The Mars rover found that the floor of the Jezero crater is composed of volcanic rocks that have interacted with water.
NASA scientists were in for a big surprise when the Perseverance Mars rover began analyzing rocks on the floor of Jezero Crater in the spring of 2021: They expected to find sedimentary rocks because the crater held a lake billions of years ago. This would have formed when sand and mud settled in a once watery environment. Instead, they discovered that the floor was made of two types of igneous rock – one formed by volcanic activity on the surface and the other derived from magma deep underground. The findings are described in four new Science papers published today, August 25, 2022. In Science, one offers an overview of Perseverance’s exploration of the crater floor before reaching the ancient Jezero River delta in April 2022. A second study in the same journal details the distinctive rocks that appear to have formed from a thick body of magma. The other two papers, published in Science Advances, document the unique ways Perseverance’s rock evaporation laser and ground-penetrating radar found that igneous rocks cover the crater floor.
Rock of Ages
Igneous rocks make excellent timers. This is because the crystals inside record details about the exact moment they formed. “A great value of the igneous rocks we collected is that they will tell us about when the lake was present at Jezero. We know they were there more recently than the igneous rocks of the crater floor formed,” said Ken Farley of Caltech, a Perseverance project scientist and lead author of the first of the new Science papers. “This will answer some important questions: When was the Martian climate favorable for lakes and rivers on the planet’s surface, and when did it change to the very cold and dry conditions we see today?” Perseverance captured this close-up of a rocky target nicknamed “Foux” using the WATSON camera on July 11, 2021, the 139th Martian day, r sol, of the mission. The area inside the camera is approximately 1.4 by 1 inch (3.5 cm by 2.6 cm). Credit: NASA/JPL-Caltech/MSSS However, igneous rock is not ideal for preserving the potential signs of ancient microscopic life that persistence is looking for, because of how it is formed. On the other hand, determining the age of sedimentary rock can be difficult, especially when it contains rock fragments that formed at different times before the sediment was deposited. However, sedimentary rocks often form in aquatic environments suitable for life and are better at preserving ancient signs of life. That’s why the sediment-rich delta of the Perseverance River it’s been exploring since April 2022 is so enticing to scientists. The rover has begun drilling and collecting core samples of sedimentary rocks there so that the Mars Sample Return campaign could potentially return them to Earth, where they could be studied by powerful laboratory equipment too large to carry to Mars.
Mysterious rocks formed by magma
A long-standing mystery on Mars is solved in a second paper published in Science. Mars orbiters spotted a rock formation filled with the mineral olivine years ago. Covering an area of about 27,000 square miles (70,000 square kilometers)—almost the size of South Carolina—this formation extends from the inner rim of Jezero Crater into the surrounding area. Scientists have offered several theories about why olivine is so abundant over such a large area of the surface. These include meteorite impacts, volcanic eruptions and sedimentary processes. Another theory is that olivine formed deep underground from slowly cooling magma – molten rock – before being exposed over time by erosion. NASA’s Perseverance Mars rover looks over an expanse of boulders on the floor of Jezero Crater in front of a site nicknamed “Santa Cruz” on February 16, 2022, the 353rd Martian day or day of the mission. Credit: NASA/JPL-Caltech/MSSS Yang Liu of NASA’s Jet Propulsion Laboratory (JPL) in Southern California and her co-authors have determined that the latter explanation is the most likely. Persistence rubbed a rock to reveal its composition. Scientists studying the exposed patch identified the large grain size of the olivine, along with the chemistry and texture of the rock. Using Perseverance’s Planetary Instrument for X-ray Lithochemistry, or PIXL, they determined the olivine grains to be in the 1- to 3-millimeter size range — much larger than expected for olivine formed in rapidly cooling lava on the planet’s surface. “This large crystal size and its uniform composition in a particular rock texture require a very slow cooling environment,” Liu said. “So, most likely, that magma in Jezero was not coming to the surface.”
Unique Science Tools
The findings of the scientific instruments that helped establish that igneous rocks cover the crater floor are detailed in the two Science Advances papers. The instruments include Perseverance’s SuperCam laser and a ground-penetrating radar called RIMFAX (Radar Imager for Mars’ Subsurface Experiment). The SuperCam is equipped with a rock vaporizing laser that can hit a target as small as a pencil tip from up to 20 feet (7 meters) away. It analyzes the resulting vapors using a visible light spectrometer to determine the chemical composition of a rock. During Perseverance’s first 10 months on Mars, SuperCam scored 1,450 points, helping scientists reach their conclusion about the igneous rocks on the crater floor. Image of the Mars Perseverance Rover using its SuperCam instrument to hit a rock with a laser to test what it’s made of. Credit: NASA In addition, SuperCam used near-infrared light—it’s the first instrument on Mars with this capability—to find these water-altered minerals in the rocks of the crater floor. However, the changes were not widespread across the crater floor, according to the combination of laser and infrared observations. “The SuperCam data suggest that either these rock layers were isolated from the water of Lake Jezero or that the lake existed for a limited duration,” said Roger Wiens, SuperCam principal investigator at Purdue University and Los Alamos National Laboratory. RIMFAX marks another first. Although Mars orbiters carry ground-penetrating radars, no spacecraft on the Martian surface have before Persistence. Being on the surface, RIMFAX can provide unparalleled detail and has explored the crater floor up to 50 feet (15 meters) deep. Its high-resolution “radargrams” show layers of rock unexpectedly tilted as much as 15 degrees below the ground. Understanding the sequence of these rock layers can help scientists create a timeline of the formation of Jezero Crater. “As the first such instrument to operate on the surface of Mars, RIMFAX has demonstrated the potential value of a ground-penetrating radar as a tool for subsurface exploration,” said Svein-Erik Hamran, RIMFAX principal investigator at the University of Oslo in Norway. . The science team is excited about what they’ve found so far, but they’re even more excited about the science ahead. Bibliographical references: “Compositionally and density stratified igneous terrain in Jezero crater, Mars” by Roger C. Wiens, Arya Udry, Olivier Beyssac, Cathy Quantin-Nataf, Nicolas Mangold, Agnès Cousin, Lucia Mandon, Tanja Bosak, Olivier McLennan, Scott M. Violaine Sautter , Adrian Brown, Karim Benzerara, Jeffrey R. Johnson, Lisa Mayhew, Sylvestre Maurice, Ryan B. Anderson, Samuel M. Clegg, Larry Crumpler, Travis SJ Gabriel, Patrick Gasda, James Hall, Briony HN Horgan, Linda Kah, Carey Legett , Juan Manuel Madariaga, Pierre-Yves Meslin, Ann M. Ollila, Francois Poulet, Clement Royer, Shiv K. Sharma, Sandra Siljeström, Justin I. Simon, Tayro E. Acosta-Maeda, Cesar Alvarez-Llamas, S. Michael Angel , Gorka Arana, Pierre Beck, Sylvain Bernard, Tanguy Bertrand, Bruno Bousquet, Kepa Castro, Baptiste Chide, Elise Clavé, Ed Cloutis, Stephanie Connell, Erwin Dehouck, Gilles Dromart, Woodward Fischer, Thierry Fouchet, Raymond Francisg, , Olivier Gasnault, Erin Gibbons, Sanjeev Gupta, Elisabeth M. Hausr ath, Xavier Jacob, Hemani Kalucha, Evan Kelly, Elise Knutsen, Nina Lanza, Javier Laserna, Jeremie Lasue, Stéphane Le Mouélic, Richard Leveille, Guillermo Lopez Reyes, Ralph Lorenz, Jose Antonio Manrique, Jesus Martinez-Frias-Frias-Crionedine, T Melikechi, David Mimoun , Franck Montmessin, Javier Moros, Naomi Murdoch, Paolo Pilleri, Cedric Pilorget, Patrick Pinet, William Rapin, Fernando Rull, Susanne Schröder, David L. Shuster, Rebecca J. Smith, Alexander E. Stott, Jesse Tarnas, Nathalie Turenne, Marco Veneranda, David S. Vogt, Benjamin P. Weiss, Peter Willis, Kathryn M. Stack, Kenneth H. Williford, Kenneth A. Farley and The SuperCam Team, 25 August 2022, Science Advances.DOI: 10.1126/sciadv .abo3399 “An olivine cumulate outcrop on the floor of Jezero crater, Mars” by Y. Liu, MM Tice, ME Schmidt, AH Treiman, TV Kizovski, JA Hurowitz, AC Allwood, J. Henneke, DAK Pedersen, SJ VanBommel, MWM Jones, AL Knight, BJ Orenstein, BC Clark, WT Elam, CM Heirwegh, T. Barber, LW Beegle, K. Benzerara, S. Bernard, O. Beyssac, T. Bosak, AJ Brown, EL Cardarelli, DC Catling, JR Christian, EA Cloutis, BA Cohen, S. Davidoff, AG Fairén, KA Farley, DT Flannery, A. Galvin, JP Grotzinger, S. Gupta, J. Hall, CDK Herd, K. Hickman-Lewis, RP Hodyss, BHN Horgan, JR Johnson, JL Jørgensen, LC Kah, JN Maki, L. Mandon, N. Mangold, FM McCubbin, SM McLennan, K. Moore, M. Nachon, P. Nemere, LD Nothdurft, JI Núñez, L. O’Neil,. ..
