After 13 years roaming Mars, NASA’s Curiosity rover conducts a rare experiment with advanced chemistry and makes a final attempt to detect molecules linked to ancient life

After 13 years of operations on Mars, NASA’s Curiosity rover began a rare chemical experiment, using the last dose of a special solvent to analyze rocks formed in a water environment—a step considered critical to expanding our understanding of organic compounds on the planet.

NASA’s Curiosity rover began a rare experiment on Mars on February 2nd, using the final dose of a special chemical reagent to analyze a rock sample for possible organic compounds, after a period of conjunction and 13 years of operations on the planet.

NASA’s Curiosity rover and the rare chemical experiment on Mars.

NASA’s Curiosity rover began performing an unusual type of scientific experiment after Mars exited conjunction, a period when communication with spacecraft is interrupted because the planet is behind the Sun from Earth’s perspective. This procedure had only been performed once before during the mission.

The experiment uses a solvent called tetramethylammonium hydroxide, known as TMAH in methanol. The liquid is mixed with pulverized rock to facilitate the detection of certain carbon-based molecules associated with chemical processes related to known life on Earth.

NASA’s Curiosity rover’s onboard laboratory carried only two small containers of this solvent during the entire mission. One of them had been used about six years ago, making the current analysis the last opportunity to employ the specific chemical compound.

Planning and risk reduction in test execution.

Prior to the final execution, the scientific team conducted detailed tests to minimize operational risks. The tests included simulating the transfer of the sample to the rover’s chemical laboratory, as recorded in mission reports.

“We want to be absolutely sure that everything goes well,” said Alex Innanen, an atmospheric scientist at York University, in an official statement. According to him, the team conducted a full rehearsal of the sample delivery procedure.

The technique offers the possibility of identifying chemical clues that standard methods may not detect. Identifying these molecules helps researchers assess whether Mars ever presented conditions compatible with the presence of life and how chemical processes similar to those on Earth may arise on other worlds.

Previous results and recent scientific context

Organic compounds have been identified on Mars before, although the scientific significance of these detections is still under analysis. In September, NASA announced that a sample collected by the Perseverance rover contained fossilized material that could have been produced by ancient microorganisms.

According to Nicky Fox, associate administrator of the agency, this finding represents the closest approximation to date to the identification of ancient life on Mars. However, officials stressed that non-biological explanations cannot yet be ruled out.

Images obtained by the Mars Reconnaissance Orbiter have revealed formations known as boxwork on the planet. These structures, visible from orbit, are being investigated directly by NASA’s Curiosity rover on the Martian surface.

Collection site and geological characteristics of the sample.

The sample analyzed was collected from a location near a borehole drilled in November, called Nevado Sajama. The region contains fine-grained sedimentary rocks, considered to have formed a long time ago under conditions involving water.

This type of environment is considered favorable for the preservation of fossilized organic materials. The past presence of water makes the site relevant for scientific research, since aqueous environments are associated with chemical processes essential to known life.

To avoid mistakes, the team practiced each step of transferring the material to the rover’s chemical laboratory beforehand. The formal start of the experiment took place on Monday, February 2nd, according to Ashwin Vasavada, a scientist on NASA’s Curiosity project.

Previous experiments with TMAH and reformulation of the method

The last use of TMAH occurred in 2020, when NASA’s Curiosity rover drilled into a clay-rich rock called Mary Anning. Analysis of the results took about seven months and revealed a greater variety of organic molecules than methods based solely on heating.

These results offered a more detailed view of the complex chemistry of Gale Crater. Scientists continue to assess whether some of these molecules could originate from components of the rover itself, which requires caution in interpreting the data.

After the initial test, researchers at the Goddard Space Flight Center decided to redesign the experiment. The goal was to adjust the interaction of the solvent with the Martian sediment and bring the procedure closer to analyses performed in terrestrial laboratories.

The new method divides the experiment into three stages, allowing the solvent to interact with the sediment at different temperatures. Development took several years and suffered delays due to the COVID-19 pandemic.

Timing and relevance of clays

With the redesign finalized, the team awaited a suitable opportunity to conduct the experiment. The discovery of clay minerals in the boxwork region led the scientists to consider the location appropriate for the final use of TMAH.

Clay minerals can contribute to the preservation of organic material over time. According to Vasavada, the combination of this discovery with favorable signals from the initial borehole at Nevado Sajama convinced the mission that the site was suitable for the final test.

Since its launch in 2011, NASA’s Curiosity rover has traveled more than 352.000.022 miles, with 352 million miles during its space journey and another 22,5 million on the Martian surface, traversing deserts and diverse geological formations.

Boxwork region and remaining solvents

Last year, the rover explored an extensive boxwork region, characterized by networks of low ridges that resemble spider webs when viewed from space. Scientists suggest that these structures may have formed with the last flows of groundwater before the area definitively dried up.

Of NASA’s Curiosity rover’s 74 internal compartments, nine contained solvents intended for wet chemistry experiments when the rover landed in 2012. Although TMAH has been fully utilized, compartments containing another solvent, known by the acronym MTBSTFA, still remain.

Two of the three phases of the current experiment have already been completed, according to Vasavada. He stated that the team is eager for the results, but stressed that the analysis is complex and will require several months for scientists to have confidence in what has been found, even with a slight delay in data interpretation.