Does Mars, or did it ever, have life? We still don’t know the answer to that question, but scientists have found new evidence that at least one region had ancient sea-floor hydrothermal activity, a discovery that increases the chances that microbial life may have once existed, and could also provide clues as to how life started on Earth.
The new findings are based on observations by NASA’s Mars Reconnaissance Orbiter (MRO) of a basin in the southern hemisphere called Eridania. The basin contains huge deposits which scientists think were formed by hot water which entered the bottom of a large sea about 3.7 billion years ago. The water was heated by volcanic activity, but today, the volcanoes are no longer active and the sea has long since evaporated.
“Even if we never find evidence that there’s been life on Mars, this site can tell us about the type of environment where life may have begun on Earth,” said Paul Niles of NASA’s Johnson Space Center in Houston. “Volcanic activity combined with standing water provided conditions that were likely similar to conditions that existed on Earth at about the same time – when early life was evolving here.”
This undersea hydrothermal activity would likely have been similar to what still occurs on Earth today, and at about the same time when life is thought to have started here. As such, this sea could have been a “cradle for life” on Mars.
“This site gives us a compelling story for a deep, long-lived sea and a deep-sea hydrothermal environment,” Niles said. “It is evocative of the deep-sea hydrothermal environments on Earth, similar to environments where life might be found on other worlds – life that doesn’t need a nice atmosphere or temperate surface, but just rocks, heat and water.”
There is still much debate as to whether Mars once had a larger ocean in the northern hemisphere, but even a smaller sea could have provided very habitable conditions. This sea is estimated to have contained 50,000 cubic miles (210,000 cubic kilometers) of water, nine times more than all of the Great Lakes on Earth. Minerals found in the deposits by MRO include serpentine, talc and carbonate.
“Ancient, deep-water hydrothermal deposits in Eridania basin represent a new category of astrobiological target on Mars,” according to the report. “Eridania seafloor deposits are not only of interest for Mars exploration, they represent a window into early Earth.”
There is also now evidence for current hydrothermal activity on the bottom of Enceladus’ global subsurface ocean, and perhaps Europa as well, which makes these moons prime targets in the search for life elsewhere in the Solar System.
The new hydrothermal findings add clue to the growing knowledge that Mars was once a very wet place, with rivers, lakes, deltas, seas, groundwater and hot springs.