A sample from Mars could reveal whether life once existed beyond Earth
A rock collected by NASA’s Perseverance rover contains unusual mineral patterns that may point to ancient microbial activity on Mars. Scientists consider the discovery a major opportunity to investigate life beyond Earth, but confirming its origin will require bringing the sample back for detailed laboratory analysis.
The hunt for alien life has hit a pivotal phase following the identification of a unique geological structure within Jezero Crater, a prehistoric Martian basin carved by liquid water ages ago. Gathered by NASA’s Perseverance rover, the specimen—designated as Sapphire Canyon—features tiny, light-colored patterns that bear a striking resemblance to signatures linked to biological activity on Earth.
Although the discovery has generated considerable scientific interest, researchers have not established that the rock contains evidence of life. Its unusual characteristics could also have developed through nonbiological chemical reactions. Determining which explanation is correct will require more sophisticated tests than the rover can perform on the Martian surface.
The challenge is that the sample remains on Mars, while NASA’s original plan to transport the collected material to Earth was canceled after years of rising costs and technical complications. As scientists continue examining alternative approaches, the possibility of answering one of humanity’s oldest questions depends on the future of Mars sample-return missions.
An unusual rock discovered within a long-gone Martian riverbed
In July 2024, Perseverance secured the Sapphire Canyon specimen from a geological formation known as Cheyava Falls, situated close to Neretva Vallis. Water was once channeled by this valley toward a prehistoric lake inside Jezero Crater, an ecosystem that thrived over 3 billion years ago.
NASA sent the rover to this region in February 2021 because its geological history made it a promising location to search for signs of ancient life. Water is essential to life as we know it, and environments that once contained rivers and lakes may have provided conditions suitable for microorganisms. Sedimentary rocks formed in such settings can also preserve traces of biological activity over long periods.
The collected specimen is approximately the size of a piece of chalk. Its most intriguing characteristic is a pattern of small spots resembling the markings found on a leopard’s coat. Similar features, known as reaction fronts or reduction spots, can form in terrestrial sediments when microorganisms interact with organic material.
Adrian Broz, a researcher at Purdue University and member of the Perseverance science team, notes that the sample stands out as a highly encouraging prospect for a possible biosignature. While this classification indicates that a characteristic might be linked to life, it does not confirm a biological genesis.
Furthermore, the adjacent mudstone exhibits several comparable traces, heightening scientific curiosity regarding the depositional setting of the stratum. Even so, investigators still need to ascertain if these configurations stem from biological activity or from abiotic chemical interactions.
Why scientists need the sample on Earth
Perseverance carries scientific instruments capable of examining Martian rocks, identifying minerals and gathering information about their chemical composition. These observations help researchers understand the geological history of the planet and select samples that deserve closer investigation.
However, the rover was designed primarily to study its surroundings and collect material for eventual return to Earth. Its onboard equipment cannot reproduce the full range of analyses available in specialized laboratories.
Briony Horgan, a professor of Earth, atmospheric and planetary sciences at Purdue University alongside being a member of the Perseverance team, has emphasized that researchers will not be able to reach definitive conclusions regarding potential biosignatures unless the specimens are analyzed directly on Earth.
Laboratories could subject the material to multiple complementary tests, allowing scientists to investigate its mineral structure, organic compounds and microscopic characteristics in greater detail. Using different analytical techniques would help establish whether the unusual patterns are consistent with biological activity or can be explained by geological processes.
The distinction is essential because a chemical signature that resembles one associated with life is not necessarily biological. Researchers must eliminate alternative explanations before claiming that extraterrestrial organisms once existed.
A well-known precedent illustrates the difficulty. The Martian meteorite Allan Hills 84001, discovered in Antarctica in 1984, attracted considerable attention after scientists proposed that some of its features might represent remnants of ancient life. Subsequent research showed that nonbiological processes could produce structures and chemical signatures that had initially appeared promising.
That encounter highlighted the necessity of exercising care when analyzing potential biosignatures. Even equipped with robust laboratory facilities, establishing whether a rock harbors traces of prehistoric microorganisms can prove to be an extraordinarily intricate challenge.
NASA’s sample-return mission faces an uncertain future
The original Mars Sample Return program was jointly conceived by NASA and the European Space Agency to bring specimens gathered by Perseverance back to Earth. Its complex blueprint featured multiple spacecraft, robotic mechanisms, and a series of procedures that would have demanded meticulous synchronization.
The initial concept, presented in 2020, envisioned sending a lander to Mars with a rover capable of retrieving samples and a rocket designed to launch them from the planet’s surface. A spacecraft in Martian orbit would then capture a container holding the material and carry it toward Earth, where another system would deliver it safely.
Over time, the design underwent several modifications. By the year 2022, NASA had contemplated instructing Perseverance to drop off its gathered samples straight to a lander fitted with a Mars Ascent Vehicle. Additionally, a pair of compact helicopters was integrated into the updated blueprint as a secondary contingency for retrieving samples should the rover fail to arrive at the targeted landing area.
Despite these adjustments, independent assessments identified growing technical complexity and escalating expenses. The estimated cost eventually reached as much as US$11 billion, while the projected return date shifted to 2040.
Financial pressures and concerns about the mission’s feasibility led NASA to reconsider the program in 2024. In January 2025, the agency identified alternative approaches involving commercial partnerships and technologies already used in previous Mars missions. However, its fiscal year 2026 budget request stated that the existing program would be terminated because the available designs remained unaffordable.
NASA has not abandoned the scientific objective of retrieving Martian material. In a statement shared with CNN in July, the agency said it was exploring potentially simpler and less expensive alternatives, including contributions from commercial companies and international partners. NASA administrator Jared Isaacman has also expressed interest in bringing the samples back, although a definitive implementation plan has not been announced.
Perseverance has already collected 33 tubes containing rock, dust and atmospheric material. Ten samples have been deposited at a designated storage location on Mars, creating an additional opportunity for a future mission to retrieve them.
China could become the first country to return samples from Mars
While NASA reassesses its strategy, China is developing its own mission to collect Martian material and transport it to Earth. Known as Tianwen-3, the project is expected to launch in 2028, with the goal of returning samples around 2031.
The Chinese mission draws on experience from previous planetary exploration projects, including Chang’e-6, which successfully returned the first samples collected from the Moon’s far side in 2024.
According to plans described by the mission team, Tianwen-3 would involve two launches. One would carry a lander, an ascent vehicle and a helicopter to Mars, while the other would transport an orbiter and a return vehicle. The lander is designed to drill as deep as 2 meters beneath the Martian surface, where material may be better protected from environmental conditions that can alter samples over time.
Researchers are assessing prospective landing locations according to their geological properties alongside the probability that they safeguard traces of prehistoric water or microbial life. The scheduled analyses entail looking for iron oxides capable of preserving microscopic formations as well as clay-dominant substances able to hold onto ancient organic compounds.
The exact scientific return of the mission will be dictated by the ultimate touchdown site, the specimens retrieved, and the subsequent laboratory tests following its homecoming. Consequently, the collected samples might well complement, instead of duplicate, the ones acquired by Perseverance.
If China succeeds before the United States, it could achieve a major milestone in planetary exploration. Beyond the geopolitical implications, the mission would provide researchers with valuable material for investigating Mars’s geological evolution and the conditions that may have existed when life first emerged on Earth.
Alternative plans offer hope for the Martian samples
Despite the termination of the initial NASA initiative, researchers and commercial collaborators keep investigating methods to recover the samples already gathered.
Lockheed Martin has developed a concept intended to return 30 of Perseverance’s samples for less than US$3 billion, with delivery targeted for no later than 2037. The proposal would use a relatively lightweight lander, a simplified Mars Ascent Vehicle and a compact system for delivering the samples to Earth.
The firm boasts a background in planetary undertakings, which encompasses NASA’s InSight initiative alongside the OSIRIS-REx asteroid sample-return voyage. Based on statements from Lockheed Martin, insights gained from such endeavors might streamline specific components of the suggested blueprint. Nonetheless, the proposal remains an unverified substitute venture, and its timeline will ultimately hinge upon subsequent maturation, budgetary allocations, and choices made by NASA.
Researchers remain interested in recovering the samples even if they ultimately contain no evidence of life. Their chemical composition could reveal how organic molecules form, how minerals interact with water and whether Mars once possessed conditions favorable to the emergence of living organisms.
The discoveries might additionally assist in solving a wider scientific conundrum: the reasons why organisms evolved on Earth, whereas existing data has yet to confirm if life ever arose on an adjacent planet sharing comparable environmental factors.
Sapphire Canyon therefore represents more than a promising rock. It is part of a collection that could transform understanding of Mars and the origins of life, provided scientists can examine it with the necessary precision.
For now, the sample remains sealed inside Perseverance, waiting for a mission capable of completing the journey to Earth. Whether NASA, a commercial partner or another space agency eventually retrieves it, the results could help determine whether life once existed beyond our planet—or whether the processes that produced life on Earth were far more unusual than scientists currently understand.
