Life could have flourished between 3.5 billion and 4.2 billion years ago, which left the earliest evidence of life on earth by 500 million years.
When the planets in our solar system were formed, the frequency and size of the meteorites in the solar system decreased. The gradual decline opened a window where the conditions were right for life to form and remain.
But there are different ideas about when the heavy meteorites ceased. Some scientists believe the planets endured a later bombardment of 3.8 billion years ago.
For the new study, scientists studied the oldest known mineral grains from meteorites that they originally believed came from the southern highlands of Mars. By looking at them at the atomic level, the researchers decided that the minerals were unchanged because they were formed and crystallized near the martian surface.
The grains were compared to areas of the earth and moon affected by meteorites. More than 80% of the mineral grains were changed with extreme pressure and temperature.
The researchers believe that the samples show that heavy meteorites stopped beating Mars before the mineral grains were formed. This means that the marshy surface could have been habitable just around the time when the water was abundant.
"Giant meteorite effects on Mars between 4.2 and 3.5 billion years ago may have actually accelerated the release of early water from the interior of the planet's setting stage for life-forming reactions, "says Desmond Moser, studying author and associate professor at the Western University of Earth Science and Geography, in a statement. "This work can point out good places to get samples returned from Mars."
University Zircon and the Accessory Phase Laboratory, led by Moser, were crucial to the study.
NASA's March 2020 rover, launched next summer, will collect and stow samples on the Mars surface for later missions to return to Earth. Moser hopes that his research could help inform where they can be collected.