Though Mars is believed to once have had a thick atmosphere capable of keeping the planet warm enough to sustain liquid water, it is now a thin, wispy remnant of its former self. NASA launched the Mars Atmosphere And Volatile EvolutioN (MAVEN) orbiter nearly two years ago in order to find out what happened to the atmosphere of the red planet.
MAVEN has now returned data that details how solar wind effectively stripped Mars of its atmosphere, which changed the landscape of the planet in incredible ways.
The Sun is constantly blasting out radiation, which is fairly harsh. Earth is protected by much of these effects because of the magnetic field. (Fun fact: radiation interacting with the magnetic field is how aurorae form.) Mars doesn't have much in the way of a magnetic field, so its protection is limited. As a result, solar wind has been able to wear down a catastrophic amount of the atmosphere at a rate of 100 grams per second. Over the course of a few billion years, the planet's atmosphere was stripped away almost entirely.
"Solar-wind erosion is an important mechanism for atmospheric loss, and was important enough to account for significant change in the Martian climate," explained NASA's Joe Grebowsky. "MAVEN also is studying other loss processes — such as loss due to impact of ions or escape of hydrogen atoms — and these will only increase the importance of atmospheric escape."
But why is this important?
Learning what became of the atmosphere is crucial to knowing what happened to all of the planet's water. It is thought that Mars was once covered with extensive oceans. While NASA announced in September that briny liquid water still exists on the fourth planet, it is in greatly reduced quantities.
"Understanding what happened to the Mars atmosphere will inform our knowledge of the dynamics and evolution of any planetary atmosphere," NASA's John Grunsfeld announced in a statement. "Learning what can cause changes to a planet's environment from one that could host microbes at the surface to one that doesn't is important to know, and is a key question that is being addressed in NASA's journey to Mars."
Liquid water is essential for the existence of life as we know it, and figuring out how the Martian atmosphere was stripped away is a key piece of the puzzle.
(Header image: NASA / Goddard Space Flight Center)