Curtin university scientists leading proposed mission to Mars to find signs of extraterrestrial life

Perth-based scientists have uncovered evidence of ancient hot water activity on Mars, revealing the planet may have been habitable in its past. The Curtin University-led team made the exciting discovery in a 4.45 billion-year-old zircon grain from a Martian meteorite found in the Sahara Desert in 2011. Using nano-scale imaging and spectroscopy, the researchers found geochemical “fingerprints” of water-rich fluids in the grain. “Hydrothermal systems were essential for the development of life on Earth and our findings suggest Mars also had water, a key ingredient for habitable environments, during the earliest history of crust formation (on the planet),” study co-author Dr Aaron Cavosie, from Curtin’s School of Earth and Planetary Sciences, said. Curtin researchers are also playing key roles in a proposed mission to Mars to collect and return samples of ancient hot spring deposits previously identified by NASA’s Spirit Rover in the Columbia Hills of Gusev Crater. “Our research suggests that the Columbia Hills hot spring materials represent humanity’s best chance to search for extraterrestrial life,” the LifeSprings Mars website claims. The head of Curtin’s School of Earth and Planetary Sciences, Professor Martin Van Kranendonk, is the program manager for LifeSprings Mars, a multinational team consisting of Australian, NASA, the European Space Agency, and Japanese and New Zealand scientists with expertise in Mars geology. In June last year, Professor Van Kranendonk led members from NASA’s Mars Exploration Program, the European Space Agency, the Australian Space Agency, and CSIRO on a field expedition to the Pilbara to see ancient stromatolite fossils that are 2.7 to 3.5 billion years old. The most ancient of these fossils are considered the oldest, most convincing evidence of life on Earth. They’re helping planetary scientists understand what to look for and where in the search for life on Mars. Dr Cavosie said the discovery from the zircon grain was older than the hydrothermal rocks that the LifeSprings Mars mission was targeting. Its own story was fascinating. “It’s about half the size of a human hair,” he said. “If you go to the beach in Perth, anywhere, there’s lots of zircons amongst the sand, so it’s not an uncommon mineral. What isn’t common about this zircon is it’s exquisitely old. It’s older than anything that’s ever been dated on Earth. “When you study material like that, anything you find about those materials can be attached to that time period of Martian history. These zircons provide an amazing window into the earliest history of Mars.” The Curtin researchers were given a small slice of the Martian meteorite, nicknamed Black Beauty. “It’s a special meteorite,” Dr Cavosie said. “Most meteorites from Mars are igneous rocks, not very different than we have on Earth, aside from the fact they’re from Mars. Those rocks would have formed at a time period of melting and igneous activity on Mars, and they were later blasted off to Earth. “They’re not as old as the materials in Black Beauty ... It’s a piece of the Martian surface that they call regolith ... It’s all of the material on the surface that consists of sand and rocks and broken up fragments and a whole bunch of muck stuck together. “If this gets buried, which it did on Mars, ultimately it gets hard and it becomes a rock. When you cut open and get a little slice of Black Beauty, it’s just a buffet of a whole bunch of different things, lots of little rock fragments, lots of little mineral fragments, all kind of glued together with crushed up rock and mineral between them. “The slice that we got had quite a few zircons that were exposed. (The zircon we focused on) was different and unique from all of the others in this meteorite. “The first thing we did was determine its age ... we realised it was quite old, at 4.45 billion years. So that got our attention.” They then discovered evidence of the zircon being hit by a meteorite impact. “We call these shocked zircons, because we can see evidence that the shock wave from a meteorite impact event changed the zircon in small ways. So, we thought, well, that’s very exciting,” Dr Cavosie added. It was the first shocked zircon ever found from Mars. Zircon only has three elements in it: oxygen, silicon and zirconium. But this zircon had trace elements the scientists weren’t expecting to find. These included iron, aluminium and sodium. “These elements have been reported from some zircons, but normally they’re only found in zircons that are really fractured and broken ... However, in this case, that wasn’t the story. We found that these elements defined beautiful patterns, kind of like the layers in an onion around this zircon,” Dr Cavosie said. “When you see that type of element pattern, it tells you that they got incorporated in the zircon when it’s formed from magma. Normally, igneous crystalline zircons don’t have iron, aluminium and sodium. Those elements normally aren’t permitted into zircon like that. So we said, ‘Well, that’s really funny’. This zircon is wonderfully crystalline. It’s absolutely spectacular and it’s in great condition. “It has been hit by a meteorite, but that doesn’t create the types of damage that lets all these elements in. What’s going on here?” After more detective work they found out the closest match to their zircon was zircons found in granite at Olympic Dam in South Australia, where uranium, copper, silver and gold is mined. A study into these granites five years ago by one of the study co-authors found they had hydrothermal systems going through them. “They had the same type of element zoning that we found in the Martian zircon, with the same elements. We really had to do a double take because the data were so similar to what we saw in the Martian zircon that we said, ‘Oh, my goodness’,” Dr Cavosie said. “These elements are a signature of what happens when hot water is present, when these zircons are forming and hot water is the hydrothermal system. “We found our answer on Earth, interestingly enough, and it happened to be from a from a magmatic, hydrothermal, ore deposit in South Australia, which is really interesting.” Dr Cavosie, a geologist, geochemist and planetary scientist, said the study findings provided avenues for further research. “We’re going to examine more zircons to see if we can continue to develop the story. But the bigger picture here is that we documented that there were hydrothermal systems present at this very early time period in the Martian crust and that’s one key ingredient that’s important for habitability,” he said. Even more tantalising is the dream of bringing hydrothermal rocks from the surface of Mars back to WA to investigate, courtesy of the LifeSprings Mars mission.