Ancient Mars May Have Vented Just Like Earth

This view of a portion of the Eridania region of Mars shows blocks of deep-basin deposits (lighter patches) that have been surrounded and partially buried by younger, dark volcanic deposits. The basin which lies in a region with some of the Red Planet’s most ancient exposed crust. Credit: NASA/JPL-Caltech/MSSS

Did Mars have black and white smokers, too? Scientists have found evidence for ancient sea-floor hydrothermal deposits on Mars that may provide clues about the origin of life on Earth.

Photos taken by NASA’s Mars Reconnaissance Orbiter (MRO) show massive deposits in the Eridania basin in southern Mars that the authors of a recent paper  think are layers of material formed by heated water from volcanic activity. The material would have been deposited at the bottom of a large sea via deep-sea vents 3.7 billion years ago. Hydrothermal activity occurs when water seeps through cracks in the seafloor, gets heated by lava at great depth and then rises back up and gushes into the cold ocean bottom. The water returns laden with minerals which are deposited around the vent.

The Eridania basin of southern Mars is believed to have held a sea about 3.7 billion years ago, with seafloor deposits likely resulting from underwater hydrothermal activity. The map is color-coded for depth, with red showing a depth of about 300 feet (100 meters) to black, more than 10 times that depth. The map covers an area about 530 miles (850 km) wide. Credit: NASA/JPL-Caltech/MSSS

“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. “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 diagram illustrates how some deposits in the Eridania basin of southern Mars may have formed from hydrothermal activity. Credit: NASA

MRO identified serpentine, talc and carbonate — all minerals associated with water — in the basin as well as telltale shapes and textures in the bedrock that hinted at possible seafloor deposits.  Lava flows are there, too, a sign that the region could have been volcanically-active in the distant past when the deposits were put down. 21st century Mars has neither standing water nor volcanic activity, yet the closer we look at Mars, the more evidence of water we see: rivers, lakes, deltas, seas and hot springs and now potential seafloor deposits.

What’s fascinating is the age of the deposits — about 3.7 billion years. Undersea hydrothermal conditions on Earth at about that same time are a strong candidate for where and when life on the planet began. Earth still bubbles and broils with active hydrothermal vents (see photo below), where many forms of life thrive on chemical energy extracted from rocks, without sunlight.

Mineral-rich “white smokers” stream from a hydrothermal vent on the ocean floor. Both black and white smokers provide the  minerals needed for basic life forms to survive without sunlight. Bacteria convert the materials into food. Other living things  feed on the bacteria, helping to build a self-contained ecosystem at the bottom of the deep ocean, where it’s as dark as night. Credit: Wikipedia

“This site gives us a compelling story for a deep, long-lived sea and a deep-sea hydrothermal environment,” said co-author Paul Niles. “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.”

The researchers estimate the ancient Eridania sea held about 50,000 cubic miles (210,000 cubic km) of water. That’s as much as all other lakes and seas on ancient Mars combined and about nine times more than the combined volume of all of North America’s Great Lakes. Eridania’s well-preserved seafloor deposits represent a window into early Earth where similar ancient deposits are poorly preserved. Perhaps Eridania will help us understand how life began on our planet even if it never did on Mars.