We know that Mars went through the disappearance of an atmosphere, but how? Presently, Mars is characterized by a sparse atmosphere, with the gases’ volume, being less than 1% of Earth’s.
Surface-based evidence implies that Mars once possessed a denser atmosphere. This would have induced a potent greenhouse effect, capturing solar radiation.
Due to numerous expeditions to Mars, we have gained insights into the planet’s early stages. For example, we have learned that Mars maintained a robust magnetic field until about 4 billion years ago
The magnetic field of Mars was formed through convection currents generated by the planet’s molten core. Just like Earth’s. However, Mars’ core cooled to the extent that this process ceased, resulting in the absence of a global magnetic field.
With the disappearance of an atmosphere, and this magnetic field, Mars lost its primary defence against solar winds. These winds are streams of charged particles emitted by the Sun.
How did the magnetic field collapse on Mars?
The exact cause of the collapse of Mars’ magnetic field, the disappearance of an atmosphere, is a mystery, though there are several hypotheses.
One such hypothesis proposes that Mars originally had three moons, rather than the two we see today (Phobos and Deimos). According to this theory, the third moon would have been significantly larger than the current two, which are relatively small.
This also suggests that the third moon was approximately the size of Io, a moon of Jupiter. The theory also suggests It impacted Mars just before the collapse of the magnetic field.
A second theory is quite similar if a little more plausible. This one suggests that large asteroids colliding with Mars were responsible.
In both theories, the energy released by these impacts would have disrupted the flow of heat in the planet’s core. This would cool the core, shutting off the magnetic field and opening the door for the solar winds. In turn, this would lead to the disappearance of an atmosphere.
How did Earth avoid its own disappearance of an atmosphere?
Nobody is sure how Earth sustains its magnetic field but instead of failing it ‘flips’ every once in a while. This could be a clue as to how it keeps going. Studies have shown that our magnetic field has weakened by as much as 15% in the last 200 years.
While the field is unlikely to fail, it will probably reverse ‘poles’. While this reversal happens, the field will reduce to near zero but it will kick back into gear again.
Solar winds are devastating to planetary atmospheres, but we don’t have anything to worry about just yet.
Solar wind killed the Red Planet
The sun’s Solar Winds, unimpeded by a global magnetic field, began stripping away the majority of the Mars atmosphere – this happened just a few hundred million years after the collapse of the magnetic field.
The process of stripping away the atmosphere happened so quickly (quickly for galactic events, that is) because the Sun rotated a lot faster when it was younger.
A faster rotating, younger Sun, had much more intense solar winds and ultraviolet radiation. Due to this, it was surmised from reports generated by NASA’s MAVEN (Mars Atmosphere and Volatile Evolution Mission) spacecraft that atmospheric losses were much greater during this earlier period.
It was also surmised by the team on the MAVEN project that microbial life could very well have existed on the surface of Mars before these processes intensified (i.e. before the collapse of the global magnetic field).
As the atmosphere on Mars began to be lost to space, any life that was present on the surface may have been forced underground.
Losing the majority of the planet’s atmosphere to space was a major contributor to Mars’ transition from wet and warm, to cold and dry as we know it now. In the end, it was because Earth kept its magnetic field that allowed life to develop and thrive here.
[…] there be life on Mars, ever? Was there life on Mars at any time? Before we tackle any of those, we need a quick biology lesson. More specifically, we […]