Call them Martian fossil hunters.
UNLV research, published recently in the journal Nature Communications, could help assess landing locations and excavation sites for NASA’s 2020 rover mission to Mars that hopes to find evidence of past Martian life in the rocks of the red planet.
The ambitious mission will put a robot on Mars that can extract rock and soil samples to determine if there were living organisms on the planet located some 33.9 million miles away from humans.
NASA’s plan is to grab samples from promising locations and potentially return them to Earth. Locations with clay minerals that indicate where water was once present on Mars are considered good targets, as these environments may have been habitable. Clay minerals are also great at preserving organic molecules on their surfaces and in their interlayers.
There are thousands of locations on Mars believed to have the clay minerals NASA is looking for, including Gale Crater, a 96-mile-wide dry lake bed where the rover Curiosity landed in 2012.
But curiously, the Curiosity mission detected organic molecules in concentrations lower than expected.
That left scientists perplexed, including a team of UNLV geoscientists who set out to explain why the concentration of organics was lower than anticipated.
Researchers, led by UNLV geoscience professor Elizabeth “Libby” Hausrath and former Ph.D. student Seth Gainey, were able to recreate clay minerals in a UNLV geoscience lab akin to what might be found in the Gale Crater. Their work provided an explanation for why the concentrations of organics were lower than anticipated.
It turns out iron-magnesium rich clay minerals may not necessarily be conducive to the preservation of organic matter after all.
“The results suggested that the iron-magnesium rich clay minerals formed quickly under oxidized conditions, which could help explain low concentrations of organics within some rocks or sediments on Mars,” said Gainey.
For decades, experiments suggested that the clay minerals synthesized in this study require anoxic/reducing conditions to form, which is a property beneficial for the preservation of past organic matter, including possible signs of life. The team rigorously tested the assumption that anoxic/reducing conditions were required.
“The fact that organic molecules haven’t been detected in higher concentrations in clay minerals on Mars was puzzling, but the results of our experiments – the fact that we can synthesize clay minerals under conditions that would destroy organic molecules – helps us understand those results,” said Hausrath.
Although the minerals do form under anoxic/reducing conditions, they also form under oxidizing conditions, which would not be ideal for preserving past organic biosignatures. The new results suggest those conditions would actively destroy organic biosignatures, Gainey said.
Fully understanding how the minerals were formed is critical when looking for locations that may preserve organic biosignatures on Mars, which is a crucial aspect of the upcoming Mars 2020 mission.
Grant funding for the research came from the NASA Mars Fundamental Research Program. The research team also included Oliver Tschauner, Christopher Adcock, and Courtney Bartlett of the UNLV Department of Geoscience, and scientists at California Institute of Technology, Stony Brook University, and Argonne National Laboratory.