On Earth, sea salt represents an excellent way to part gullible yuppies from their money. But on Jupiter’s moon Europa, sea salt may mean so much more. In their quest to determine whether the icy moon could support life (now or in the past), NASA made a breakthrough in discovering that Europa had a vast underground ocean. Now, after identifying a dark material coating young geological features, NASA scientists believe that rather than sulfur, it could actually be sea salt.
Why is this important? Because it means the underground sea may be interacting with the ground above. This would be an important factor in whether or not Europa could have ever supported life.
“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,” said 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.”
The dark material has baffled scientists for decades. Based on earlier studies using data from the Galileo spacecraft, scientists first hypothesized that the material was a mixture of sulfur and magnesium. One thing that’s certain is that Europa is under constant bombardment from radiation – it has no atmosphere to speak of, after all. Originating from Jupiter’s magnetic field, electrons and ions slam into Europa at incredible speeds, to the tune of a particle accelerator scientists would use here on Earth. Whatever the substance was, scientists figured, the radiation was sure to have something to do with it.
In order to test their theories, scientists took a novel approach – they created an environment that mimicked Europa’s temperature, near-vacuum and radiation. From there, it was a (somewhat) simple matter of putting materials to the test in the environment and seeing which one looked the most like what they had observed on Europa. In order to do that, they collected spectra (which could be considered chemical fingerprints) encoded in the light reflected by the compounds.
“We call it our ‘Europa in a can,'” said research lead Kevin Hand. “The lab setup mimics conditions on Europa’s surface in terms of temperature, pressure and radiation exposure. The spectra of these materials can then be compared to those collected by spacecraft and telescopes.”
The team exposed different mixtures of salt and water to the environment and left them there for about 30 hours, which would equate to nearly 100 years on Europa. Lo and behold, after exposure the salt compounds were a dark yellowish brown, not unlike what scientists observe on Europa. A spectra analysis confirmed and supported the strong likeness.
“This work tells us the chemical signature of radiation-baked sodium chloride is a compelling match to spacecraft data for Europa’s mystery material,” Hand said.
The longer the samples were exposed, the darker they got, so the researchers believe this experiment could help astronomers date geological features on Europa based on color. Newer technology will be needed to obtain detailed, high-definition color images from Europa in the future.