NASA’s plan to collect rock samples on Mars and bring them back to Earth has been canceled – here’s what it means for scientific research.
The most ambitious project of modern American planetology is nearing its end. NASA’s plan to collect Martian rock samples and return them to Earth — the Mars Sample Return (MSR) program — has been canceled. This is confirmed by the compromise bill on federal spending for the current fiscal year, published by Congress, which implements the White House’s commitment to dismantling the program.
Although the text still needs to be approved by both houses and signed by the president, the message is clear: the Mars Sample Return is not a priority for the United States. A decision that leaves one of the most important scientific objectives of planetary exploration suspended and which, at least for now, condemns to abandonment the dozens of rock cores collected by the Perseverance rover in the Jezero crater.
Give up. “It’s deeply disappointing,” comments Victoria Hamilton, a planetary scientist at the Southwest Research Institute and president of NASA’s Mars Exploration Program Analysis Group. “When we hear that the United States wants to remain the dominant power in space, it is difficult to understand how anyone can give up something so ambitious.”
The Perseverance rover, which landed on Mars in 2021, was designed specifically for a future recovery mission: it collected selected samples, sealing them in test tubes that should have been picked up by a robotic vehicle and launched into Martian orbit. Without MSR, that work risks remaining unfinished.
The goal? Free up resources. Paradoxically, the cancellation of MSR could reopen the way to planetary missions that have been blocked for years. The compromise bill allocates $7.25 billion for NASA science: a 1% cut from the previous year, but much higher than the White House’s initial proposal, which called for a drastic reduction of the science budget. This saving could make it possible to relaunch already selected projects, such as two missions to Venus or to accelerate the development of a probe for Uranus, considered crucial for the study of icy giant planets and their satellites.
However, there is a glimmer of hope: MSR is not completely canceled. $110 million has been allocated for a new chapter called “Mars Future Missions”, intended to develop the program’s key technologies, such as complex landing and ascent systems in the thin Martian atmosphere. According to Jack Kiraly, director of government relations for the Planetary Society, this could allow NASA to “reset” the project in the future, if political and economic conditions allow.
Too expensive a project. For years, MSR has divided the scientific community. The widespread fear was that its growing cost — reaching $11 billion in 2024 — would end up absorbing an excessive share of NASA’s science budget, putting other missions at risk. Not surprisingly, the program survived multiple cancellation attempts, remaining alive only thanks to continuous revisions. The agency’s latest proposal, released in January 2025, reduced the estimated cost to about $7 billion, but even this figure proved unsustainable in a context of widespread overruns and limited resources.
The international consequences. The American decision also has consequences across the Atlantic. MSR was conceived as a joint project with the European Space Agency (ESA), which was supposed to provide the Earth Return Orbiter, the vehicle responsible for intercepting the sample container in Martian orbit and returning it to Earth.
ESA has already invested significant resources in the development of the vehicle and, in late 2025, hinted that it may convert it back into an autonomous Mars orbital observation mission. A choice which, if MSR were resumed in the future, could further increase costs if the European orbiter were no longer available.
Precious samples. In 2024, the Perseverance rover spotted what many researchers consider the most promising hint of past life on Mars. The sample, taken from an ancient river delta in Jezero Crater and named Cheyava Falls, contains mineral structures nicknamed “leopard spots,” similar to those associated with microbial activity on Earth.
Determining whether these are truly biosignatures is impossible without in-depth laboratory analysis. “A rock with a potential biosignature is there, ready to be studied, along with other samples that contain groundbreaking discoveries,” emphasizes Bethany Ehlmann, a planetary scientist at the University of Colorado at Boulder.
Scientific leadership. According to Philip Christensen, of Arizona State University, giving up MSR also means giving up ground on a geopolitical level. China, in fact, is developing its own program to return samples from Mars, with similar objectives. “The scientific return of the Mars Sample Return would have been extraordinary,” says Christensen, “and would have provided the scientific and engineering foundation for human exploration of the Red Planet.”
The uncertain future of Perseverance. Finally, a practical question remains: what will NASA do with Perseverance now? The rover is approaching five years of activity on Mars and has almost completed its set of test tubes.
«We need to know as soon as possible», concludes Hamilton, «if and how NASA intends to collaborate with the scientific community to define a plan that will allow, sooner or later, to bring these samples home». For now, Mars’ most precious rocks remain there, sealed and waiting.
