Five of the best discoveries aboard NASA’s Curiosity rover on Mars

Uncovering the potentially habitable climate of ancient Mars is an important part of NASA’s mission to explore and understand the unknown, to inspire and empower humanity – and for 10 years the Red Planet’s Curiosity rover has been involved in the case .

To mark the occasion, here are five of the most significant discoveries scientists have made using Curiosity’s Sample Analysis at Mars (SAM) instrument suite. SAM is one of NASA’s most powerful astrobiological instruments on Mars. Designed and built at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, SAM seeks out and measures organic molecules and light elements essential to life as we know it. To accomplish this task, SAM carries components that remote scientists use to test samples from Mars.

1. Detection of organic compounds on Mars

Charles Malespin and Amy McAdam, SAM’s senior and deputy principal investigators at Goddard, agree on SAM’s most significant discovery: SAM detected organic molecules in rock samples collected from Mars’ Gale Crater. Organic molecules (those containing carbon) could be used as building blocks and “food” for life. Their presence on Mars suggests that the planet might have once supported life if it had ever been there.

While the isotopes in carbon dioxide and methane measured during some SAM sample analyzes may be consistent with ancient biological activity producing the observed organic matter, there are also non-life-based explanations — for example, this isotope signal could be the result of an interaction between ultraviolet light from the sun and carbon dioxide in the Martian atmosphere, creating organic matter that falls to the surface, no life required.

Taken together, these results motivate ongoing and future studies using SAM and the full Curiosity suite of instruments, as well as other planetary missions looking for evidence of habitable environments and life beyond Earth.

2. Methane variability

Using SAM’s tunable laser spectrometer, developed at NASA’s Jet Propulsion Laboratory in Southern California, scientists have detected variations in methane concentration in the near-surface atmosphere where Curiosity collects samples. On Earth, most of the methane present in the atmosphere gets there through life processes and varies due to changes in biological processes, but we don’t know if this is the case on Mars.

Curiosity is unable to determine whether or not the discovered methane originates from biological processes, but the Red Planet’s numerous missions piece together the tantalizing puzzle.

3. Rock formation and exposure age in Gale Crater

Curiosity had been on Mars just over a year when scientists used SAM to determine both the formation and exposure ages of rocks on another planet’s surface for the first time.

The rocks around the rim of Gale Crater were formed about 4 billion years ago and then transported to Yellowknife Bay as sediments. “This is where they were buried and became sedimentary rock,” McAdam said. From there, weathering and erosion slowly collapsed, exposing the rocks to surface radiation about 70 million years ago. Aside from providing insight into Martian erosion rates, knowing how long a sample was exposed allows scientists to consider possible radiation-induced changes in organic compounds that could affect the ability to identify potential biosignatures.

“The age-dating experiment was not planned before it started,” McAdam said. “But the flexibility in the design and operation of SAM and the dedication of a team of scientists and engineers made it possible to carry it out successfully.”

4. Delve into the history of water on Mars

SAM has also shed light on Mars’ wetter past and how the planet has dried out. Water is vital to life as we know it, and “several lines of evidence suggest that the rocks of Gale Crater have a rich water history,” Malespin said. Part of that evidence is the presence of jarosite, a reddish-yellow mineral only formed in aqueous environments, McAdam said. An age-dating experiment using SAM and another Curiosity instrument (APXS) found jarosite to be hundreds of millions of years younger than expected.

This finding suggests that even as much of the Martian surface became dry, some subsurface liquid water remained in the vicinity of Gale Crater, extending the habitability period for any Martian microbes that might be present.

In addition, analysis by SAM provided insight into the loss of the Martian atmosphere that led to its long-term evolution from the early warm and wet state to the current cold and dry state. water, h₂O, contains two hydrogen atoms and one oxygen atom. The hydrogen can be exchanged for a heavier form of itself, deuterium. By measuring the ratio of deuterium to hydrogen in its samples, Curiosity uncovered evidence of a history of hydrogen eruption and water loss on Mars.

5. Biologically useful nitrogen

On Earth, nitrogen is an essential part of the recipe for life – but not just any nitrogen is suitable. In order for most biological processes to use them, the nitrogen atoms must first be “fixed”: freed from their strong tendency to only interact with themselves. “Fixed nitrogen is required for the synthesis of DNA, RNA and proteins,” Malespin said. “These are the building blocks of life as we know it.”

SAM detected fixed nitrogen in the form of nitrate in rock samples it analyzed in 2015. The finding suggested that 3.5 billion years ago biologically and chemically usable nitrogen was present on Mars.

“While this nitrate could have formed early in Mars’ history from thermal shocks from meteorite impacts,” McAdam said, “it’s possible some are forming in the Martian atmosphere today.”

No finding from SAM or Curiosity’s other instruments can provide positive evidence for past life on Mars, but most importantly, these discoveries don’t rule it out. Earlier this year, NASA extended Curiosity’s mission to at least 2025, allowing the rover and its mobile SAM chemistry lab to focus on the tantalizing question of Mars’ habitability.

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