Mars used to be wetter and warmer back in the past, and maybe a good candidate for life the way we know it. The scientific explanation is that it lost its atmosphere because of solar wind.
In 2013, NASA launched a robotic probe, called MAVEN or Mars Atmosphere and Volatile Evolution, in an attempt to address this mystery of the red planet. The spacecraft arrived in the planet's orbit in 2014 and it has since made more than 4,000 elliptical orbits, analyzing the Martian upper atmosphere.
Mars' Lost Atmosphere, No Longer A Mystery
A few years after the MAVEN's launch, the team in charge of the probe published its major finding and suggested that most of the planet's atmosphere was, in fact, scraped from Mars by solar wind.
Solar wind is a stream of electrons and protons that the sun emits. While our planet is shielded by a magnetic field and manages to escape the solar wind's effects, the red planet is not as lucky.
These findings are consistent with previous research which suggested that Mars used to have Earth-like characteristics back in the day. However, until this paper, scientists haven't managed to hypothesize the process through which Mars had lost its capacity to support life.
The results of this scientific observation were published, March 31, in the journal Science.
Earth Loses 90 Tons Of Atmosphere Daily
Mars isn't the only planet losing its atmosphere, Earth also suffers from the similar problem.
Our magnetic field protects us from solar wind, defending and rerouting the wind — similar to the way a rock would obstruct a water stream. In our case, the reason for atmospheric leakage is not the same as the red planet's, so scientists had to find a different explanation.
However powerful our magnetic field is, it is not indestructible and also has its flaws — making Earth face atmospheric problems. At its poles, the field lines are open, similar to a standard bar magnet. This is a perfect spot for the particles of solar wind to head inside our planet. As solar wind particles can get in, our atmosphere can get out through these shield cracks.
The entire process through which this happens continues to be a mystery. Although Cluster and other similar missions have unveiled important parts of this atmospheric black box, there is still much to be found out.
Every day, Earth loses around 90 tons of material from its upper atmosphere. The material streams directly out into space. There have been a number of missions trying to understand the core of this problem, among which is ESA's Cluster feet, who have extensively investigated this leakage.
As the expanse of our planet's atmosphere is quite abundant, 90 tons a day represents a small leak, which makes it far from a worrying problem.
The Bigger Question: Finding Habitable Planets
The researchers want to understand the underlying mechanism how the atmosphere gets lost, which could help them extrapolate it to other planets as well. In our attempt to find habitable planets, understanding the reasons why many of them (including ours) keep losing their atmosphere is crucial.