In the Martian lowlands, one rocky crater is dotted with small holes, winding from the floor to the rim like breadcrumbs. Their clean and cylindrical appearance is distinctly unnatural, suggesting the work of aliens—which it is. For three years, a robot from Earth has been collecting samples of rock and soil into six-inch-long tubes, whirring and crackling on the otherwise quiet planet. The robot, a rover named Perseverance, has deposited some of the samples on the Martian surface in sealed tubes. The others, about two dozen so far, remain stored inside the rover's belly.

Perseverance will stay on Mars forever, but the majority of its carefully packaged samples are meant to return to Earth. The Mars Sample Return mission, known as MSR for short, is one of the boldest undertakings in NASA history, as consequential as it is complicated. The endeavor, which involves sending an extra spacecraft to the red planet to retrieve the samples, serves as a precursor to getting future astronauts home from Mars. It’s a test of whether the United States can keep up with China’s space program, which is scheduled to return its own Mars samples in the 2030s. It could uncover new information about our planetary neighbor’s history, and reveal a picture of the cosmic wilderness that was the early solar system. Some scientists hope the dusty fragments will contain tiny fossilized microbes that would prove life once existed on Mars. Those tiny life forms will have been dead for who knows how long—but still would be evidence of a second genesis in our own backyard.  

If, that is, the samples ever make it back to Earth. NASA officials recently announced that the sample-return effort has become too expensive and fallen worryingly behind schedule. The latest estimated cost of as much as $11 billion is nearly double what experts initially predicted, and the way things are going, the samples won't arrive home until 2040, seven years later than expected. At a press conference last month, NASA chief Bill Nelson repeatedly called the state of the Mars Sample Return mission "unacceptable," a striking chastisement of his own agency, considering that MSR is an in-house effort. Officials have put out a call—to NASA’s own ranks and to private space companies—for “quicker and cheaper” plans that don’t require “huge technological leaps” to bring the samples home.

[Read: Scientists really, really want a piece of Mars]

NASA officials say that they remain committed to the return effort, but researchers—including the agency’s collaborators who work on the project—are concerned. “The path forward is not clear,” Aileen Yingst, a geologist at the Planetary Science Institute who works on the Perseverance mission, told me. Scientists who study Mars are worried that the mission will be downsized. Scientists who don’t study Mars—and a few who do—are frustrated, because MSR consumes so much of NASA’s budget. Scientists can’t imagine NASA giving up on the mission entirely, but the debacle has even prompted some whispered jokes about China coming along and claiming the tubes on the surface before NASA can fly them home. Last year, an independent review ordered by NASA ominously warned that “by abandoning return of Mars samples to other nations, the U.S. abandons the preeminent role that [President John F. Kennedy] ascribed to the scientific exploration of space.”

If and when the MSR tubes come home, their contents could dramatically shift our understanding of Mars. The first NASA spacecraft to land on Mars, in 1976, carried instruments designed to examine Martian soil for evidence of tiny, metabolizing life forms but didn’t find anything conclusive. Some bits of Martian rock, ejected by colliding asteroids, have made it to Earth as meteorites. (And scientists have tried to find proof of life in these, too). But such fragments arrive scorched by atmospheric reentry, their composition altered and contaminated from the journey. Pristine samples are far more tantalizing.

MSR would deliver Martian dirt straight from an area that scientists believe holds a promising chance at containing signs of life from 3.5 billion years ago. The Perseverance rover is exploring the shores of what scientists believe was once a lake, at a crater called Jezero, where the sedimentary rock may bear signs of a once-habitable world, or preserved life itself. The samples might also offer hints about Earth’s origin story. The rocks that existed here 4 billion years ago, when the solar system was just getting started, have since been crushed, melted, and eroded away. But Mars, a world lacking plate tectonics and serious weather, still bears rocks from the time of its very formation.

[Read: The most overhyped planet in the galaxy]

The promise of such samples has been a top research priority for planetary scientists for over a decade. The original plan to do so, devised by NASA’s Jet Propulsion Laboratory (JPL), is accordingly ambitious, involving several different spacecraft to retrieve the capsules, launch them into Martian orbit, and fly them back to Earth. No astronauts are involved, but Mars scientists have likened the mission choreography to the Apollo program in terms of complexity.

That plan was apparently destined to unravel from the start. NASA’s independent review found that MSR had “unrealistic budget and schedule expectations from the beginning" and was "organized under an unwieldy structure," with "unclear roles, accountability, and authority.” Technically ambitious missions always cost more, and MSR is arguably one of the most complicated that NASA has ever undertaken. But the scientists who help NASA set exploration priorities have no control over the budgets of the resulting programs—Congress does.

Last summer, some congressional appropriators briefly threatened the entire MSR effort with cancellation. This February, facing uncertainty over the money that Congress would allocate for MSR in the next fiscal year, the JPL laid off more than 500 employees. (Congress has since allocated a fraction of what NASA spent on the mission last year.) Thanks to budget concerns, NASA has delayed the launch of a telescope that would monitor potentially hazardous asteroids near Earth, and put on hold a proposed mission to study Earth’s atmosphere and magnetic field.

Some scientists fear that MSR will draw resources away from other potential projects to search for life in places that they now believe to be far more promising than Mars. The search for alien life in the solar system has long been guided by water, and in the 1990s, when NASA kicked off a golden age of Mars missions, the red planet’s ice regions seemed appealing. But in the years since, other celestial bodies have become more compelling. A moon of Saturn, Titan, is the only body in the solar system besides Earth that has bodies of liquid on its surface, even if that liquid is methane. Two moons of Jupiter, Europa and Enceladus, are likely icy worlds with subsurface oceans; on the latter, cracks in the ice release plumes of salty water, hinting at something like deep-sea hydrothermal activity on Earth. NASA is launching an orbiting mission to Europa later this year, and the latest survey of planetary scientists advised NASA to start working on another to Enceladus. “If I could go anywhere, I would go to Enceladus,” Brook Nunn, an astrobiologist at the University of Washington, told me.

[Read: Mars’s soundscape is strangely beautiful]

Even some Mars scientists believe that Mars is no longer the top candidate. Darby Dyar, a planetary geologist at Mount Holyoke College, has spent decades studying Mars. “If anybody should be enthusiastic about the returned samples, it’s me, and I am,” she told me. But now she works on a NASA mission to Venus, a planet that might rival Mars as a candidate for extraterrestrial life, and she says she wouldn’t prioritize MSR over her current research.

For scientists who support Mars exploration, MSR is a problem, siphoning funds away from other efforts to study it. “There’s so many aspects to studying a planet that do not involve analyzing small amounts of rocks in the lab,” says Catherine Neish, a planetary scientist at Western University, in Canada, who’s working on an international mission to map the ice deposits on Mars’s polar regions. NASA pulled its financial support from that project in 2022, citing MSR’s cost as part of its motivation. Planetary scientists have recommended prioritizing a mission to drill deep into the ice at the Martian poles, far from Perseverance’s domain, where conditions could be just comfortable enough to support small life forms now.

NASA is well aware of the all-consuming nature of MSR. As the mission is redrawn, officials have said they are even willing to consider proposals that would bring home just 10 sample tubes, one-third of the amount initially planned. Lindsay Hays, a program scientist at NASA’s planetary-science division, told me that NASA will seek input from the science community about which sample tubes to return. “NASA has a responsibility to use taxpayer funds in the most effective and efficient way possible,” she said. “But it’s also part of our mandate to the nation to do things that have never been done before.”

[Read: Too much of a good thing at NASA]

Most planetary scientists aren’t happy with a potentially scaled-back approach either. “You’ve decimated the science, because now you’re not going to get the diversity that you could have if we brought back the full suite of samples,” Phil Christensen, a geologist at Arizona State University who co-chaired the community’s latest decadal survey, told me.

A badly delayed sample-return mission would fracture NASA’s grand vision for its Martian future. By the 2040s, NASA intends to be focused not on the red planet’s soil, but on sending astronauts there and, crucially, bringing them back. That operation relies on having successfully practiced launching off from Mars, which NASA hasn’t yet managed with MSR. Instead, the agency is back at the drawing board, hoping to find a way out of an $11 billion pit. Officials expect to finish reviewing new proposals and come to a decision on the mission’s future in the fall. Meanwhile, Perseverance chugs along, excavating the mythical oasis of Jezero Crater with each curated tube.

The war for a free society will not be won from an ivory tower in Washington or Brussels, but only through the action taken by local leaders on the ground, Brad Lips writes.