If life ever existed on Mars, then newly discovered mineral deposits on the flanks of a long-dead volcano would be a good place to dig for its remains.
Spotted by a high-powered orbital imager, they’re not the first deposits found on Mars of silica, a mineral used by some simple forms of life, including single-celled algae that evolved early in Earth’s volcanic past.
But the new deposits are the first from a locale with a definite volcanic pedigree, formerly rich in heat and water, as well as minerals — a locale formerly suited, by any earthly definition, for life.
Stand on the slopes of Nili Patera 3.7 billion years ago, and “you would see steam rising up out of the volcano. In the spots we see the deposits, that’s where the highest concentration of steam would be,” said geoscientist Jack Mustard of Brown University. “It’d be like standing on Hawaii, looking across a volcano, seeing the fumaroles where vapors are given off, or standing in Iceland where the hills are steaming.”
Mustard’s findings, co-authored with fellow Brown geoscientist J.R. Skok, were published October 31 in Nature Geoscience. His laboratory is among those that in recent years has processed an extraordinary flow of red planet data, returned by Mars-orbiting spacecraft and surface-exploring robots.
This data has moved researchers beyond looking for signs of water — the latest of which was reported just last week, by both the Spirit and Phoenix rovers — to evaluating potentially once-habitable environments in precise detail.
“It’s the most definitive hydrothermal system we’ve found on Mars. You can see the source of the heat, the driving of the fluids that left the deposits,” said Mustard. “In this deposit, you have the culprit right before you. In other deposits, they’re either sedimentary, or in the center of an impact crater. You have no idea how they happened.”
According to Mustard, traces of any organisms that existed could still be found in the silica, which is non-porous and ideal for preserving fossil remains from the ravages of time and weather. Even after 3.7 billion years, any degradation would come only from silica-penetrating cosmic rays. Those break down biological compounds, but would still leave telltale residues of carbon.
The ExoMars expedition robot, scheduled to launch in 2018, will be equipped with a six-foot-long drill perfect for digging beneath ray-damaged layers.
Mustard isn’t yet prepared to say the rover Curiosity, successor to the Phoenix and Spirit rovers, should visit Nili Patera when it lands on Mars in 2012. Curiosity lacks ExoMars’ planned drilling capacity, and already has a wealth of places to explore: the ancient lake deposits of Holden crater, a stack of sedimentary layers three miles thick in Gale crater, and the Mawrth Vallis river valley.
But Mustard couldn’t help but speculate. “It would be pretty intriguing” if Curiosity found carbon amidst the silica, he said. “Or the rover, as it’s going up the slopes, could dislodge some rocks and look underneath. That’s where the good stuff is.”
Images: The Nili Patera caldera./NASA, JPL-Caltech, MSSS, JHU-APL, Brown University.
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