Eridania Basin
This view of a portion of the Eridania region of southern Mars shows fractured, dismembered blocks of deep-basin deposits that have been surrounded and partially buried by younger volcanic deposits. The image was taken by the Context Camera on NASA's Mars Reconnaissance Orbiter. NASA/JPL-Caltech/MSSS

“Where did we come from?” is one of those questions whose answer has routinely evaded the philosophically-minded ever since the human mind became capable of thinking in a philosophical fashion. The advent of modern science, which shares some interests with philosophy, has settled that question — we evolved right here on Earth — but there is still uncertainty on whether the seeds of life itself sprung up on the planet itself or were brought in from outside by meteors and asteroids.

Our neighboring planet, Mars, may not have had any life on it at any point in its history — we have no evidence to suggest otherwise — but it still had conditions billions of years ago that were similar to Earth at the time, conditions that led to life flourishing here. And since the geology of Earth has changed dramatically since then, looking at Mars may offer clues about the origin of life on Earth.

NASA’s Mars Reconnaissance Orbiter (MRO) spacecraft has been circling the red planet since March 2006, and it found large hydrothermal deposits in the Eridania basin — a region in southern Mars that was once filled by a sea with about 50,000 cubic miles of water and now has some of the oldest exposed rocks on the planet’s surface. The deposits, which have been attributed to seafloor hydrothermal activity, are estimated to be about 3.7 billion years old.

Researchers used data from MRO’s Compact Reconnaissance Spectrometer for Mars instrument to identify the minerals in those deposits. “The mix of minerals identified from the spectrometer data, including serpentine, talc and carbonate, and the shape and texture of the thick bedrock layers, led to identifying possible seafloor hydrothermal deposits. The area has lava flows that post-date the disappearance of the sea. The researchers cite these as evidence that this is an area of Mars' crust with a volcanic susceptibility that also could have produced effects earlier, when the sea was present,” according to a statement Friday on NASA’s website.

The combination of volcanoes and standing water that led to hydrothermal conditions on Earth at around the same time is a likely candidate for where and how life began on our planet, but since Earth has an active crust that changes over time, any direct geological evidence from billions of years ago is now lost. The availability of exposed crust from that time on Mars, which likely had similar conditions at the time, is what has excited the researchers.

Mars Hydrothermal Activity
This diagram illustrates an interpretation for the origin of some deposits in the Eridania basin of southern Mars as resulting from seafloor hydrothermal activity more than 3 billion years ago.The ground level depicted is an exaggerated topography of a transect about 280 miles long. Blue portions of the diagram depict water-depth estimates and the possibility of ice covering the ancient sea. NASA

“This site gives us a compelling story for a deep, long-lived sea and a deep-sea hydrothermal environment. 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,” Paul Niles of NASA’s Johnson Space Center, Houston, and a co-author of a research paper on the topic, said in the statement.

Earth also has life forms that exist without sunlight and can derive energy from rocks, but that still doesn’t tell us much about the environmental conditions on Earth when life started here. And subsurface hydrothermal activity on some moons of Jupiter and Saturn — Europa and Enceladus respectively — make them candidates both for finding extraterrestrial life and for human habitability.

Titled “Ancient hydrothermal seafloor deposits in Eridania basin on Mars,” the open-access paper was published online July 10 in the journal Nature Communications.