Life In Our Solar System May Have Started On Mars, Not Earth
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https://bit.ly/3Av1ivc)
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 cant 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.
