These Mars Rocks Could Hold Vital Clues to Life On the Red Planet

The Jezero Crater delta, a well-preserved ancient river delta on Mars. NASA/JPL-Caltech/MSSS/JHU-APL

Iron-rich rocks found near ancient lake sites on Mars could hold vital clues as to whether life once existed on the Red Planet, according to new research published in the Journal of Geophysical Research.

An international team of researchers, led by scientists from the University of Edinburgh, suggest that these rocks should be prime targets for upcoming missions—such as NASA's Mars 2020 rover—which are designed to search for signs of life. This life, if it exists, will likely take the form of tiny microbes, scientists think.

The rocks in question formed at the bottom of ancient lake beds between three and four billion years ago, when the Martian surface was abundant in water and its climate was warmer. They are made of compacted mud and clay, while also being rich in iron and silica, which can help to preserve fossils.

The rocks themselves are better preserved than those of a similar age on Earth because Mars' crust does not feature plates, like those found on our planet. On Earth these plates move around, a process which can destroy rocks and the fossils inside them.

For their study, the scientists conducted a review of papers investigating fossils on Earth, while also examining the findings of experiments that replicated conditions on Mars and data collected from previous Mars missions.

"We apply recent results from the study of Earth's fossil record and fossilization processes, and from the geological exploration of Mars by rovers and orbiters, in order to select the most favoured targets for astrobiological missions to Mars," the authors wrote in the study.

"We conclude that mudstones rich in silica and iron‐bearing clays currently offer the best hope of finding fossils on Mars and should be prioritized, but that several other options warrant further research."

The findings could help future missions identify landing sites and the prime locations to gather rock samples.

"There are many interesting rock and mineral outcrops on Mars where we would like to search for fossils, but since we can't send rovers to all of them we have tried to prioritise the most promising deposits based on the best available information," Sean McMahon from the University of Edinburgh's School of Physics and Astronomy, said in a statement.