Mars Rover Perseverance: A Journey of Discovery
On this momentous day, NASA enthusiastically recalls the exploration of the ancient river delta by the Mars Rover Perseverance. Over the course of its journey, the rover has gathered numerous invaluable samples.
It was February 18, 2021, when the Mars Rover Perseverance first set its wheels on the Mars surface. Since that time, this sophisticated wanderer has tirelessly explored the Jezero crater, with its central mission being to discover evidence of life from epochs long past. However, today is a moment – both literally and figuratively – to stand still and take stock of its journey. Remarkably, Perseverance has now spent 1000 Martian days, or ‘sols’, on the red planet, a significant milestone.
While Perseverance celebrated its 1000th sol on the Red Planet, it also recently completed its exploration of the ancient Jezero river delta, a river delta that provides evidence for a lake that filled the crater billions of years ago.
The Jezero Crater
“We chose the Jezero crater as the landing site because images revealed that this crater was once filled with water,” explains team member Ken Farley. “A lake provides potentially habable conditions and the delta’s sedimentary rocks create an ideal environment for preserving traces of past life, like fossils. After thorough exploration, we have accurately mapped the crater’s geological history, tracking step by step the different phases of the lake and the river, from the early beginnings to its end.”
Geological History
The Jezero crater was formed around four billion years ago by the impact of an asteroid. After Perseverance landed in February 2021, the mission team discovered that the crater’s floor largely consisted of igneous rock that had either formed underground or surfaced through volcanic activity. Later, they discovered sandstone and mudstone, suggesting that a river emerged a few hundred million years after the crater was formed. Above these rocks reside mudstones with a high salt content, which indicates that an ancient shallow lake that slowly evaporated was once present. The team suspects this lake eventually reached a diameter of up to 35 kilometers and a maximum depth of 30 meters. Later on, swift flowing waters brought boulders from outside Jezero and scattered them across the delta and other parts of the crater.
Thanks to Perseverance
Our current understanding of the Jezero crater can be largely attributed to the tireless work of Perseverance. As team member Libby Ives points out, “While orbital images gave us a general idea of Jezero’s history, it was crucial for Perseverance to get up close and personal to understand the timeline in detail.”
Sampling
Moreover, the advantage of a roving rover is that Perseverance could collect samples in situ. To date, the rover has collected 23 samples. To decide which samples to collect, Perseverance first uses a grinder to shave off a piece of rock. It then studies the rock’s chemical composition with precise instruments, including the Planetary Instrument for X-ray Lithochemistry (or PIXL) developed by JPL. It is through these methods that Perseverance has been able to unearth much about Mars.
Lefroy Bay Sample
A sample named ‘Lefroy Bay’, for instance, contains a great deal of fine-grained silica – a substance known on Earth for fossil preservation. “On Earth, this type of fine-grained silica is often found in places that were once sandy,” explains deputy principal investigator for PIXL, Morgan Cable. “This is a location on Earth where remnants of past life forms could possibly be preserved and discovered later.” This sample was collected in a place researchers call Bills Bay. The area revealed carbonates – minerals formed in water-rich environments that provide favorable conditions for preserving organic molecules (which are generated both by geological and biological processes). The rocks here also contain abundant amounts of silica, a material that’s exceptionally good at preserving organic molecules, including those related to life.
Otis Peak Sample
On the contrary, another collected sample named ‘Otis Peak’ contains a significant amount of phosphate, which is often associated with life as we know it. Phosphate is a building block of DNA and the cell membranes in all known forms of life on Earth. It’s also a component of a molecule that helps cells carry energy. This sample was collected at a location the researchers call ‘Ouzel Falls’. Here, PIXL found iron coupled with phosphate. Both Otis Peak and Lefroy Bay are also formed of carbonate, which could contain information about the conditions under which the rocks were formed.
Perseverance’s instruments are capable of detecting tiny fossil-like structures and chemical changes that may have been left by ancient microbes. So far, however, the mission team has not yet found proof of either. Yet, the researchers remain hopeful. “We have a good chance of finding signs of ancient life in places where we see carbonates and phosphates, pointing to a water-rich and habitable environment,” says Cable. “The presence of silica can also help preserve organic molecules.”
What’s Next for Perseverance?
Even after 1000 Martian days, Perseverance’s work is far from over. In the rover’s fourth scientific phase, it will examine the area on the edge of the Jezero crater, close to the entrance of the canyon where a river once overflowed the crater floor. Along the edge, many carbonate deposits have been observed; from space, they look like rings in a bathtub. This is a clear indication that there is still much to discover about our ever-mysterious neighboring planet, Mars!
