Iron-bearing rocks found near ancient Mars seaport sites could provide important clues as to whether life once existed on the Red Planet, according to Journal of Geophysical Research . An international research team led by scientists at the University of Edinburgh suggests that these strata of rock should be the main targets of future missions – such as NASA's Mars 2020 Rover – looking for signs of life. This life, if it exists, will probably take the form of tiny microbes, the scientists think.
The rocks in question formed between three and four billion years ago at the bottom of ancient lake beds, when the Martian surface was plentiful in the water and the climate was warmer. They are composed of compacted clay and clay, but are also rich in iron and silicic acid, which can contribute to the conservation of fossils.
The rocks themselves are better preserved than those of a similar age on Earth, because the Martian crust has no plates like those on our planet. On Earth, these plates move, a process that can destroy rocks and their fossils.
For their study, the scientists produced an overview of fossil recordings on Earth and examined the results of experiments that reproduced the conditions on Mars and data from previous Mars missions.
"We are using current results from research into Earth's fossil and fossilization processes and the geological exploration of Mars by rovers and orbiters to select the most preferred targets for astrobiological missions to Mars," the authors wrote in the study.
"We conclude that siliceous and ferrous clay clays currently offer the best hope for finding fossils on Mars and should be given priority.
The results could help future missions identify landing sites and the best locations to collect rock samples.
"There are many interesting rock and mineral deposits on Mars where we would look for fossils, but since we can not send rovers to all, we have tried to prioritize the most promising deposits according to the best available information," Sean McMahon from the School of Physics and Astronomy at Edinburgh University said in a statement.