While movies often show aliens as little green men, real extraterrestrial life—if it exists in our solar system—will likely be microscopic. NASA recently gave microbiologist James Holden $621,000 to study what life on Jupiter’s moon Europa might look like.
His research takes an unexpected approach: studying volcanoes deep in Earth’s oceans.
Europa’s icy surface hides a vast salty ocean, possibly warmed by a molten core. “We think, based on our own planet, that Europa may have conditions that can support life,” says Holden, pointing to Earth’s hydrothermal vents as a model. NASA’s Europa Clipper mission, launching soon, will test how habitable the moon really is.
Holden has studied deep-sea vents since 1988. “I’ve been looking at deep-sea volcanoes since 1988,” he says. “To get our microbes from them, we use submarines—sometimes human-occupied, sometime robotic—to dive a mile below the surface and bring the samples ashore.”
His lab recreates the extreme conditions these microbes thrive in—no light, no oxygen, just chemicals from the vents. Since Europa’s ocean might be similar, Holden believes any life there could resemble these deep-sea organisms.
“We have long had a basic interest in knowing if there is life beyond our planet and how that life would function,” Holden adds.
“It’s exciting to think that the answer to the secret might be here on our own planet.” But Europa isn’t identical to Earth, so its microbes—if they exist—might work differently.
Holden’s research focuses on how alien microbes could generate energy. Earth’s hydrothermal microbes use enzymes called hydrogenases to break down hydrogen, but different types of hydrogenases could produce very different life forms.
Iron, sulfur, and carbon from vents also interact with hydrogen in ways scientists don’t fully understand. “Our research will be to determine how the different chemical process contribute to an organism’s physiology,” says Holden.
If Europa has life, it may not look exactly like Earth’s, but studying our planet’s extremes gives scientists their best clues. As Holden puts it, the key to finding aliens might be hidden in the darkest depths of our own oceans.