The sands of Mars are both green and red, according to the Perseverance rover

Geological findings hint at the conditions under which life originated on Earth – and possibly on Mars

WEST LAFAYETTE, Ind. – The accepted view of Mars is red rocks and craters as far as the eye can see. That’s pretty much what scientists expected when they landed the Perseverance rover in Jezero Crater, a location chosen in part for the crater’s history as a lake and as part of a rich river system, when Mars had liquid water, air and a magnetic field.

What the rover found once on the ground was surprising: rather than the expected sedimentary rocks – washed down by rivers and accumulated at the bottom of the lake – many rocks are volcanic in nature. Specifically, they’re made up of large grains of olivine, the muddier, less gem-like version of peridot that dyes so many Hawaiian beaches dark green.

Planetary scientists Roger Wiens, professor of earth, atmospheric and planetary sciences, and Briony Horgan, associate professor of earth, atmospheric and planetary sciences at Purdue’s College of Science, played a role instrumental in the discovery and analysis of these data, recently published in a series of articles in the journals Science and Science Advances.

Briony Horgan, associate professor of planetary sciences at Purdue University, inside the Mars Rover Operations Center at Purdue’s Delon and Elizabeth Hampton Hall of Civil Engineering. Horgan helped select Jezero Crater as the landing site for Perseverance. His geological expertise helps put the rover’s discoveries into context. (Credit: Purdue University Photo/Rebecca McElhoe) Download Image

Wiens led the design and construction of Perseverance’s SuperCam, which allows rock samples to be analyzed and their type and origin to be determined. Horgan helped select Jezero Crater as the rover’s landing site and now uses the Mastcam-Z cameras on Perseverance to put his findings into geological context.

“We started to realize that these layered igneous rocks that we were seeing were different from the igneous rocks that we have on Earth today,” Wiens said. “They look a lot like igneous rocks on Earth at the start of its existence.”

The rocks and lava the rover is examining on Mars are nearly 4 billion years old. Ancient rocks exist on Earth but are incredibly weathered and battered, thanks to the Earth’s active tectonic plates as well as the weathering effects of billions of years of wind, water, and life. On Mars, these rocks are pristine and much easier to analyze and study.

Understanding rocks on Mars, their evolution and history, and what they reveal about the history of planetary conditions on Mars helps researchers understand how life may have appeared on Mars and how that compares to life and to early conditions on ancient Earth.

Roger Wiens, associate professor of planetary science at Purdue University and Mars rover expert at Purdue University with a topographic model of Mars and a photo of the Curiosity rover. He is the principal investigator of the SuperCam team at Perseverance and the ChemCam team at Curiosity. (Credit: Purdue University Photo/John Underwood) Download Image

“One of the reasons we don’t fully understand where and when life first evolved on Earth is that these rocks have mostly disappeared, so it’s very difficult to reconstruct what ancient environments were like. on Earth,” Horgan said. “The rocks that Perseverance walks on in Jezero have more or less sat on the surface for billions of years, waiting for us to come and look at them. This is one of the reasons why Mars is an important laboratory for understanding the early solar system.

Scientists can use conditions in early Mars to help extrapolate the environment and conditions on Earth at the same time life was beginning to appear. Understanding how and under what conditions life began will help scientists know where to look for it on other planets and moons, as well as better understand biological processes here on Earth.

The search for life is one of Perseverance’s primary goals and one of the reasons it landed in Jezero Crater in the first place. Discovering the potential for habitable environments in something as uninhabitable as the ancient lava flows of Jezero Crater brings hope for what lies in the sedimentary rocks the mission is currently examining.

“We’re excited to see even better results on organics and former habitable environments,” Horgan said. “I think it really sets the stage that Mars is this aquatic, habitable place, and all of the samples that we collect are going to help us understand the history of ancient microbial life on Mars.”

The innovative equipment and instruments help the rover carry out its mission like no other rover has done before, highlighting the need to land on the planet so scientists can examine and understand what is really going on.

“From orbit, we looked at these rocks and thought, ‘Oh, they have nice layers!’ So we thought it was sedimentary rock,” Horgan said. “And it wasn’t until we looked at them very closely, on a millimeter scale, that we understood that they weren’t sedimentary rocks. They are actually ancient lava. It was a huge moment when we realized this in the field, and it really illustrated why we need this kind of exploration. The tools we have on the rover are vital because it was impossible to figure out where these rocks came from until we got up close and used all of our amazing microscopic instruments to look at them.

More than 40 co-authors have been listed in the suite of papers from national and international facilities, including NASA’s Jet Propulsion Lab and Los Alamos National Laboratory.

Horgan, Wiens and their Purdue collaborators will continue to analyze and guide Perseverance’s discoveries and ideas about the history of Mars, just as Purdue scientists continue to help analyze rocks from the Apollo lunar missions that put both the first and the last human on the moon.

About Purdue University

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Media contacts: Brian Huchel, [email protected],
Brittany Steff, [email protected]

Sources: Briony Horgan [email protected]

Roger Wiens [email protected]


Igneous terrain stratified in composition and density in Jezero Crater, Mars.
Scientists progress
The abstract and list of authors are available online.

Water-weathered igneous rocks sampled from the floor of Jezero Crater, Mars
The abstract and list of authors are available online.

A cumulated olivine outcrop on the floor of Jezero Crater, Mars
The abstract and list of authors are available online.