Purdue University
The accepted view of Mars is red rocks and craters as far as the eye can see. That’s what scientists expected when they landed the Perseverance rover in Jezero Crater, a spot chosen in part for the crater’s history as a lake and 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: Instead of the expected sedimentary rocks — washed down by rivers and deposited on the lake floor — many of the rocks are volcanic in nature. Specifically, they consist of large grains of olivine, the muddier version of the gemstone-like peridot that paints so many of Hawaii’s 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, in Purdue’s College of Science, were instrumental in the discovery and analysis of this data, recently published in a series of papers in the journals Science and Science Advances. Wiens led the design and construction of Perseverance’s SuperCam, which helps analyze rock samples and determine their type and origin. Horgan helped select Jezero Crater as the rover’s landing site and is now using the Mastcam-Z cameras on Perseverance to put his discoveries into geological context. “We started to realize that these layered igneous rocks that we were seeing looked different than the igneous rocks that we have these days on Earth,” Wiens said. “They are very similar to igneous rocks on Earth from the beginning of its existence.” The rocks and lava the rover examines on Mars are nearly 4 billion years old. Old rocks exist on Earth, but they are incredibly weathered and battered, thanks to Earth’s active tectonic plates as well as the weathering of billions of years of wind, water, and life. On Mars, these rocks are pristine and much easier to analyze and study. Understanding the rocks on Mars, their evolution and history, and what they reveal about the history of planetary conditions on Mars helps researchers understand how life might have arisen on Mars and how it compares to early life and conditions on ancient Earth . “One of the reasons we don’t really understand where and when life first appeared on Earth is because these rocks are mostly gone, so it’s really hard to reconstruct what ancient environments were like on Earth,” Horgan said. “The rocks that Perseverance is wandering around in Jezero have pretty much just been sitting on the surface for billions of years, waiting for us to come and see them. This is one of the reasons Mars is an important laboratory for understanding the early solar system.” Scientists can use the conditions on early Mars to help extrapolate the environment and conditions on Earth at the same time that life was beginning to form. 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 lead to a deeper understanding of biological processes here on Earth. The search for life is one of Perseverance’s main 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 aged lava flows of Jezero Crater raises hopes for what lies in the sedimentary rocks the mission is now examining. “We are excited to see even better results on organic and ancient habitable environments,” said Horgan. “I think it really sets the scene that Mars is this watery, habitable place, and all the samples we get will help us understand the history of ancient microbial life on Mars.” The equipment and innovative instruments help the rover carry out its mission in a way no other rover has yet, emphasizing the need to land on the planet so scientists can examine and understand what’s really going on. “From orbit, we looked at these rocks and said, ‘Oh, they have beautiful layers!’ So we thought they were sedimentary rocks,” Horgan said. “And it wasn’t until we got really close and looked at them, at the millimeter scale, that we realized these are not sedimentary rocks. It is actually ancient lava. It was a huge moment when we got it on the ground, and it really demonstrated why we need this kind of exploration. The tools we have on the rover are vital because it was impossible to understand the origin of these rocks until we got up close and used all our amazing microscopic instruments to see them.” The search for life is one of Perseverance’s main 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 aged lava flows of Jezero Crater raises hopes for what lies in the sedimentary rocks the mission is now examining. “We’re excited to see even better results on organic and ancient habitable environments,” Horgan said. “I think it really sets the scene that Mars is this watery, habitable place, and all the samples we get will help us understand the history of ancient microbial life on Mars.” The equipment and innovative instruments help the rover carry out its mission in a way no other rover has yet, emphasizing the need to land on the planet so scientists can examine and understand what’s really going on. “From orbit, we looked at these rocks and said, ‘Oh, they have beautiful layers!’ So we thought they were sedimentary rocks,” Horgan said. “And it wasn’t until we got really close and looked at them, at the millimeter scale, that we realized these are not sedimentary rocks. It is actually ancient lava. It was a huge moment when we got it on the ground, and it really demonstrated why we need this kind of exploration. The tools we have on the rover are vital because it was impossible to understand the origin of these rocks until we got up close and used all our amazing microscopic instruments to see them.” Igneous soil with stratified composition and density in Jezero Crater, Mars, Science Advances Astrobiology
