Atmosphere Discoveries Provide Insight to Life on Mars

While NASA robots have been digging and drilling to collect rock on Mars, a team of UCSD scientists say the real action is in the air. Dust may contain the secrets to life on Mars and other planets.

Researchers have discovered chemical reactions that occur on the surface of carbonate particles in the atmosphere. These particles could give us insight into how life begins on a planet.

One basic requirement of life is large organic molecules. For these to form naturally, scientists thought two important conditions were necessary: lots of water and lots of time. Water so that chemicals like ammonia and methane can float around, and time so that they can bump into each other and create chemical reactions that are the first signs of life. But Robina Shaheen, a postdoctoral associate that worked on the project, said her research shows that all you might need is a little water and some mineral dust.

The research’s principle investigator and biochemistry professor Mark Thiemen said the thin layer of water surrounding dust particles creates a previously unknown environment, where chemical reactions can occur very quickly. The new environment created by the interaction of dust particles and water means that the chemicals that need to bump into each other are going faster, and are more likely to collide and form organic molecules.

Shaheen said the reaction can go so quickly that carbonate, a type of mineral that usually takes days to weeks to form, could form in as little as seconds.

Since the discovery of carbonate in Martian meteorites, many scientists took it a sign of life on Mars. Here on Earth, calcium carbonate is produced by creatures in the ocean as shells and later deposited as sedimentary rock.
Animals like snails and tiny plankton can make carbonate very quickly because they use complex biochemistry.

Shaheen showed that fast formation of carbonate doesn’t need biochemistry. It can occur on the surface of dust grains in the atmosphere.

“The whole trick is rate,” Theimen said. “You have to goose the rate. For hundreds of years, we’ve understood how reactions occur in water [but] all these rules go away when you’re on the surface of a particle.”

Shaheen said the team began by studying how aerosol pollutants move from one place to another. But once her team analyzed some samples they saw new chemistry they didn’t expect. Carbonate was being formed on the particles. The problem was no one knew what was happening in the air.

The team used oxygen isotope 17 to track the formation of carbonate in the particles. When they compared that with the formation of carbonate in a Martian meteorite, Thiemen said they found strong similarities.

The findings have implications closer to home. Shaheen said that by understanding the composition of aerosols in our own environment we come closer to figuring out patterns of rain and snowfall.

“It’s important for the Earth overall from a climate change perspective,” Shaheen said.

Pollutant could absorb more solar radiation depending on the reactions that occur on their surface, Shaheen explained. If they got into snow it could cause snow pack to melt faster, disrupting access to water for many people. She hopes that using this new technique to analyze aerosols will help others determine how pollution is directly impacting hydrologic cycles.