A leopard-spotted rock that could prove whether life ever existed beyond Earth is sitting in a tube on Mars. NASA’s Perseverance rover grabbed up the sample, called Sapphire Canyon, from rocky outcrops on the edges of the Neretva Vallis, a valley sculpted by rivers that once flowed into an ancient lake in Jezero Crater more than 3 billion years ago. The rover landed at the dried lakebed in February 2021 for expressly this purpose, hunting for rocks created or modified by water in the past, which would have had the best chance of preserving evidence of life. Members of the Perseverance science team have said the Sapphire Canyon sample, about the size of a chalk stick, is exactly the type of rock they hoped the rover would discover. “This is the first time I think we’ve found something that qualifies as a ‘potential biosignature’” on Mars, said Adrian Broz, a member of Perseverance’s science team and a postdoctoral researcher in the Planetary Surface Processes Lab at Purdue University in Indiana. “It’s currently sealed inside of Perseverance rover’s chassis, and it sits there quietly and awaits return to Earth.” But the sample might not make it to our planet, at least not anytime soon. The Mars Sample Return program, a joint venture by NASA and the European Space Agency to ferry the promising cache back to Earth, attracted intense scrutiny for its high price tag and complex design. After sinking billions of dollars into the endeavor, NASA paused and began reassessing the program in 2024 before canceling it entirely — with no clear alternative in sight. “While Perseverance’s samples remain safely stored on Mars, NASA is exploring a range of potential return options that could offer simpler and more affordable approaches than the original Mars Sample Return plan, including possible commercial or international contributions,” the agency said in a statement shared with CNN in July. NASA’s leaders still haven’t revealed a path forward. And while the discovery of the Sapphire Canyon sample is building a strong case for the existence of ancient microbial life on Mars, there’s only so much scientists can learn from afar, said Dr. Briony Horgan, professor of Earth, atmospheric and planetary sciences at Purdue University. The rover, which cost NASA about US$2.4 billion to build and launch, doesn’t have the instrument suite to answer such lofty questions by itself on the red planet. “We can keep doing these studies and coming up with these hints, but we’re never going to know for sure until we get those samples back,” said Horgan, also a coinvestigator and planner on the Perseverance team. “These samples are our best current chance for really understanding is life abundant and common, or is Earth truly unique?” Now, it’s possible one of NASA’s biggest competitors in the new space race will be the first to achieve Mars sample retrieval: China is looking to pick up its own souvenir from the red planet in 2031, and it has taken steps to ensure success by designing a mission that’s similar to one it pulled off two years ago. But the rocks returned by the country’s Tianwen-3 mission, expected to launch in 2028, could look very different — and perhaps offer different insights — from Perseverance’s samples, depending on how plans evolve. ‘Scientific holy grail’ Scientists consider Sapphire Canyon such a promising find because of its spotted appearance. On Earth, the tiny dots, called reaction fronts or reduction spots, form in soils and sediments due to the presence of microbial activity. “When there’s organic matter that’s lodged in sediment or soil that’s buried and microbes start to digest some of that organic matter, they form these bleached halos and spots that are quite resemblant to the ones that Perseverance found in this ancient river valley,” said Broz, coauthor of a study about the rock sample published in September 2025. Perseverance drilled the Sapphire Canyon sample from an arrowhead-shaped rock called Cheyava Falls in July 2024. The mudstones surrounding the rock were also covered in hundreds of thousands of promising reduction spots potentially made by ancient microscopic life. Still, returning the samples to Earth is the only way to determine whether these distinctive features were formed by the presence of life, or abiotically — through chemical or geological processes that did not require life, Broz said. It’s a lesson planetary scientists learned from studying the famed Allan Hills 84001 Martian meteorite, uncovered in the Antarctic in 1984 and originally thought to contain the remnants of ancient life. Multiple groups of scientists analyzed samples from the meteorite, discovering that nonbiological, geological processes left behind signatures that could be misinterpreted as organic carbon compounds attributed to life. “Even when you have all the labs all over the world looking at a rock that has putative evidence of ancient life, it is a really difficult thing to do, and so you want to just be able to apply every technique you can think of in all the best labs,” said Ashwin Vasavada, project scientist for the Curiosity rover at NASA’s Jet Propulsion Laboratory in Pasadena, California. The rover’s onboard tools can offer some data, but they weren’t designed to do the kind of analysis necessary to make definitive answers because that wasn’t part of the original plan. “The science instruments had been selected with the assumption that they would be doing reconnaissance for sample selection and providing the geologic context on Mars for samples that were always expected to be returned to Earth,” said Dr. Melissa Rice, a professor of planetary science at Western Washington University who has worked on NASA rover missions for over two decades. The first entry in NASA’s budget request to Congress for initial studies of a Mars sample return program occurred in the fiscal year 1978, according to Casey Dreier, chief of space policy at The Planetary Society. The request was made on the heels of the agency’s Viking missions to Mars, considered NASA’s first attempt to search for evidence of life on the red planet. “It tells you how long it has remained this kind of scientific holy grail for Mars,” Dreier said. A 2003 survey identifying top scientific objectives for future space missions — and several subsequent reports — highlighted retrieving red planet samples as a key priority, which led to Mars Sample Return becoming intertwined with the Perseverance rover’s mission. The two projects were developed hand in hand. A complicated path The original concept for Mars Sample Return, shared in 2020, included a succession of multiple missions launching from Earth to Mars: a lander containing a Mars fetch rover to collect the samples and an ascent vehicle to return the samples to Earth by 2031 at the earliest. The ascent vehicle was intended to shoot out a football-size container holding the samples that would be captured by a separately launched ESA spacecraft orbiting Mars. Then, the ESA orbiter would head back to Earth, transferring the sample container into yet another vehicle that could deploy from the orbiter and safely land the samples on our planet. By 2022, the plan shifted: Perseverance would deliver the sample suite to the Mars Ascent Vehicle that would launch on a return journey. The lander would carry two small recovery helicopters, which could grab samples from the rover if Perseverance wasn’t in good enough condition to make the drive to a landing site. This nudged the return date to 2033. As things progressed, assessments from independent review boards pointed out how unwieldy and complex the retrieval process had become. The program’s budget ballooned to an eye-popping maximum of US$11 billion and the estimated return date for the samples pushed to 2040. NASA also faced budget cuts for the 2024 and 2025 fiscal years, and the excessive costs of the mission led to waning political support for the program. The agency put out a call for cheaper, quicker and less complex proposals and, in January 2025, identified two strategies that relied on commercial partnerships or leaned on previously used Mars landing technology so as to not reinvent the wheel. That assessment came out just weeks before President Donald Trump took office and began the search for a new NASA administrator. The next sample return update, revealed with NASA’s fiscal year 2026 budget request, was an abrupt blow: “NASA plans to terminate the Mars Sample Return Program given that current architecture options remain unaffordable. It is anticipated that future missions to Mars will return samples for study on Earth.” The agency’s 2027 budget request didn’t mention the program at all. NASA spent about US$2.5 billion on the Mars Sample Return through its cancellation, Dreier said. However, NASA administrator Jared Isaacman has mentioned that he’s interested in getting Perseverance’s samples delivered to Earth. “As I’ve said many times, I think retrieving the samples from Mars can lead to the most significant scientific breakthrough in human history,” Isaacman said at a news conference on August 30 after the successful launch of the Nancy Grace Roman Space Telescope. “There’s no question we’re going to go get samples, whether it’s robotic or whether it’s astronauts picking it up will be the question, and certainly the time frame associated with it.” Speaking at the All-In Summit in September, Isaacman blamed his predecessors for the program’s failures, noting “the prior administration canceled the Mars Sample Return mission that was on track to cost more than an aircraft carrier.” While the finger-pointing about the fate of the original program appears to continue, no additional details about next steps have emerged. China’s challenge China’s plan to fetch Mars samples is also complex, though arguably less so than NASA’s original design. Called Tianwen-3, the approach China is using draws on the success of Chang’e-6, a 2024 mission that retrieved the first samples from the moon’s far side. Tianwen-3 will include two launches: one for a lander, ascent vehicle and helicopter, and another for an orbiter and return vehicle to shuttle the samples to Earth, according to a study published by the mission team in 2025. The lander is equipped with a drill that can reach 2 meters (6.5 feet) beneath the Martian surface, the ideal place to search for signs of past or present life. The helicopter can also gather rock samples. Mission scientists plan for the lander to operate on Mars’ surface for about 70 days during sample collection, according to Yiliang Li, a core member of Tianwen-3’s science team who is aiding in the selection of landing sites. The Tianwen-3 team is narrowing down a list of 86 potential landing sites to identify regions where liquid water once existed on Mars, mineral-enriched regions and areas where ancient microbial activity could still be preserved, according to a 2024 study. Jezero Crater does not appear to be on the list. Ideally, the mission will retrieve two types of samples from ancient lake beds, said Li, a coauthor on both studies. The team is aiming to find one sample with iron oxides, which might have preserved cell shapes for billions of years, and a second sample that contains thick aquatic clays because they could contain ancient organic molecules created by living organisms, said Li, who is also a professor of astrobiology in the department of Earth and planetary sciences at the University of Hong Kong. Zengqian Hou, Tianwen-3’s chief scientist and economic geologist of the Chinese Academy of Sciences, announced in September at the International Deep Space Exploration Conference that engineers are currently building a prototype of Tianwen-3. China also plans to build a planetary protection laboratory to house the samples, Hou said during the announcement. In recent years, NASA has focused increasingly on America-first messaging to position the US as leading the charge on marking milestones in space, including of beating China at being the first to land humans on Mars. A sample return win for China would certainly undermine that message. “American exceptionalism is being challenged in the high ground of space,” NASA Administrator Isaacman said while testifying on the 2027 NASA budget proposal in April. “To win, we cannot establish programs designed to be ‘too big to fail,’ but at the same time ‘too costly to succeed.’ Nor should it be throwing more money at the problem, but rather fixing the problems, concentrating resources on the mission and delivering outcomes.” Even as it ramps up the “space race” rhetoric in its efforts to return humans to the moon, the agency has made no mention of the fact that China may be the first to retrieve Martian samples — despite NASA already having a leg up with collected samples that just need to hitch a ride to Earth. “It’s remarkable that the US has advocated its leadership in this area of space exploration and just handed China the win in that one sector of the space race,” Rice said. Glimmer of hope Scientists remain hopeful that the Perseverance samples will be returned in some way, Horgan said. The ongoing work of industry partners is part of what’s keeping researchers optimistic. Lockheed Martin, for example, has worked with NASA on Mars missions and other sample return efforts in the past, which enabled the company to develop a streamlined concept to pick up the abandoned Perseverance samples, said Whitley Poyser, director of Lockheed Martin’s exploration mission area. The proposal included a fixed-price mission under US$3 billion to return 30 of the rover’s samples to Earth no later than 2037. The concept revolved around using a lightweight Mars Ascent Vehicle, a small lander inspired by Lockheed Martin’s involvement in the InSight mission to Mars, and a compact Earth delivery system derived from lessons the company learned by assisting with the OSIRIS-Rex asteroid sample return mission, Poyser said. The company remains committed to their plan for retrieving samples from Mars and is prepared if the opportunity comes their way, she said. “The big area from a technical perspective that needs to mature is Mars ascent, especially if we are going to send someone there and send them back,” Poyser said. “We want to know how it’s going to work. All of those technologies are critical and they can be demonstrated through Mars Sample Return.” Even if the samples don’t contain signs of life, scientists say that knowledge could present intriguing possibilities, including the idea the spots may have been the work of prebiotic chemistry — the soup of elements, metals and organic carbon that could have formed a cell or living entity but didn’t reach its full potential. And if it turns out that life never existed on Mars, one of our planet’s closest neighbors, then why did it arise on Earth and not a world with similar conditions during the same time frame? Martian samples could tell the tale in a way that Earth’s rocks, shaped and lost over time due to erosion and other processes, can’t — and it’s up to the scientific community to share that message, Rice said. “I think there’s going to be a lot of advocacy for years to come, making sure that the general public is aware of how close we are to answering those big questions,” she said. “The rocks are there, they’re in their tubes, they’re ready. All we got to do is go get them.”
