UCalgary study reveals likely source for a primary greenhouse gas on early Mars

Researchers have taken a significant step closer to understanding the conditions that could have supported life on Mars.

A new study published Feb. 3 in Science Advances, “Observational Constraints on the Process and Products of Martian Serpentinization,” shows that chemical reactions on ancient Mars were capable of generating enough hydrogen to establish a planet-warming greenhouse effect that could’ve allowed for running water.

The study helps explain how evidence of liquid water found through orbiter and rover missions to Mars likely came to be.

Research for the new study began about six years ago when lead author Dr. Benjamin Tutolo, PhD, an associate professor in geoscience at UCalgary, realized that rocks he had sampled near Duluth, Minn. when he was a PhD student at the University of Minnesota were similar in composition to rocks found on Mars — mainly that they were very rich in iron.

The building blocks of life

On Earth, rocks from the mantle go through a process called serpentinization when they come into contact with water. This process generates hydrogen, which, when combined with other gases in the atmosphere, can generate a strong greenhouse effect and thereby help to trap more of the sun’s heat. It’s been speculated that the same process could’ve happened on Mars more than 3.5 billion years ago.

By studying the Duluth samples, Tutolo and his co-author Dr. Nicholas Tosca, PhD, with the University of Cambridge, discovered the serpentinization process in these iron-rich rocks generated around five times more hydrogen, more than enough to help create habitable conditions on ancient Mars.

“Tectonic processes on Earth bring rocks up to the surface — mid-ocean ridges, volcanoes, and so on, have brought these olivine rich rocks up to the surface and whenever they come into contact with water, the reaction goes like gangbusters and that reaction produces hydrogen,” says Tutolo.

“It also produces unique minerals and reduced organic compounds that could then fuel ecosystems and combine with other ingredients to form the building blocks of life.”

NASA connections bear fruit

Tutolo is also a member of NASA’s Mars Science Laboratory Curiosity Rover science team, and Tosca is a member of the Mars2020 Perseverance Rover team. Both missions have found ample evidence of water on Mars, and samples taken by Perseverance in Jezero Crater will eventually be returned to Earth for further study.

“The coolest thing about Curiosity Rover is that is has the ability to analyze minerals with its in situ laboratory. It has shown some evidence of serpentinization already there. We used data from Curiosity, including the chemistry of the olivines that have been analyzed in Gale Crater, in order to understand that,” says Tutolo.

“The science that we’ve done here will help us to interpret the extraordinary discovery by Perseverance that there are olivine-rich igneous rocks there right at the bottom of Jezero Crater — samples of which will eventually be returned to this planet.”

“Nearly every process on Mars has an analog on Earth. But, this particular form of serpentinization that would have occurred on ancient Mars is not normal on Earth. So, understanding those rocks they’ve discovered at the base of Jezero Crater is going to require viewing through the lens of our new results from the Duluth Complex in Minnesota, of all places.”

Once scientists understand how the process for generating hydrogen and stabilizing liquid water on Mars would’ve have worked, they’ll start looking at why both are no longer there.

Next questions are all about geology

“Next, we will have to understand why did the hydrogen go away, why is Mars no longer warm?” says Tutolo. “You need this backdrop to understand the rocks that are there. What are the time scales? What are the chemical processes that were happening in the rocks that records this transition?”

Ultimately, Tutolo believes a better understanding of the geological processes on Mars can lead to a better understanding of Earth, including forces of climate change we are currently experiencing.

“The value of studying Mars is that it doesn’t have plate tectonics, all the rocks that are there have been there for 3.5 billion years at least. We have snippets of Earth that exist from that time, but the entirety of Mars exists from that time,” says Tutolo.

“So, we can study things like, if the sun was cooler back then how did that affect the planetary surface? Why did biological evolution take so long to take off? Why did it take organisms so long to populate the continents? and so on. All this we can begin to understand by looking at the history of our solar system as recorded on Mars.”