NASA’s Perseverance rover stores rock and soil samples in sealed tubes on the planet’s surface for retrieval by future missions, as seen in this illustration. Credit: NASA/JPL-Caltech
Nestled with every rock and soil sample collected from NASAThe Perseverance rover is a potential boon for atmospheric scientists.
The persistence of NASA Mars the rover collects samples of Mars, including rock cores and atmospheric gases, to eventually be returned to Earth. These samples could provide critical insight into the Martian atmosphere and its evolution, possibly revealing the presence of microbial life billions of years ago. Gas samples, in particular, could offer valuable clues about trace gases and the planet’s ancient climate, drawing parallels with Earth’s own atmospheric history and aiding future manned missions to Mars.
Collection of samples on Mars
With every rock core that NASA’s Perseverance rover seals in its titanium sample 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 taken so far.
Most of these samples consist of rock cores or regolith (crushed rock and dust), which can 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 by the prospect of studying the “headspace,” or the air in the extra room around the rocky material, in the tubes.
They want to learn more about the Martian atmosphere, which is made up mostly of carbon dioxide but may also include traces of other gases that may have been around since the planet formed.
This image shows a rock core about the size of a piece of chalk in a sample tube inserted into the drill bit of NASA’s Perseverance rover. After the rover seals the tube, air will be trapped in the extra space in the tube – seen here in the small gap (called the “headspace”) above the rock. Credit: NASA/JPL-Caltech/ASU/MSSS
Insights from Martian 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. “This will help us understand how climates other than our own develop.”
Among the samples that could be brought back to Earth is a tube filled with gas only, deposited on the surface of Mars as part of a sample depot. But much more of the gas in the rover’s collection is in the upper space of the rock samples. They are unique because the gas will interact with the rocky 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 is moving near the Martian surface, one factor that determines why ice forms where it does on the planet and how the Martian water cycle has evolved over time. .
Seen here is a sealed tube containing a sample of the Martian surface collected by NASA’s Perseverance rover after it was deposited with other tubes in a “sample depot.” Other full sample tubes are stored in the rover. Credit: NASA/JPL-Caltech
Comparing trace gases and ancient atmospheres
Scientists also want a better understanding of the trace gases in the Martian air. Most scientifically enticing would be the discovery of noble gases (such as neon, argon, and xenon) that are so unreactive that they may have existed unchanged in the atmosphere since they formed billions of years ago. If captured, these gases could reveal whether Mars had an atmosphere to begin with. (Ancient Mars had a much denser atmosphere than today’s, but scientists aren’t sure if it was always there or if it developed later.) There are also big questions about how the planet’s ancient atmosphere compares to early Earth.
The headspace would further provide an opportunity to assess the size and toxicity of the 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 would be interested because it will shed light on how planets form and evolve.”
Apollo air tests
In 2021, a group of planetary explorers, including NASA scientists, examined the air brought back from the Moon in a steel container by the Apollo 17 astronauts some 50 years ago.
“People think of the Moon as airless, but it has a very thin atmosphere that interacts with the lunar surface rocks over time,” said Simon, who studies various planetary samples at Johnson. “This involves the outflow of noble gases from the interior of the Moon and collection on the lunar surface.”
Laboratory techniques for gas analysis
The way Simon’s team extracts the gas for study is similar to what might be done with Perseverance’s air samples. First, they place the previously unopened container in a hermetically sealed box. They then punctured the steel with a needle to extract the gas into a cold trap—essentially a U-shaped tube that extends into a liquid, such as nitrogen, with a low freezing point. By changing the temperature of the liquid, the scientists 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 manipulate the gas in this way,” Simon said. In addition to being used to study the origin of planetary materials, this approach could be applied to gases from hot springs and those emitted from the walls of active volcanoes, he added.
Of course, these sources provide far more gas than Perseverance has in its sample tubes. But if one tube doesn’t carry enough gas for a particular experiment, Mars scientists can combine gases from multiple tubes to get a larger aggregate sample — another way overhead space offers a bonus opportunity for science.
NASA’s Perseverance 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 Jezero Crater, Perseverance has a primary mission of searching for signs of ancient life and collecting rock and regolith (crushed rock and soil) samples for eventual return to Earth .
