A new study published in the journal Science Advances suggests that the organic molecules that allowed life to begin were present on Mars about 4.5 billion years ago.
And while these critical components may have hit Earth around the same time, it was on the Red Planet that life found its most favorable conditions.
Earth and Mars are members of the inner solar system, made up of four rocky planets and an asteroid belt. Shortly after their formation, these terrestrial planets were brutally bombarded when a shower of asteroids hit the inner solar system.
While these rocks were assimilated into the crust of Earth and Mars, the movement of plate tectonics on our home world caused these ancient meteors to fall into the interior of the planet.
In contrast, the surface of Mars is stationary, meaning that rocks that crashed into the planet in the distant past remain in place and can be studied.
By analyzing 31 Martian meteorites, the authors of the study sought to answer a number of fundamental questions about their origin.
For example, until now, scientists have not determined where these ancient projectiles from the inner or outer solar system came from, and whether they carried any organic material that could allow life to develop.
Using ultra-precise measurements of chromium isotopes, the researchers identified the meteorites as carbonaceous chondrites from the outer solar system.
Based on the prevalence of such rocks on Mars and the fact that ice typically makes up 10 percent of their mass, the authors calculated that these ancient impacts brought enough water to Mars to cover the entire planet in 307 meters of water.
Remarkably, carbonaceous chondrites from the outer solar system also transported organic molecules such as amino acids to the inner solar system.
These compounds are essential for the formation of DNA and likely provided the raw materials that allowed life to begin.
“At this time, Mars was bombarded with ice-filled asteroids. This happened in the first 100 million years of the evolution of the planet ,” study author Professor Martin Bizzarro explained in a statement. “Another interesting aspect is that the asteroids also carried organic molecules that are biologically important to life.”
However, while conditions on Mars may have been ideal for life at this early stage, the same cannot be said for Earth. “After that period, something catastrophic happened to potential life on Earth, ” says Bizzaro.
It is believed that a giant collision has taken place between Earth and another planet the size of Mars. It was an energetic collision that formed the Earth-Moon system and at the same time destroyed all potential life on Earth.
Taken together, these results indicate that life likely had a better chance of thriving on Mars than on Earth during the formative years of the inner solar system.