NASA and ESA's Mars Sample Return mission has been canceled

A compromise spending bill released by the US Congress on 5 January 2026 has effectively killed NASA's Mars Sample Return (MSR) program — the mission that was to ferry rock cores collected by the Perseverance rover back to Earth. The text of the bill is explicit: “The agreement does not support the existing Mars Sample Return program.” It still needs approval from both chambers and the president, but the decision is already read as the program’s end.

What Congress decided

Congress did not cut the program entirely. It shifted $110 million into a new “Mars Future Missions” program that will continue work on technologies MSR had been developing, including systems for landing spacecraft in the thin martian atmosphere. Jack Kiraly of the Planetary Society says the money could let NASA reset the effort later.

The cost problem

MSR had long divided planetary scientists as its price tag grew. In 2024 the cost estimate rose to $11 billion, and Congress repeatedly threatened cancellation while NASA reworked its plans. The agency's final proposal, released in January 2025, would have brought the cost back down to $7 billion, but even that was judged too high. The compromise bill budgets $7.25 billion for NASA science — a 1% cut, yet far more than the administration's proposal to halve it — which could free funding for stalled projects such as two chosen Venus missions and a Uranus probe.

ESA's role and what is lost

MSR was a joint project with the European Space Agency, which was to supply the Earth Return Orbiter: a spacecraft that would catch the container of rock samples launched off the martian surface and carry them to Earth. ESA has already done much of the work on it, and late last year it indicated the project could be reworked into a standalone mission to study martian geology from orbit.

Perseverance, exploring Jezero Crater since 2021, has collected several dozen rock cores. In 2024 it drilled the Cheyava Falls sample from an ancient riverbed; the rock contains mineral deposits known as “leopard spots” that resemble traces left by microbes on Earth. “A rock with a potential biosignature is awaiting return now, and other rocks hold breakthrough discoveries,” says Bethany Ehlmann of the University of Colorado Boulder. Philip Christensen of Arizona State University says abandoning the effort signals a loss of US leadership, especially as China builds its own Mars sample-return program: “The science return from MSR would be exceptional and would provide the scientific and engineering foundation for sending humans to Mars.” Victoria Hamilton of the Southwest Research Institute, who chairs NASA's Mars Exploration Program Analysis Group, calls the decision “deeply disappointing” and says the community wants to hear soon how NASA plans to use the rover's remaining time.