Why Doesn't Mars Have an Atmosphere Anymore?

Over the past few months scientists have stirred up a huge amount of excitement over findings that suggest there was once life on Mars. Yet for life to exist there has to be an atmosphere, something that Mars is characteristically lacking, at least in its current state. In the past Mars would have been enveloped in an atmosphere which made it possible for the planet to support liquid water sources. Which leaves us with the question – why doesn’t Mars have at atmosphere anymore?

NASA technology begins to unravel the mystery of the missing atmosphere

The answer to the mystery could lie in the hands of NASA’s state-of-the-art Mars Atmosphere and Volatile Evolution (MAVEN) orbiter which has been in Martian orbit since September. Its primary space mission kicked off in mid-November and was launched with the goal of shedding light on why the Red Planet’s atmosphere no longer exists.

Early results reveal new information

While it’s still early days MAVEN has collected results which indicate that solar wind force could have worn down holes in the planet’s lower atmosphere and led to its ultimate depletion.  

An atmospheric breakdown

On most planets the ionosphere deflects solar wind particles. This upper layer of the atmosphere is charged by solar radiation and actively protects the planet. However after Mars’ core cooled and ceased to emit a magnetic field the ionosphere gradually lost its effectiveness against repelling solar wind. MAVEN’s readings supported this theory when its Solar Wind Ion Analyser recorded traces of solar wind particles far lower in the atmosphere than usual.

Bruce Jakosky the project’s principal investigator explains, “We are beginning to see the links in a chain that begins with solar-driven processes acting on gas in the upper atmosphere and leads to atmospheric loss. Over the course of the full mission, we’ll be able to fill in this picture and really understand the processes by which the atmosphere changed over time.”

While the ionosphere is still able to deflect charged particles, neutral particles manage to slip through the net. As they reach the lower regions of the ionosphere they become charged and replicate the destructive effects of solar wind as they force their way out. Developing an understanding of how these neutral particles are able to slip into lower layers of the atmosphere and recharge will help scientists determine whether or not any of the atmosphere’s other layers are affected.

More work to be done…

Scientists may have confirmed that solar wind is largely responsible for the deterioration of the upper atmosphere however they are also looking into whether it affects the lower atmosphere. Using a sophisticated Neutral Gas and Ion Mass Spectrometer MAVEN will continue to investigate the effects of solar wind activity in the lower atmosphere and if  depletion may be causing gas to leak into the ionosphere. So far, MAVEN’s Suprathermal and Thermal Ion Composition (STATIC) tool has recorded ions spilling out of the planet’s atmosphere by breaking through the ionosphere’s protective shield. This creates an ever increasing number of holes which STATIC will use to determine how fast the planet’s atmosphere is deteriorating.