About 3.8 billion years ago, Mars had a moderately dense atmosphere, and its surface pressure was equal to or slightly less than that on Earth. However, the red planet has a very thin atmosphere today. Now a group of researchers at California Institute of Technology (Caltech) and NASA’s Jet Propulsion Laboratory have concluded that ultraviolet rays from Sun stripped the Martian atmosphere of carbon dioxide. It solves the long-standing mystery of the “missing” carbon on Mars.
Mars is still losing tons of atmosphere every day
Findings of the study were published Tuesday in the journal Nature Communications. Caltech postdoctoral fellow Renyu Hu, the lead author of the study, said transition of the dense Martian atmosphere into a thin one was entirely possible. Scientists found that the strong solar wind is still stripping away tons of Martian atmosphere every day. There are two ways for the removal of carbon dioxide from the atmosphere. It was either lost to space or was incorporated into minerals in rocks, known as carbonates.
Scientists were surprised when they found that the extra carbon was not captured into Martian rocks. The new study not only explains the loss of carbon over the last 3.8 billion years, but also why today’s atmosphere has more carbon-13 than carbon-12. NASA’s MAVEN mission has found evidence that more than 100 grams of particles are stripped from today’s Martian atmosphere every second via a process called sputtering. This process involves interactions between solar wind and the red planet’s upper atmosphere.
Carbon-12 more likely to escape than carbon-13
The modern day Martian atmosphere is far more enriched in carbon-13, compared to carbon-12, than it should be as a result of sputtering alone. Hu and his colleagues identified a mechanism that could have helped in the carbon-13 enrichment. It begins when UV rays from the Sun strike a carbon dioxide molecule in the upper atmosphere, splitting it into carbon monoxide and oxygen.
Next, the UV light strikes the carbon monoxide to split it into carbon and oxygen. Some of these carbon atoms have sufficient energy to escape from the atmosphere. Scientists found that carbon-12 was much more likely to escape than carbon-13. It solves the long-standing paradox of missing carbon.
