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| This artist’s impression shows how Mars may have looked about four billion years ago. |
Today, Mars is colloquially known as the 'Red Planet' on account of how its
dry, dusty landscape is rich in iron oxide (aka. 'rust'). In addition, the
atmosphere is extremely thin and cold, and no water can exist on the surface
in any form other than ice.
But as the Martian landscape and other lines of evidence attest, Mars was
once a very different place, with a warmer, denser atmosphere and flowing
water on its surface.
For years, scientists have attempted to determine how long natural bodies
existed on Mars and whether or not they were intermittent or persistent.
Another important question is how much water Mars once had and whether or
not this was enough to support life. According to a
new study
by an international team of planetary scientists, Mars may have had enough
water 4.5 billion years ago to cover it in a global ocean up to 300 meters
(almost 1,000 feet) deep.
Along with organic molecules and other elements distributed throughout the
Solar System by asteroids and comets at this time, they argue, these
conditions indicate that Mars may have been the first planet in the Solar
System to support life.
The paper that describes their research and findings recently
appeared in Science Advances. As they indicate in their paper, the terrestrial planets endured a period
of significant asteroid impacts (the Late Heavy Bombardment) following their
formation over 4.5 billion years ago.
These impacts are believed to be how water and the building blocks for life
(organic molecules) were distributed throughout the Solar System. However,
the role of this period in the evolution of rocky planets in the inner Solar
System – particularly where the distribution of volatile elements like water
is concerned – is still debated.
For the sake of their study, the international team reported on the
variability of a single chromium isotope (54Cr) in Martian meteorites dated
to this early period. These meteorites were part of Mars' crust at the time
and were ejected due to asteroid impacts that sent them off into space.
In other words, the composition of these meteorites represents Mars'
original crust before asteroids deposited water and various elements on the
surface.
Since Mars does not have active plate tectonics like Earth, the surface is
not subject to constant convection and recycling. Therefore, meteorites
ejected from Mars billions of years ago offer a unique insight into what
Mars was like shortly after the planets of the solar system formed.
As co-author Professor Bizzarro from the StarPlan Center said in a UCPH
faculty press release:
"Plate tectonics on Earth erased all evidence of what happened in the first
500 million years of our planet's history. The plates constantly move and
are recycled back and destroyed into the interior of our planet. In
contrast, Mars does not have plate tectonics such that planet's surface
preserves a record of the earliest history of the planet."
By measuring the variability of 54Cr in these meteorites, the team estimated
the impact rate for Mars circa 4.5 billion years ago and how much water they
delivered.
According to their results, there would have been enough water to cover the
entire planet in an ocean at least 300 meters in depth (~1,000 feet) and up
to 1 kilometer (0.62 miles) deep in some areas.
In comparison, there was very little water on Earth at this time because a
Mars-sized object had collided with Earth, leading to the formation of the
Moon (i.e., the Grand Impact Hypothesis).
In addition to water, asteroids also distributed organic molecules like
amino acids (the building blocks of DNA, RNA, and protein cells) to Mars
during the Late Heavy Bombardment. As Bizarro explained, this means that
life could have existed on Mars when Earth was sterile:
"This happened within Mars's first 100 million years. After this period,
something catastrophic happened for potential life on Earth. 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."
This study is similar to recent research that used the deuterium-to-hydrogen
ratios of Martian meteorites to create models of atmospheric evolution.
Their findings showed that Mars may have been covered in oceans when Earth
was still a molten ball of rock.
These and other questions related to Mars' geological and environmental
evolution will be investigated further by robotic missions destined for Mars
in this decade (followed by crewed missions in the 2030s).
This article was originally published by Universe Today. Read the
original article.
Tags:
Space & Astrophysics