NASA’s Curiosity Finds Organic Molecules Never Seen Before on Mars
After years of lab work, the results are in: A rock that NASA’s Curiosity Mars rover drilled and analyzed in 2020 includes the most diverse collection of organic molecules ever found on the Red Planet. Of the 21 carbon molecules identified in the sample, seven of them were detected for the first time on Mars.
Scientists have no way of knowing whether these organic molecules were created by biological or geological processes – both routes are possible – but their discovery once again confirmed that ancient Mars had the right chemistry to support life. Additionally, these molecules join a growing list of compounds known to be preserved in rocks even after billions of years of exposure on Mars to radiation, which can break down these molecules over time.
The results are detailed in a new paper published Tuesday in Nature Communications.
The rock sample, nicknamed “Mary Anning 3” after an English fossil collector and paleontologist, was collected from a part of Mount Sharp covered by lakes and streams billions of years ago. This oasis arose and dried up several times during the planet’s ancient times, eventually enriching the region with clay minerals, which are particularly effective at preserving organic compounds – carbon-containing molecules that are the building blocks of life and found throughout the solar system.
Among the newly identified molecules is a nitrogen heterocycle, a ring of carbon atoms that includes nitrogen. This type of molecular structure is considered a predecessor of RNA and DNA, two nucleic acids essential for genetic information.
“This detection is quite thorough because these structures may be chemical precursors to more complex nitrogen molecules,” said the paper’s lead author, Amy Williams of the University of Florida in Gainesville. “Nitrogen heterocycles have never before been discovered on the Martian surface nor confirmed in Martian meteorites.”
Another exciting discovery was benzothiophene, a carbon and sulfur-containing molecule found in many meteorites. Some scientists believe that these meteorites, along with the organic molecules they contain, seeded prebiotic chemistry in the early days of the solar system.
The new paper complements last year’s discovery of the largest organic molecules ever discovered on Mars: long-chain hydrocarbons including decane, undecane and dodecane.
“Curiosity and our team are at their best. It took dozens of scientists and engineers to locate this site, drill the sample and make these discoveries with our amazing robot,” said mission project scientist Ashwin Vasavada of NASA’s Jet Propulsion Laboratory in Southern California. “This collection of organic molecules once again increases the prospect that Mars provided a home to life in the ancient past.”
Both sets of discoveries were made with a sophisticated minilaboratory called Sample Analysis at Mars (SAM), located in Curiosity’s belly. A drill at the end of the rover’s robotic arm pulverizes a carefully selected rock sample into powder, then flows it into SAM, where a high-temperature furnace heats the material, releasing gases that the lab’s instruments analyze to reveal the rock’s composition.
Additionally, SAM can perform “wet chemistry,” dropping samples into a small cup of solvent. The resulting reactions can break apart larger molecules that would otherwise be difficult to detect and identify. Although the instrument has several such cups, only two contain tetramethylammonium hydroxide (TMAH), a powerful solution reserved for higher value samples. Mary Anning sample 3 was the first to be exposed to TMAH.
To check TMAH’s reactions with otherworldly materials, the paper’s authors also tested the technique on Earth with a piece of the Murchison meteorite, one of the most studied meteorites of all time. More than 4 billion years old, Murchison contains organic molecules that were seeded throughout the early solar system. A Murchison sample exposed to TMAH was found to break much larger molecules into some of those seen in Mary Anning 3, including benzothiophene. This result verifies that the Martian molecules found in Mary Anning 3 could have been generated from the breakdown of even more complex compounds linked to life.
Curiosity recently used its second and final TMAH cup while exploring web-like ridges formed by ancient groundwater. The mission team will analyze these results for a future peer-reviewed article.
Built by NASA’s Goddard Space Flight Center in Greenbelt, Maryland, SAM is based on larger, commercial-grade laboratory instruments. Incorporating such complex equipment into the rover required engineers to scale it down significantly and develop a way for it to operate with less energy. Scientists had to learn to heat SAM’s furnace more slowly over longer periods of time in order to conduct some of these experiments.
“It was quite an accomplishment to figure out how to do this type of chemistry for the first time on Mars,” said Charles Malespin, principal investigator of the instrument at NASA Goddard and co-author of the study. “But now that we have some practice, we are ready to conduct similar experiments on future missions.”
In fact, NASA Goddard provided several components, including the mass spectrometer, for a next-generation version of the SAM, called the Mars Organic Molecular Analyzer, for ESA’s (European Space Agency) Rosalind Franklin Mars rover. A similar instrument, the Dragonfly mass spectrometer, will explore Saturn’s moon Titan aboard NASA’s Dragonfly rotorcraft. Both instruments will be capable of performing wet chemistry with TMAH solvent.
Curiosity was built by JPL, managed by Caltech in Pasadena, California. JPL is leading the mission on behalf of NASA’s Science Mission Directorate in Washington as part of NASA’s Mars Exploration Program portfolio.
To learn more about Curiosity, visit:
https://science.nasa.gov/mission/msl-curiosity
Contacts with news media
André Bon
Jet Propulsion Laboratory, Pasadena, California.
818-393-2433
andrew.c.good@jpl.nasa.gov
Karen Fox / Alana Johnson
NASA Headquarters, Washington
240-285-5155 / 202-672-4780
karen.c.fox@nasa.gov / alana.r.johnson@nasa.gov
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