Artist concept of NASA's Perseverance, the Mars 2020 rover, drilling a core sample from a rock on the dry lakebed of the Jezero Crater. (NASA/JPL-Caltech)
NASA’s Perseverance rover has successfully collected its first rock samples from Mars’ Jezero Crater, specimens that will help illuminate the geologic and possibly astrobiological history of our planetary neighbor.
The 30-mile-wide Jezero Crater was once a lake, long ago in Mars’ past, and a prime spot to search for chemical residues left behind by any water-dwelling microbes that may have existed.
Though previous Mars missions have analyzed rocks before, Perseverance takes its prospecting a step further by sealing the samples in special titanium tubes that can be retrieved and brought back to Earth by a future mission.
Even as Perseverance makes its way across the Jezero Crater, a joint NASA-European Space Agency Mars Sample Return mission is under development to bring the rock samples back to Earth. MSR will include a rover to collect sample tubes that Perseverance will deposit along its path and a rocket stage that will carry the samples off Mars and back to Earth.
Perseverance is the first mission designed to look for signs of past life on Mars.
Earlier missions such as Curiosity, which is still actively exploring Mars’ Gale Crater, and the twin Spirit and Opportunity rovers have examined past water and environmental conditions friendly to life. Their work revealed an ancient Mars with many Earth-like qualities: a thicker, warmer atmosphere, precipitation, as well as surface rivers, lakes and seas.
But researchers still don’t know if life ever arose in Mars’ watery past. Discovering geological evidence of Martian life would be a pivotal moment not only in the history of science, but in history, period.
Drilling rock to probe the past
On Sept. 6 and 8, Perseverance drilled out two small sample cores from a rock that researchers dubbed "Rochette." After taking pictures of the tubes' contents to ensure the collection was successful, the rover cached the samples away for future analysis on Earth.
The sampled rock may have been formed long ago in a lava flow but has since been chemically and physically altered by the presence of liquid water later in its history. The current condition of the rocks tells scientists the water was present for a long period of time and not merely a fleeting wet spell. Whether the waters persisted for tens of thousands or millions of years is not clear, but it appears to have lasted long enough to maintain an aquatic environment friendly to life.
Researchers have also detected salt minerals, often found in connection to water on Earth, in Jezero’s rocks. Sometimes salt is deposited by groundwater flowing through rock or left behind after water evaporates.
In the months ahead, Perseverance will collect and store up to 43 samples of rock from a wide area of Jezero’s crater floor and walls, deposits spanning millions or billions of years of its history.
Each tiny sample, along with measurements and analysis made around their collection sites, constitutes a small piece of information about Jezero Crater’s history. As Perseverance collects more samples, a detailed understanding of Jezero's past will develop — when it was formed, when water appeared and how long it remained, and with any luck, if anything ever lived there.
Perseverance is currently prospecting a portion of Jezero’s dry lakebed, but later in its mission will visit a variety of terrains, including a large formation of sedimentary deposits carried into the lake by a river, and the lake’s ancient shoreline where shallow water may have provided even more life-friendly habitats.
Searching for signs of life
Perseverance is equipped with a suite of specialized instruments to answer these questions by measuring rock composition, capturing microscopic images and detecting organic compounds. But, as capable as our mobile robotic science laboratories have become, there is still no substitute for the depth of analysis that can be accomplished in laboratories on Earth.
We will not see any discoveries made from Perseverance’s cached rock samples for several years, when the Mars Sample Return mission proceeds, but the potential rewards are worth waiting for.
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