NASA’s Curiosity rover has identified the widest variety of organic molecules ever detected on Mars, including seven compounds never before observed on the planet.

These carbon-based substances are the fundamental ingredients that allowed life to arise on Earth.

The findings, reported Tuesday in the journal Nature Communications, stem from a groundbreaking experiment conducted directly on Mars. For the first time, the rover collected a rock sample and dissolved it in a chemical solution to reveal hidden details about its composition.

According to the research team, the organic compounds discovered in the rock may have been preserved for approximately 3.5 billion years. The study’s lead author, Dr. Amy Williams, an associate professor of geological sciences at the University of Florida and a member of the Curiosity science team, emphasized the importance of the discovery.

“These results matter because they show that larger, more complex organic material can survive on Mars across vast geological timescales, despite the planet’s intense radiation,” Williams explained. “That strengthens the case for ancient habitable environments — places where life could have thrived if it ever emerged.”

The new findings build on Curiosity’s earlier detections of organic compounds and reinforce the idea that Mars was once a potentially habitable world billions of years ago, rather than the cold, arid landscape we see today.

“For me, the real revelation isn’t just that Mars was habitable,” said Ashwin Vasavada, Curiosity’s project scientist at NASA’s Jet Propulsion Laboratory. “It’s how remarkably habitable it appears to have been.”

The wet chemistry experiment was not designed to determine whether the molecules are evidence of ancient Martian life. The compounds could have formed through geological processes or arrived via meteorite impacts.

However, the study highlights a key objective shared by many planetary scientists: to conclusively determine whether life ever existed on Mars, samples must be returned to Earth for detailed analysis.

Seeking the perfect target

Curiosity touched down inside Gale Crater in 2012 with a mission to assess whether Mars once offered conditions suitable for life. Over the years, the rover climbed Mount Sharp, a central peak within the crater, aiming to reach clay-rich layers previously identified from orbit.

Clay minerals are known for their ability to preserve organic matter. Their presence suggested that water once existed in the region and that wet conditions may have fluctuated over time.

After six to seven years of travel, Curiosity reached the clay-bearing region known as Glen Torridon. The journey proved worthwhile, Vasavada said, as the rover uncovered mudstones formed in ancient lakes and sandstone shaped by streams that once flowed into them.

Scientists carefully selected the most promising drilling site for testing organic content. Because the rover carries only two wet chemistry cups, the team needed to choose wisely. They ultimately selected a location named Mary Anning, honoring the pioneering 19th-century British paleontologist.

In 2020, Curiosity drilled into a clay-rich sandstone sample, crushed it into powder, and delivered it to the Sample Analysis at Mars (SAM) instrument housed within the rover.

SAM can heat samples in a miniature oven and analyze gases released as minerals break down under high temperatures. The instrument has previously played a key role in identifying organic chemistry on Mars.

For this experiment, the rover added the powdered sample to a cup containing tetramethylammonium hydroxide (TMAH). This chemical solution helps break apart large, complex molecules, making it easier to detect compounds that might otherwise remain hidden, Williams explained.

The team identified 21 organic molecules containing carbon. Among them was a nitrogen heterocycle — a ring-shaped structure made of carbon atoms and nitrogen. Such structures are considered chemical precursors to RNA and DNA, the molecules that carry genetic information.

“That detection is particularly significant because these ring structures can serve as stepping stones to more complex nitrogen-based molecules,” Williams said. “Nitrogen heterocycles have never before been confirmed on the Martian surface or in Martian meteorites.”

The analysis also revealed benzothiophene, a molecule containing carbon and sulfur that is commonly found in meteorites. Similar material may have been delivered to early Earth, contributing to the ingredients necessary for life.

“The same types of material that fell to Mars from meteorites also fell to Earth,” Williams noted. “On our planet, those ingredients likely played a role in the emergence of life.”

To validate the results, researchers conducted laboratory tests on Earth using a fragment of the Murchison meteorite, which is rich in organic compounds. When treated with TMAH, the meteorite’s larger molecules broke down into compounds resembling those identified in the Mary Anning sample, including benzothiophene.

The Murchison meteorite, discovered in Australia in 1969, is more than 4 billion years old and contains a diverse array of organic material.

Answering a profound question

Over the past year, Curiosity has detected the largest organic molecules yet found on Mars, while NASA’s Perseverance rover has identified intriguing rock features that may point to ancient microbial activity. Together, these discoveries are helping scientists reconstruct a more detailed picture of Mars’ distant past, Vasavada said.

“Even without being an organic chemist, seeing such a wide variety of organic molecules suggests we’re only glimpsing a fraction of what once existed,” he said.

The successful wet chemistry experiment also sets the stage for future missions that will employ similar techniques to search for organic compounds elsewhere in the solar system.

The European Space Agency’s Rosalind Franklin rover, scheduled to explore a different Martian region later this decade, and NASA’s Dragonfly mission to Saturn’s moon Titan will both carry wet chemistry capabilities.

“Designing and executing this type of chemical experiment on Mars was a major achievement,” said Charles Malespin, principal investigator for SAM at NASA’s Goddard Space Flight Center. “Now that we’ve demonstrated it can work, we’re better prepared to apply these methods on future missions.”

The discovery shows that sedimentary rocks on Mars can safeguard traces of organic material for billions of years, said Dr. Briony Horgan, a professor of planetary sciences at Purdue University who was not involved in the study.

“We can’t yet conclude that these molecules were produced by life,” Horgan said. “But we’re steadily gathering the evidence needed to address that possibility.”

Ultimately, scientists agree that returning Martian samples to Earth is essential to definitively determine whether these organics signal ancient life. Detailed laboratory studies on Earth would provide the precision and range of analysis currently impossible on Mars.

Vasavada, reflecting on decades of exploration focused on water and habitability, believes that bringing samples home is the critical final step.

“This long-running effort was always meant to culminate in a definitive test of whether life ever existed,” he said. “To truly answer that question, we need those samples back on Earth.”