Could salt on Jupiter's moon mean life?
By Amanda Jermyn

Far away Jupiter’s moon, Europa, may be exotic in many ways, but recent research shows that it harbors a taste of home – table salt. Formally known as sodium chloride, this is also the stuff that makes our oceans salty.

In research published in Science Advances on June 12th scientists from Caltech and NASA’s Jet Propulsion Laboratory revealed the discovery of large deposits of sodium chloride on Europa’s surface.

Past flybys by the Voyager and Galileo spacecraft revealed that Europa has a liquid water ocean covered by an icy crust. Galileo’s infrared spectrometer, a device used to determine the composition of a surface, showed deposits of what appeared to be magnesium sulfate, found in Epsom salts, on Europa’s surface. However, more recent high resolution infrared data from the Keck Observatory on Mauna Kea suggested that what scientists saw on Europa’s surface was not magnesium sulfate. According to Caltech’s Mike Brown, “We thought we might be seeing sodium chlorides, but they are essentially featureless in an infrared spectrum.” So the researchers decided to look in the visible light spectrum instead. Subsequent observations in visible light using the Hubble Space Telescope did indeed confirm the presence sodium chloride on the surface of Europa.

While we can’t as yet be sure that the salt came from Europa’s subsurface ocean, it is currently the most likely explanation. As Europa’s icy crust shows signs of geological activity, it is thought that the salt likely reached the surface through geysers and upwelling through cracks in the ice.

Finding sodium chloride rather than magnesium sulfate on this moon’s surface suggests that Europa’s subsurface ocean may be more chemically similar to oceans here on Earth than previously thought. According to Caltech graduate student, Samantha Trumbo, lead author on the research, “Magnesium sulfate would simply have leached into the ocean from rocks on the ocean floor, but sodium chloride may indicate that the ocean floor is hydrothermally active. That would mean Europa is a more geologically interesting planetary body than previously believed.”

The hydrothermal vents found in Earth’s oceans are teeming with life, so if Europa too has hydrothermal vents on its ocean floor, this ups the odds of finding life there.

Based on data from the Cassini mission, hydrothermal vents are also suspected to exist on the ocean floor of Saturn’ moon, Enceladus, along with salts and organic molecules. So both Enceladus and Europa should prove promising targets for future space missions in the search for life beyond our planet.

The next mission to Europa will be the European Space Agency’s Jupiter Icy Moon Explorer (JUICE), due to launch in June 2022 and reach Jupiter in October 2029. Its focus will be on studying three of Jupiter’s moons: Ganymede, Callisto and Europa, all of which are thought to have large bodies of water beneath their surfaces, making them potentially habitable environments. Also in the works is NASA’s Europa Clipper, due to launch in June 2023. It is set to study Europa in a series of flybys while in orbit around Jupiter. Its aim is to explore Europa’s habitability and help find a suitable landing site for NASA’s proposed Europa Lander, an astrobiology mission planned to launch in 2025. With these missions in the works the quest for extraterrestrial life continues.

Back here on Earth, Saturday, October 5th is International Observe the Moon Night, so if the night is clear, take the opportunity to go outside and observe this natural wonder in our very own celestial backyard.

Join the Springfield Stars Club on Tuesday, September 24th at 7:00pm at the Springfield Science Museum for a talk by Richard Sanderson on “A look back at Summer Astronomy Events.” Sanderson is the recently retired curator of physical science at the Springfield Science Museum and a long time member of the Springfield Stars Club. He is an astronomy writer and co-author of the 2006 book, “Illustrated Timeline of the Universe.” Refreshments will be served, and the public is welcome. The meeting is free of charge for members, with a suggested donation of $2 per non-member.

Also, on Friday, Oct. 4th at 7:30pm, the Stars Club and the Springfield Science Museum will host “Stars over Springfield,” an astronomy adventure for the whole family. Amateur astronomer Ed Faits will give a talk on “Comets, Asteroids and other Wanderers.” Richard Sanderson will also give a brief talk on the November 11th transit of Mercury. A fee of $3 for adults and $2 for children under 18 will be charged.