"Research like this is important because it focuses on questions we can definitively answer, like whether or not Europa is inhabitable," said Curt Niebur, outer planets programme scientist at NASA headquarters in Washington, DC."Once we have those answers, we can tackle the bigger question about life in the ocean beneath Europa's ice shell," he added.
For more than a decade scientists have wondered about the nature of the dark material that coats long, linear fractures and other relatively young geological features on Europa's surface. Its association with young terrains suggests the material has erupted from within Europa.
For this particular research, the scientists tested samples of common salt - sodium chloride along with mixtures of salt and water, in a vacuum chamber at Europa's chilly surface temperature of minus 280 degrees Fahrenheit [minus 173 Celsius]. They then bombarded the salty samples with an electron beam to simulate the intense radiation on the moon's surface.
After a few tens of hours of exposure to this harsh environment, which corresponds to as long as a century on Europa, the salt samples, which were initially white just like table salt, turned a yellowish-brown color similar to features on the icy moon. The researchers found the color of these samples, as measured in their spectra, showed a strong resemblance to the color within fractures on Europa that were imaged by NASA's Galileo mission.
Researchers also find that the longer the samples were exposed to radiation, the darker the resulting color. Scientists could use this type of color variation to determine the ages of geologic features and material ejected from any plumes that might exist on Europa.