The first close-up photograph of layered rocks at the base of the ancient river delta in Jezero Crater holds a special place in the heart of Katie Stack Morgan, assistant project scientist on NASA's Perseverance Mars rover. On April 30, 2022, one of the rover's Hazard Avoidance Cameras (Hazcams) captured a picture of the rocky outcrop known informally as "Enchanted Lake" from a location in Alaska's Katmai National Park and Preserve.
The delta, a large fan-shaped collection of rock and silt that runs along the western side of Jezero Crater, was formed billions of years ago at the meeting point of a Martian river and a crater lake. Stack Morgan and the rest of the Perseverance research team have been looking forward to exploring this delta because they think it offers the best chance of finding rocks that may have preserved traces of ancient microbial life, one of the mission's main objectives.
According to Stack Morgan, the mission's engineers primarily use the hazcam photos to assist in driving and positioning the rover's arm. “However, when I saw the Hazcam footage of Enchanted Lake, I fell in love at first sight. Since Jezero was chosen as the landing site for Perseverance nearly four years ago, this image has given us the first close look at the sedimentary rocks I'd love to examine.”
Rocks and Evidence of Previous Life
To fully understand why Stack Morgan found this photograph, which shows Perseverance's first close contact with a sedimentary rock, so exciting, it's important to start from the beginning of the rover's exploration of Mars. After landing on Mars on February 18, 2021, Perseverance studied outcrops, rocks, and regolith (broken rock and dust) in the area for more than a year. He also collected samples along the route.
The rocks of the crater floor are of igneous origin and formed billions of years ago from molten rock that cooled either underground or after volcanic eruptions; This is one of the most important lessons that the scientific team drew from this study. Much can be learned from the age of geological features and igneous rocks inside Mars. Scientists also discovered evidence that igneous rocks interacted with water and may have supported formerly habitable micro-environments.
But as Stack Morgan points out, the intense heat and pressure that creates igneous rocks don't always provide the best conditions for preserving the fossilized remains of microscopic life.
On the other hand, sedimentary rocks such as those dominant in the Jezero delta offer an excellent location to look for evidence of ancient life.
Jezero used to be a lake that slowly filled with mud, silt, and sand, which over time compacted and consolidated to form thin layers of sedimentary rock. If small organisms were also present during the formation of sedimentary rocks, they may have been trapped within the strata and preserved as fossilized life forms.
Could the stratified rocks of Enchanted Lake be proof that little life once existed on Mars? It's possible. However, for such an important decision, it will be necessary to wait for the samples collected by Perseverance in special tubes to be examined using powerful laboratory instruments that are too large to be sent to Earth and taken to Mars.
While NASA plans to send around 30 tubes back to Earth as part of the Mars Sample Return Campaign, it has to be selective about what to put inside.
We first approached sedimentary rocks at Enchanted Lake in Jezero, but now we're going to do what rover missions do best: look around, crawl, and then explore some more. “Even if we discover other targets to sample in the delta, I will always have a special place in my heart for the rocks that prove we sent the rover to the appropriate place,” Stack Morgan said.
Perseverance is parked almost halfway across the delta, in a vast expanse of sedimentary rock known as the "Hogwallow Flats."
The rover will examine and perhaps sample one or more rocks in the area in the coming weeks. The group will then decide whether to return to Enchanted Lake or explore the more fascinating outcrops of the Jezero delta.
Details of Mars Mission
Astrobiology, including the search for evidence of ancient microbial life, is one of the main goals of Perseverance's mission to Mars. The rover, the first mission to collect and store Martian rocks and regolith, will open the Red Planet to human exploration by describing the planet's geology and historical climate.
Subsequent NASA missions will send spacecraft to Mars in collaboration with ESA (European Space Agency) to collect these sealed samples from the surface and return them to Earth for in-depth examination.
NASA's Moon-to-Mars exploration strategy, which includes the Artemis missions to the Moon to aid preparations for manned exploration of the Red Planet, also includes the Mars 2020 Perseverance mission.