NASA’s Perseverance Mars rover stores rock and soil samples in sealed tubes on the planet’s surface for future missions to retrieve, as seen in this image. Credit: NASA/JPL-Caltech
Tucked away with every rock and soil sample he collected NASAThe Perseverance rover is a potential boon for atmospheric scientists.
NASA persistence Mars the rover collects samples on Mars, including rock cores and atmospheric gases, to eventually return to Earth. These samples may provide critical insight into the Martian atmosphere and its evolution, possibly revealing the presence of microbial life billions of years ago. In particular, the gas samples could offer valuable data about the planet’s trace gases and ancient climate, drawing parallels with Earth’s own atmosphere and helping future manned missions to Mars.
Mars Sample Collection
With every rock core NASA’s Perseverance Mars rover seals in its titanium tubes, atmospheric scientists get a little more excited. These samples are being collected for eventual delivery to Earth as part of the Mars Sample Return campaign, with twenty-four collected so far.
Most of these samples consist of rock cores or regolith (broken rock and dust), which could reveal important information about the planet’s history and whether microbial life was present billions of years ago. But some scientists are just as excited about the prospect of studying the “head space,” or air in the extra room around the rocky material in the tubes.
They want to learn more about the Martian atmosphere, which is mostly carbon dioxide but could also contain trace amounts of other gases that may have been around since the planet’s formation.
This image shows a rock core about the size of a piece of chalk in a sample tube located in the drill bit of NASA’s Perseverance Mars probe. Once the rover seals the tube, the air is trapped in a special space in the tube – seen here in a small gap (called “headspace”) above the rock. Acknowledgments: NASA/JPL-Caltech/ASU/MSSS
Observations from Mars Headspace
“Air samples from Mars will tell us not only about the current climate and atmosphere, but also how it has changed over time,” said Brandi Carrier, a planetary scientist at NASA’s Jet Propulsion Laboratory (JPL) in Southern California. “It will help us understand how climates different from our own evolve.”
Among the samples that could be brought to Earth is one tube filled entirely with gas stored on the surface of Mars as part of a sample repository. But much more of the gas in the rover’s collection is in the upper space of the rock samples. These are unique because the gas will interact with the rock material inside the tubes for years before the samples can be opened and analyzed in laboratories on Earth. What scientists gather from them will provide insight into how much water vapor floats near the surface of Mars, one of the factors that determines why ice forms on the planet and how the Martian water cycle has evolved over time.
Seen here is a sealed tube containing a sample of the surface of Mars collected by NASA’s Perseverance Mars rover after it was stored with other tubes in a “sample repository.” Additional filled sample tubes are stored in the rover. Credit: NASA/JPL-Caltech
A comparison of trace gases and ancient atmospheres
Scientists also want to better understand trace gases in the air on Mars. Most scientifically impressive would be the detection of noble gases (such as neon, argon, and xenon) that are so unreactive that they may have been in the atmosphere unchanged since their formation billions of years ago. If these gases were captured, they could reveal whether Mars began with an atmosphere. (Ancient Mars had a much denser atmosphere than today, but scientists aren’t sure if it was always there or if it developed later). There are also big questions about how ancient the planet’s atmosphere is compared to early Earth.
In addition, headspace would provide the ability to assess the size and toxicity of dust particles—information that will help future astronauts on Mars.
“Gas samples have a lot to offer Mars scientists,” said Justin Simon, a geochemist at NASA’s Johnson Space Center in Houston who is part of a group of more than a dozen international experts helping decide which samples the rover should collect. “Even scientists who don’t study Mars will be interested because it will shed light on how planets form and evolve.”
Apollo air samples
In 2021, a group of planetary researchers, including NASA scientists, studied air brought back from the Moon in a steel container by Apollo 17 astronauts some 50 years earlier.
“People think the moon is airless, but it has a very thin atmosphere that interacts with rocks on the lunar surface over time,” said Simon, who studies various planetary samples at Johnson. “This includes rare gases that escape from the interior of the moon and collect on the lunar surface.”
Laboratory techniques for gas analysis
The way Simon’s team extracted the gas for study is similar to what can be done with Perseverance’s air samples. First, they put the previously unopened container into an airtight seal. They then pierced the steel with a needle to extract the gas into the cryogenic paste—essentially a U-shaped tube that runs into a low-freezing liquid like nitrogen. By changing the temperature of the liquid, the researchers trapped some of the gases with lower freezing points at the bottom of the cold trap.
“There are maybe 25 labs in the world that handle gas this way,” Simon said. In addition to being used to study the origin of planetary materials, the approach can be applied to gases from hot springs and gases emitted from the walls of active volcanoes, he added.
Of course, these sources provide far more gas than Perseverance has in its tubes. But if one tube doesn’t carry enough gas for a particular experiment, Mars scientists could combine gases from multiple tubes to get a larger aggregate sample — another way overhead space offers a bonus opportunity for science.
NASA’s Perseverance Mars Rover
NASA’s Perseverance rover, part of the Mars 2020 mission, is a sophisticated mobile laboratory designed to explore the surface of Mars. Launched on July 30, 2020 and landing on Mars on February 18, 2021 in Crater Lake, Perseverance’s primary mission is to search for signs of ancient life and collect rock and regolith (broken rock and soil) samples for possible return to Earth.