Mars, a NASA scientist said, is a good place to search for a geological record of life.
But Europa, one of Jupiter’s moons, and the subject of an infrared spectroscopy study using images from Keck Observatory, is the best place in the solar system to look for “living life,” says Kevin Hand, deputy chief scientist for solar system exploration at NASA’s Jet Propulsion Laboratory in Pasadena, Calif.
“Europa is the world that has a liquid water ocean,” Hand said Friday, after publishing a paper on his discovery of hydrogen peroxide on Europa’s surface. Hydrogen peroxide can dissolve in water to form oxygen. “Life needs energy from the sun or chemical energy on Earth.”
Plants convert sunlight into energy via photosynthesis. Scientists have found life — larger than just microbial creatures — in deep ocean waters, near hydrothermal vents, where there is no sunlight. Those creatures use the components coming out of the vents to combine with chemicals in the water to create energy, Hand said. But to survive, larger creatures need oxygen, which is introduced to the water at the surface level, through photosynthesis.
Europa’s oceans are under ice sheets up to 10 kilometers thick, which means sunlight isn’t getting through. But if the hydrogen peroxide settles through the ice, the planet does show evidence of having hydrothermal vents, where Europan versions of squid, jellyfish and tube worms could be living in deep water, he said.
“Don’t get me wrong, discovering microbes on Europa would be amazing,” Hand said.
But finding larger creatures would be even better.
What will it take to find out for sure?
“What we need is a dedicated program of exploration,” he said. “Mars has a dedicated program. Europa doesn’t have that.”
Right now, NASA is developing the Europa Clipper, a mission to travel by the moon.
“Eventually, we want to land and investigate the ocean directly,” he said.
According to Keck officials, NASA’s Galileo mission first detected hydrogen peroxide on Europa when it explored the Jupiter system from 1995 to 2003. Keck’s data shows that peroxide is widespread across Europa’s surface, with the highest concentrations in regions where the ice is nearly pure water. Radiation creates the peroxide.
“The Galileo measurements gave us tantalizing hints of what might be happening all over the surface of Europa, and we’ve now been able to quantify that with our Keck telescope observations,” Caltech astronomy professor Mike Brown said in a written statement. “What we still don’t know is how the surface and the ocean mix, which would provide a mechanism for any life to use the peroxide.”
Brown co-authored the paper on the discovery with Hand.
Europa’s peroxide is believed to be about 20 times more diluted than the hydrogen peroxide mixture available at drug stores, Keck officials said.