrial life.

NASA wants to send a spacecraft to orbit Europa, shown here with Jupiter not to scale, sometime in the 2020s. Credit: NASA/JPL-CALTECH

NASA is developing a flyby mission to the icy moon. They might launch it sometime in the 2020s. Nasa calls this probe, the Europa Clipper. It will study the satellite’s buried ocean and assess its habitability using a variety of instruments.

Congress has pushed NASA to also get a lander down on Europa. The agency’s current thinking calls for launching a surface probe separate from Clipper.

However,  the surface of Saturn’s moon might be stranger than we thought.

The Discovery

Study team members measured the reflectance properties of various configurations of aluminum oxide powder. A good analogy, they said, for the material on the surface of bright, airless bodies such as Europa, which harbors an ocean of liquid water beneath its icy shell.

So, they discovered that powder composed of very small particles with lots of space between them — material less dense than freshly fallen snow, team members said — shared several key reflectance characteristics with the actual Europan surface.

“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,” lead author Robert Nelson, a senior scientist at the Planetary Science Institute in Tucson, Arizona, said in a statement. “However, we must keep in mind that remote visible-wavelength observations of objects like Europa are only probing the outermost microns of the surface.”

Nelson’s study shows that Europa’s surface could be as much as 95 percent porous.

Nelson’s study of Europa is part of a group of studies he has conducted of both asteroids (44 Nysa, 64 Angelina) and Jovian moons (Io, Europa, Ganymede). He conducts his studies via photopolarimetry, the measurement of the intensity and polarization of reflected light.

So, NASA may need to figure out a way to avoid sinking straight down into the moon’s interior.

The new study appears in the March 1 issue of the journal Icarus.

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Thumbnail image: The Surface of Europa. Credit: NASA, JPL-Caltech, SETI Institute