Today’ Mars is very cold, very dry and very inhospitable, practically a dead place but this wasn’t always the case, things were very different in the ancient past. Scientists believe early Mars had a substantial atmosphere in the past than it does today, an atmosphere much more similar to Earth’s.
More than 3.6 billion years ago, climatic conditions appear to have been favorable for the presence of liquid water on Mars’ surface, this in turn gave rise to speculation that Mars was capable of supporting life and even a home to a native civilization.
But over time, the Red Planet lost most of its carbon dioxide-dominated atmosphere; this atmospheric loss led to depressurization and cooling, and is thought to be the primary driving force responsible for the loss of liquid water from its surface.
We think that all of the action took place between about 4.2 to 3.7 billion years ago,
MAVEN principal investigator Bruce Jakosky, said.
The present atmospheric surface pressure is about 6 millibars on an average, which is about 0.6% of Earth’s, and is composed of 95.32% CO
One of the main differences between the Earth and Mars is the lack of a significant magnetic field and smaller surface gravity on Mars. A global magnetic field provides shielding from incoming charged particles and also prevents escape of outgoing ions.
Mars is too small, has only half Earth’s diameter, 11% its mass and 38% its gravity thus making it easy for upper layers to escape into the vacuum of space.
All of these [factors] point to the loss of the Martian atmosphere in the earliest stages,
Jakosky said. In 2015, Jakosky and his colleagues suggest that the solar wind was a major driver of Martian atmosphere loss:
That stripping would then have proceeded very quickly, “within a few hundred million years after the shutoff of the magnetic field,
Our observations show unambiguously that a planet with no global magnetic field can [be] exposed to the full force of the solar wind and solar storms,
Mars’ atmosphere took a beating.
Nearby Supernovae contribute to Mars atmosphere loss?
In a new study, uploaded on arxiv servers on May 3, astronomer Dimitra Atri suggest that in addition to solar storms and radiations, it is likely that Mars atmosphere has been exposed to radiation bursts from high-energy astrophysical sources which become highly probable on timescales of billion years and beyond.
The idea that nearby supernovae can inject energy and damage planetary atmospheres was given by Ruderman (1974). Recent reports based on the on measurements of 60Fe deposition on the ocean floor provide evidence of a 2.2 million years old supernova located at a distance between 20-430 light years away from Mars.
So, supernovae explosion are not rare, scientists calculated this frequency of such nearby explosions, with at least one event occurring every 2-4 million year. On timescales of billion of years, such events become important.
On longer timescales of billion years, one can assume that a large number of such events would have deposited energy in the Martian atmosphere.
Atri team’ calculations suggest a significant probability of a Galactic GRB beaming towards the Red Planet in the past 1 billion years. Atri’ models appears to be the most effective in Mars atmosphere depletion due to long duration of the event.
It’s incredibly satisfying to get to this point and realize that we really are answering the questions we set out to when we started the mission,
We’re beginning to understand what drives climate change on Mars, and to try to generalize to planets more generally.