Mars was the place to be way back when the rock was young.
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Was there life on Mars? Image: joshimerbin/Shutterstock.com |
The organic molecules that enabled life to emerge were
present on Mars around 4.5 billion years ago, new research suggests. 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.
Earth and Mars are both members of inner Solar System, which
is made up of four rocky planets and the asteroid belt. Shortly after their
formation, these terrestrial planets endured a brutal bombardment as a torrent
of asteroids rained down on the inner Solar System.
While these rocks became assimilated into the crust of both
Earth and Mars, the movement of plate tectonics on our home world caused these
ancient meteors to be recycled into the interior of the planet. In contrast,
the surface of Mars is stationary, which means the rocks that smashed into the
planet in the distant past remain in place and can be studied.
By analyzing 31 Martian meteorites, the study authors sought
to answer a series of fundamental questions about their origin. For example,
until now scientists had never determined whether these ancient projectiles
came from the inner or outer Solar System, or whether they carried any of the
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. Based on the prevalence of such rocks on Mars and the fact that
ice usually accounts for 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 (1,007 feet) of water.
Significantly, carbonaceous chondrites from the outer Solar
System are also known to have transported organic molecules such as amino acids
to the inner Solar System. These compounds are essential for the formation of
DNA, and are likely to have provided 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 suggest that life probably
had a better chance of thriving on Mars than on Earth during the formative
years of the inner Solar System.
The study is published in the journal Science Advances.
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