NASA's Perseverance rover is seeing Mars in a new light.
A state-of-the-art instrument called SHERLOC, which hunts for molecules possibly related to ancient life, played a key role in a recent study.
In its first 400 days on Mars, NASA’s Perseverance rover will have found a diverse collection of organisms — the carbon-based molecules thought to be the building blocks of life — thanks to SHERLOC, an innovative instrument on the rover’s robotic arm. Scientists with the mission, which is looking for evidence that the planet supported microbial life billions of years ago, aren’t sure whether biological or geological sources formed the molecules, but they are intrigued.
Short for scanning habitable environments with Raman and light for organics and chemicals, SHERLOC helps scientists decide if a sample is worth collecting. This instrument makes it essential for the Mars sample return mission. The Perseverance rover is the first step in the mission, a joint effort between NASA and ESA (the European Space Agency) to return scientifically selected samples from Mars to Earth for study with laboratory equipment that is far more complex than those sent to the Red Planet. Samples will need to be returned to confirm the presence of organic matter.
SHERLOC’s capabilities center on a technique that looks at the chemical makeup of rocks by analyzing how they scatter light. This device directs an ultraviolet laser at its target. How this light is absorbed and then emitted — a phenomenon known as the Raman effect — provides a distinctive spectral “fingerprint” of different molecules. It enables scientists to classify the organic and mineral elements in rock and to understand the environment in which the rock formed. For example, salt water can have a different mineral composition than fresh water.
When SHERLOC captures rock textures with its WATSON (Wide-Angle Topographic Sensor for Operations and Engineering) camera, it adds data to those images to create spatial maps of chemicals on the rock surface. The results, detailed in a recent paper in Nature, were as promising as the instrument’s science team had hoped.
“These results are an exciting example of what SHERLOC can find, and they’re helping us understand how to find the best samples,” said lead author Sunanda Sharma of NASA’s Jet Propulsion Laboratory in Southern California. JPL teamed up with the Perseverance rover to build SHERLOC.
NASA’s Curiosity rover, which landed on Mars in 2012, has repeatedly confirmed the presence of organic molecules in Gale Crater, 2,300 miles (3,700 km) away. Curiosity relies on SAM, or Sample Analysis on Mars, an instrument in its belly that heats powdered rock samples and performs chemical analysis on the resulting vapors.
As persistent scientists search for rocks that may preserve traces of ancient microbial life, they want to preserve samples for closer study on Earth.
Reaching the center
The new Nature paper looks at 10 rock targets studied by SHERLOC, including one nicknamed “Quartier”.
“We see a set of signals that are consistent with organics in the Quaternary data,” Sharma said. “He got everyone’s attention.”
When the data coming back from SHERLOC and other instruments looks promising, the science team decides whether to use the rover’s drill to cover a rock sample the size of a classroom chalk. After analyzing Quartier, they took rock core samples “Robine” and “Malay” from the same rock – two of the 20 core samples collected so far (learn more with the sample dashboard).
Choosing a good target for sample collection is not as simple as finding the most organic molecules. Ultimately, Persistence scientists want to collect a collection of samples that is representative of all the different fields that are found inside Jezero Crater. This breadth will provide context for future scientists studying these artifacts, who will wonder what changes occurred around any artifacts that might indicate signs of ancient life.
“Value comes from the sum rather than the individual pattern,” Sharma said. “Pointillism is a good analogy for that. We will eventually step back and look at the bigger picture of how this area is formed.