NASA's 'Europa in a can' experiment, as dubbed by research lead Kevin Hand, showed that salt samples turned a yellow-brown colour after exposure to conditions similar to those found on the moon. Credit: NASA/JPL-Caltech
Dark material on Jupiter’s moon Europa could be sea salt from an underground ocean that has been discoloured by radiation, according to an experiment carried out at NASA’s Jet Propulsion Laboratory (JPL) in Pasadena, California.
If true, the revelation could increase the likelihood that Europa is able to support life.
Scientists at JPL put table salt, and other samples of salt and water, in a vacuum chamber mimicking Europa’s surface temperature of minus 173°C.
They then bombarded these samples with an electron beam to simulate the radiation on Europa’s surface.
After tens of hours of exposure, the samples turned from white to yellow-brown, resembling the colours seen in fractures on Europa imaged by NASA’s Galileo mission.
The experiment found that, the longer the salt was exposed to the electron beam, the darker the colour.
"This work tells us the chemical signature of radiation-baked sodium chloride is a compelling match to spacecraft data for Europa's mystery material," says research lead Kevin Hand, a planetary scientist at JPL.
For over a decade, scientists have pondered over the dark material on Europa, which coats long, linear fractures and other geological features on the moon’s surface.
"If it's just salt from the ocean below, that would be a simple and elegant solution for what the dark, mysterious material is," Hand says.
While this latest research provides a tantalising answer as to the mystery substance on Europa, it cannot be confirmed, as no telescope on Earth can observe the moon in a high enough resolution to reach a definitive conclusion. NASA researchers say this could be achieved during future missions by using a spacecraft to observe the moon.
"We have many questions about Europa, the most important and most difficult to answer being ‘is there life?’
Research like this is important because it focuses on questions we can definitively answer, like whether or not Europa is inhabitable," says Curt Niebur, Outer Planets Program scientist at NASA Headquarters in Washington.
"Once we have those answers, we can tackle the bigger question about life in the ocean beneath Europa's ice shell."