According to new research, Mars had the organic molecules necessary for life to emerge around 4.5 billion years ago. And while these critical components may have hitched a ride to Earth around the same time, it was on the Red Planet that life found the most hospitable conditions.
Both Earth and Mars
are part of the inner Solar System, which consists of four rocky planets and the asteroid belt. These terrestrial planets were subjected to a brutal bombardment shortly after their formation, as a torrent of asteroids rained down on the inner Solar System.
While these rocks were assimilated into the crusts of both Earth and Mars, the movement of plate tectonics on our home planet recycled these ancient meteors into the planet’s interior. The surface of Mars, on the other hand, is stationary, which means that rocks that smashed into the planet in the distant past remain in place and can be studied.
The authors of the study
attempted to answer a series of fundamental questions about the origin of 31 Martian meteorites by analyzing them. Scientists, for example, had never determined whether these ancient projectiles originated in the inner or outer Solar System, or whether they carried any organic material that could have allowed life to develop.
Using ultrahigh precision chromium isotope measurements, the researchers identified the meteorites as carbonaceous chondrites from the outer Solar System. The authors calculated that these ancient impacts brought enough water to Mars to cover the entire planet in 307 meters (1,007 feet) of water based on the prevalence of such rocks on Mars and the fact that ice accounts for 10% of their mass.
Carbonaceous chondrites from the outer Solar System
have also been found to transport organic molecules like amino acids to the inner Solar System. These compounds are required for the formation of DNA and are most likely the raw materials that allowed life to emerge.
“At this time, Mars was bombarded with asteroids filled with ice. It happened in the first 100 million years of the planet’s evolution,” explained study author Professor Martin Bizzarro in a statement. “Another interesting angle is that the asteroids also carried organic molecules that are biologically important for life.”
However, while conditions on Mars may have been ideal for life at this early juncture, the same can’t be said for Earth. “After this period, something catastrophic happened for potential life on Earth,” says Bizzaro.
“It is believed that there was a gigantic collision between the Earth and another Mars-sized planet. It was an energetic collision that formed the Earth-Moon system and, at the same time, wiped out all potential life on Earth.”
Taken together, these findings indicate that life had a better chance of thriving on Mars than on Earth during the early years of the inner Solar System.
The study is published in the journal Science Advances.