For more than four years, NASA’s Perseverance Mars rover has been on the prowl within Jezero Crater, a site on the Red Planet that eons ago harbored a sprawling river delta, a large, deep lake and—just maybe—ancient Martian life. Since its touchdown in February 2021, the car-sized, nuclear-powered robot has traveled far and wide across this otherworldly terrain, dutifully gathering samples of rock and soil. Protected in hermetically sealed metal tubes, these specimens are meant for future retrieval and delivery back to Earth, where close-up inspection in state-of-the-art labs might at last provide the first compelling evidence of life beyond Earth.
This cooperative program between NASA and the European Space Agency (ESA) is known as Mars Sample Return (MSR) and has been generations in the making. It’s the culmination of decades of planning by planetary scientists and many billions of dollars in government spending—the crowning achievement of Mars-focused interplanetary exploration efforts that began more than a half-century ago and still endure today.
Unless, that is, the Trump administration gets its way: on May 2 the White House’s Office of Management and Budget (OMB) dropped a budgetary bombshell, proposing to cut NASA’s top-line funding by a quarter, slash the space agency’s science budget by nearly half and entirely eliminate MSR. The cancellation is justified, the OMB document claims, because MSR is “grossly overbudget” and its goals of sample return will instead “be achieved by human missions to Mars.”
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The news apparently came as a surprise to high-ranking officials. Addressing a meeting of NASA’s Mars Exploration Program Analysis Group (MEPAG) just two days before the announcement, the space agency’s Donya Douglas-Bradshaw, director for the MSR program, offered an upbeat status report. MSR “will be the first round-trip mission to another planet,” she said, “and will be the first time that we actually launch from another planet.”
In her remarks, Douglas-Bradshaw did acknowledge the program’s growing pains. Over the years, multiple independent reviews of the MSR project have flagged its swelling price tag and slipping schedule. One recent review estimated that it would cost about $11 billion and return samples to Earth in 2040—a price too high and a time frame too slow to be acceptable, Douglas-Bradshaw said.
Last year, triggered by those figures, yet another review envisioned a streamlined version of MSR that could deliver samples as early as 2035 for a cost of some $8 billion. This replan called for NASA to simultaneously study two options for bringing Perseverance’s precious tubes back to Earth. Both were meant to rein in costs and accelerate the schedule through a combination of private-sector innovation and leveraging preexisting “heritage” hardware. The space agency anticipated selecting between the two options and finalizing MSR’s replan before the end of 2026, Douglas-Bradshaw told the gathered MEPAG scientists.
“Nonsense on Several Levels”
MSR’s proposed cancellation would overturn decades of arduous planning and deliberate investments while also diminishing U.S. space leadership on the global stage, says MEPAG chair Victoria Hamilton, a space scientist at the Southwest Research Institute. The project, she notes, was ranked as the highest priority of U.S. planetary science in two consecutive Decadal Surveys—authoritative communal reports that historically give Congress and federal agencies recommendations for future activities. And without MSR other nations could seize the opportunity to pull off sample-return missions of their own before the U.S. and its allies could recover.
Of the $1.8 trillion budgeted for federal discretionary spending in fiscal year 2024, $7.8 billion went to NASA’s science efforts—less than half a percent of the total. Yet “with that investment, NASA’s robotic exploration programs are the greatest in the world and spark the imagination of America’s future scientists and engineers,” Hamilton says. “It’s crucially important that NASA maintain U.S. leadership in deep space by pursuing the ambitious goals outlined in our Decadal Surveys, lest we cede leadership to other nations, such as China.”
And while it’s true that crewed missions to Mars have long been NASA’s polestar, endorsed by both Trump administrations as well as that of former president Joe Biden, many experts lambast the notion that U.S. astronauts could return Perseverance’s samples anytime soon.
“Let’s get real. My reaction to the ‘astronauts will do sample return’ is: When?! It’s nonsense on several levels,” says Stanford University planetary scientist Scott Hubbard, who served as NASA’s inaugural Mars program director (or “Mars Czar”). “I know of no credible ‘humans to Mars’ scenario that is earlier than 2039 or 2040.”
Meanwhile, Hubbard says, China has announced plans for a more basic Mars sampling endeavor around 2030 that would likely entail a lander simply snatching nearby material from some easily accessible spot on the surface. That would be in stark contrast to MSR’s more methodical approach, which is designed to deliver many samples sourced from a wide range of terrain and carefully curated to be of maximal scientific value—that is, material thought most likely to harbor evidence of past or even present Mars life. “Even if it is only a ‘grab’ sample, [China] can rightly claim [it] beat NASA and the U.S.,” Hubbard says.
The true value of MSR is in the high quality of its samples, says Casey Dreier, chief of space policy at the Planetary Society, a nonprofit organization that advocates for space science and exploration. “Random rocks will almost certainly not answer the big questions that MSR is designed to answer, such as the age of the Martian surface, the possible presence of biosignatures and the nature of Mars’ ancient atmosphere. That’s the weakness in China’s ‘grab-and-go’ approach.”
Furthermore, he says, the Trump administration’s claims that the MSR mission is unaffordable—yet also somehow readily replaced by crewed exploration—are dubious at best. Any remotely realistic plan for a crewed Mars mission would be far more expensive than MSR, for one thing. For another, the very act of landing humans on Mars could undermine the deep astrobiological questions that justify the sampling effort in the first place. Most experts argue that astronauts would inevitably import some Earthly microbes to the Martian surface, potentially compromising the integrity of supposedly pristine samples as well as that of the planet itself.
None of which means that humans should be forever forbidden from Mars or that astronauts could play no role whatsoever in sample return, Dreier hastens to add. “There are a number of novel approaches for MSR that should still be considered, including a tighter coupling with future human exploration of Mars. It is premature to cancel it as this stage and certainly premature to do so before a confirmed NASA administrator helms the agency and is able to make a fuller assessment of the project,” he concludes.
“Mystifying and Infuriating”
Indeed, President Trump’s nominee for running NASA, entrepreneur and two-time private space traveler Jared Isaacman, has yet to officially weigh in on this new MSR development. At his most recent Congressional appearance on April 9— before the OMB’s bombshell sent shockwaves through all of U.S. space science—he offered sunny testimony about NASA’s bright future.
On April 30, the Senate committee that oversees NASA and other federal science agencies gave Isaacman its nod to advance to a formal confirmation vote in the full chamber. That confirmation could be days, weeks or months in the making, however—and it’s uncertain whether Isaacman has sufficient political capital to oppose or even question any of the Trump administration’s budget-snipping edicts.
Amanda Hendrix, director and chief executive officer of the Planetary Science Institute, worries that such potential gaps in political leadership could prove ruinous well beyond the “mystifying and infuriating” possible cancellation of MSR.
“It’s as if [the Trump administration] want the U.S. to cede leadership in space exploration and science,” she says. “These proposed cuts are so bad that we cannot wait for Congress to go through the normal appropriations process. Congress needs to push back hard now.”
To understand how shocking the prospect of MSR’s downfall really is, consider that even some of the endeavor’s historic opponents are now speaking up in its defense—albeit with caveats. Robert Zubrin, an aerospace engineer and founder of the Mars Society, has long been a fierce critic of MSR; he has argued that NASA’s Mars exploration program would be better served by a more numerous and diverse mix of small- and medium-sized missions. Even so, he can’t bring himself to support the proposed cancellation.
“While you can raise objections to the MSR mission, that money should be rescheduled to run a Mars exploration program with more rovers, more robotic helicopters, orbiters and life-detection experiments,” Zubrin says. “Instead [the Trump administration] just cancels the MSR and basically shuts down the Mars exploration program. And that’s wrong.”
“Work in Progress”
As uncertainty and confusion cloud the outlook for MSR and federally funded science as a whole, longstanding international partners of the U.S. see little choice but to project an outward sense of calm. Look, for instance, to the statement issued on May 5 by ESA’s director general Josef Aschbacher that carefully emphasizes the importance of U.S.-European cooperation in space activities.
Via ESA, Europe’s main contribution to MSR is an Earth Return Orbiter (ERO) that would snare and stow a surface-launched sample-return capsule in Mars orbit, then ferry it back toward our planet. In October 2020 ESA signed a €491-million contract with Airbus to design and build ERO; the spacecraft is now in the closing phases of its development, which includes integration and testing of its various components in preparation for launch. If MSR is mothballed, ERO could become a nearly half-billion-euro boondoggle for ESA, which has an annual budget that’s only a small fraction of NASA’s.
Aschbacher did not directly address ERO or MSR in his statement but did note that a more detailed version of the Trump administration’s budget request is expected in late May or early June.
“The Budget Request release marks the beginning of the appropriation process in US Congress culminating in the President’s signature of the budget bill passed by the House and the Senate,” Aschbacher said. “Thus it should be kept in mind that this is still very much a work in progress.” Based on the outcome of that process and other further developments, the space agency will hold meetings later this year to plot “potential actions and alternative scenarios for impacted ESA programmes and related European industry.”
ESA, Aschbacher pointedly added, “has strong partnerships with space agencies from around the globe and is committed to not only being a reliable partner, but a strong and desirable partner.”
Perhaps not by coincidence, two days after his statement, Aschbacher was in New Delhi, where he signed a joint statement of intent between ESA and the Indian Space Research Organization (ISRO) to cooperate on future crewed missions to low-Earth orbit and to the moon. In spite of ESA’s measured “wait-and-see” response to the political chaos now engulfing the U.S., Europe’s embrace of new, non-American partners for space exploration signals that an old adage still rings true: the future waits for no one.
