After 1,000 days on Mars, NASA’s Perseverance rover on its mission traveled through an ancient system of rivers and lakes, collecting valuable samples along the way.
Reaching its 1,000th Martian day on the Red Planet, NASA’s Perseverance rover recently completed its exploration of the ancient river delta that contains evidence of a lake that occupied Jezero Crater billions of years ago. The six-wheeled scientist has so far collected a total of 23 samples, revealing the geological history of this region of Mars in the process.
A sample called “Lefroy Bay” contains a large amount of fine-grained silica, a material known to preserve ancient fossils on Earth. Another, “Pico Otis,” has a significant amount of phosphate, often associated with life as we know it. Both samples are also rich in carbonate, capable of preserving a record of environmental conditions since the rock’s formation.
The findings were shared Tuesday, Dec. 12, at the American Geophysical Union’s fall meeting in San Francisco.
“We chose Jezero Crater as the landing site because orbital images showed a delta – clear evidence that a large lake once occupied the crater. A lake is a potentially habitable environment, and deltaic rocks are a great environment for preserving signs of ancient life like fossils in the geological record,” said Perseverance project scientist Ken Farley of Caltech. “After detailed exploration, we were able to reconstruct the geological history of the crater, mapping its lake and fluvial phases from beginning to end.”
Jezero formed from an asteroid impact almost 4 billion years ago. After Perseverance landed in February 2021, the mission team discovered that the crater floor is composed of igneous rock formed from underground magma or from volcanic activity on the surface. Since then, they have found sandstone and mudstone, indicating the arrival of the first river in the crater hundreds of millions of years later. Above these rocks are salt-rich mudstones, signaling the presence of a shallow lake that was undergoing evaporation. The team believes the lake eventually reached up to 35 kilometers in diameter and 30 meters in depth.
This conceptual animation by an artist depicts water breaching the rim of Mars’ Jezero Crater, which NASA’s Perseverance rover is currently exploring. Water entered the crater billions of years ago, forming a lake, delta and rivers before the Red Planet dried up.
Later, fast-flowing water brought rocks from outside Jezero, distributing them across the top of the delta and elsewhere in the crater.
“We were able to see a broad outline of these chapters in Jezero’s history in orbital images, but it took getting up close with Perseverance to really understand the timeline in detail,” said Libby Ives, a postdoctoral researcher at the Space Propulsion Laboratory. NASA jet in Southern California, which manages the mission.
The samples collected by Perseverance are approximately the size of a piece of classroom chalk and are stored in special metal tubes as part of the Mars Sample Return campaign, a joint effort by NASA and ESA (European Space Agency). Bringing the tubes to Earth would allow scientists to study the samples with laboratory equipment too powerful to take to Mars.
To decide which samples to collect, Perseverance first uses an abrasion tool to abrade an area of a prospective rock and then studies the rock’s chemistry using precision scientific instruments, including the Planetary Instrument for X-ray Lithochemistry (PIXL), built by the JPL.
In a target that the team calls “Bills Bay”, PIXL detected carbonates – minerals that form in aqueous environments with favorable conditions for preserving organic molecules. (Organic molecules form by both geological and biological processes.) These rocks were also abundant in silica, an excellent material for preserving organic molecules, including those related to life.
“On Earth, this fine-grained silica is what you often find in a place that was once sandy,” said JPL’s Morgan Cable, PIXL deputy principal investigator. “It’s the kind of environment where, on Earth, the remains of ancient life could be preserved and found later.”
Perseverance’s instruments are capable of detecting microscopic fossil-like structures and chemical changes that may have been left behind by ancient microbes, but they have not yet found evidence of either.
In another target examined by PIXL, called “Cachoeiras Ouzel”, the instrument detected the presence of iron associated with phosphate. Phosphate is a component of the DNA and cell membranes of all known terrestrial life and is part of a molecule that helps cells transport energy.
After evaluating PIXL’s findings at each of these abrasion points, the team sent commands to the rover to collect nearby rock cores: Lefroy Bay was collected next to Bills Bay and Otis Peak at Ouzel Falls.
“We have ideal conditions for finding signs of ancient life where we find carbonates and phosphates, which point to a habitable aqueous environment, as well as silica, which is great for preservation,” Cable said.
Perseverance’s work is, of course, far from over. The mission’s fourth ongoing science campaign will explore the rim of Jezero Crater, near the canyon entrance where a river flooded the crater floor. Carbonate-rich deposits have been spotted along the shore, which stand out in orbital images like a ring inside a bathtub.
A key objective of Perseverance’s Mars mission is astrobiology, including the search for signs of ancient microbial life. The rover will characterize the planet’s geology and past climate, pave the way for human exploration of the Red Planet, and be the first mission to collect and store Martian rocks and regolith.
Subsequent NASA missions, in cooperation with ESA (European Space Agency), will send spacecraft to Mars to collect these sealed surface samples and bring them to Earth for more detailed analysis.
The Perseverance Mars 2020 mission is part of NASA’s Moon-to-Mars exploration approach, which includes Artemis missions to the Moon that will help prepare for human exploration of the Red Planet.
JPL, managed by Caltech in Pasadena, California, built and operates the Perseverance rover.
For more information about Perseverance: mars.nasa.gov/mars2020/
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2023-12-18 03:42:22
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