Gas giant Jupiter has scores of Moons, the most intriguing of which is Europa. Europa boasts a mysterious liquid water ocean beneath its thick icy shell and NASA’s Hubble Space Telescope has now found Europa’s oceans are intriguingly similar to seas on Earth. The shocking finding has significantly boosted NASA’s chance of finding alien life.
Europa’s subsurface ocean harbours approximately twice as much water as all of Earth’s seas put together and US space agency NASA had believed sulphate salts dominated this watery world.
But Hubble has detected the likely presence of sodium chloride on Europa’s frozen shell, a landmark NASA study reports.
This sodium chloride, commonly known as table salt, probably emanates from the ocean.
This is a significant find, given the saltiness of Earth’s oceans primarily derives from sodium chloride.
Dr Samantha Trumbo, of the Caltech, the NASA study’s lead author, said: “We do need to revisit our understanding of Europa’s surface composition, as well as its internal geochemistry.
“If this sodium chloride is really reflective of the internal composition, then Europa’s ocean might be more Earth-like than we used to think.”
NASA’s Galileo spacecraft, which orbited Jupiter from 1995 through 2003, spotted strange, yellow areas on Europa’s surface.
Subsequent laboratory experiments performed in simulated Europa surface conditions suggest irradiated sodium chloride was responsible for these “colour centres.”
Europa lies within Jupiter’s powerful radiation belts and the moon’s surface is constantly bombarded with the brutal energy.
NASA’s Hubble’s Space Telescope Imaging Spectrograph instrument (STIS) was then tasked with detecting this salt over four observing runs, from May 2017 through August 2017.
STIS spotted an absorption line at 450 nanometers, which is characteristic of irradiated NaCl.
But this signature was not spread evenly over Europa. Instead, NASA found it only on the moon’s leading hemisphere, the side that is constantly facing Jupiter.
Like Earth’s own moon, Europa is tidally locked to its parent planet, always showing it the same face.
In addition, the salt was concentrated in “chaos regions” — complex, disrupted and geologically young areas of the Europan surface where water could well be welling-up from its watery depths.
Europa’s trailing hemisphere is hit by sulphur compounds spewed out by another one of Jupiter’s many moons, the super-volcanic Io.
But Io’s leading hemisphere is shielded from this cosmic rain.
So, the composition of the young, relatively pure leading-hemisphere chaos terrain “may best represent that of Europa’s endogenous material,” Dr Trumbo and her colleagues wrote in the study.
However, it remains unclear if this is definitely the case, Dr Trumbo stressed.
“We are confident that the sodium chloride is coming from the interior,” she said.
“But the extrapolation to ‘the interior is chloride-dominated’ is less certain.”