Searching for Life’s Simple Necessities Across the Asteroid Belt
NASA’s Europa Clipper mission will explore the characteristics of Jupiter’s moon Europa. Its data will help scientists assess if the icy body has the potential to host life.
A previous satellite mission indicated the likely existence of a salty global ocean beneath Europa's ice, potentially holding more water than all of Earth's surface.
One of Clipper’s objectives is to confirm the existence of this subsurface ocean and determine its depth, salinity, and composition, shedding light on whether the moon is a possible place to find life and what type of life could be found. The average salinity of an ocean on Earth is three and a half percent, but in colder regions of the planet, for water to remain liquid, the salt content is higher—in some cases, up to 24 percent. Against expectations, researchers found cold-loving microbes, dubbed cryophiles, living in these conditions.
“If you are a cryophile, it means that you also have to be a salt loving organism,” explained Professor Lyle Whyte, a microbial ecologist at McGill University's Department of Natural Resource Sciences, who is not affiliated with the Europa Clipper mission. As Canada Research Chair (Tier 1) in Polar Microbiology, Whyte studies microbes that live in regions of the High Arctic and in Antarctica. “It’s not like a lush, green Amazon jungle of microbial life. It’s more like a desert of microbial life, but there’s life there,” he told The Scientist for their article on the mission.
Unlike much of life on terrestrial Earth, cryophiles do not use sunlight or sugars to obtain energy. Instead, these organisms produce energy from methane or fix carbon dioxide with the help of sulfur species. This may make these organisms excellent models for the possible types of life on a world like Europa. “If you’re looking for life on the icy moons or Mars, what would Mars or an icy moon microbe look like?” Whyte asked. “It’d have to be a cryophile and highly salt tolerant and anaerobic.”
Recent studies suggest there may also be plumes of water vapor erupting on Europa. Analyses of such plumes on Saturn’s icy moon, Enceladus, suggested the presence of hydrothermal vents. Detecting the compounds present in the plumes might also indicate a cozy home for a cryophile hiding under the icy crust. “When I looked at the list [from the Enceladus plume], I said, ‘Geez, you could put that into a beaker and add some bugs from the Canadian High Arctic, and something would grow on that stuff,’” Whyte said.
