Mars 2020 rover
This artist's concept depicts NASA's Mars 2020 rover on the surface of MarsNASA/JPL-Caltech

Rocks near ancient lake sites on Mars suggest that life could have briefly appeared on the red planet about 4 billion years back. Rocks in lake beds are also the best place to look for fossil evidence of past life, according to researchers. 

A new study conducted on finding where the right place to look for life on Mars, if there was any, to begin with, points at sites near where water liquid water once existed, notes a report by The search for life on Mars begins with looking for primitive forms of life like microbes that scientists believed existed on the red planet 4 billion years ago, soon after the solar system came to be.

Sedimentary rocks, rocks that are formed over time when layers of minerals get packed up and compacted- they are like files, trapping, preserving, and fossilising whatever may fall between them. Rocks that are made of mud and clay are the most likely candidates, notes the report. Such rocks are rich in iron and silica which preserve fossils, and Martian lakes are seemingly best place to start. 

Such rocks reportedly formed during the Martian Noachian and Hesperian Periods- between three and four billion years ago. During this time, the planet had an abundant supply of liquid water, so life on Mars was a real possibility then.

Mars' sedimentary rocks are in a better position to preserve fossils because the planet does not experience plate tectonics, notes the report. Tectonics are known as the movement of huge slabs of rock just below the surface and part of the crust that sits atop the soft mantle of planets. This can, over time destroy rocks and by extension, fossils that might be preserved inside them.

Researchers went through existing fossil studies on Earth and results of experiments simulating Mars conditions and they were able to identify sites on the red planet to search for any remaining traces of ancient life that might have existed in the far past.

According to the report, these new findings could help NASA's next rover mission, in terms of where to land and what to look for on Mars, the mission will focus on searching for evidence life from the past. The space agency's Mars 2020 rover is set to collect rock samples which will then be brought back to Earth for analysis by a future mission.

The study was first published in the Journal of Geophysical Research.