In early June NASA engineers put the finishing touches on a technological marvel years in the making: a golf cart-sized rover designed to drive into the cold and darkness near the moon’s south pole, on the hunt for water ice. If successful, the $450-million rover—called the Volatiles Investigating Polar Exploration Rover (VIPER)—would at last provide crucial “ground truth” for decades of speculation about where water is on the moon, supercharging both lunar science and a new international space race to harvest ice for air, water and fuel.
But now that fully assembled rover may be undone. Facing brutal budgetary shortfalls, NASA officials suddenly announced VIPER’s cancellation last Wednesday, sparking disappointment and fury among lunar scientists across the U.S.
“I was shocked and dismayed.... This is maybe the most important mission for developing cislunar space that NASA has ever designed,” says planetary scientist Phil Metzger of the University of Central Florida.
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Barring a Hail Mary pass of VIPER to another country’s space agency or a private U.S. company, the revolutionary rover will be dismembered for parts within weeks. Adding insult to injury, having already purchased VIPER’s nonrefundable ride to the lunar surface for more than $300 million, NASA intends to fly a dummy “mass simulator” in its place. To avoid more expenditures and delays, NASA has rejected the idea of sending any of the rover’s science instruments aboard.
Taken together, if VIPER fails to fly, the agency will have spent about $800 million to send literal deadweight to the moon instead.
In the Dark on Lunar Ice
For more than two decades data collected from lunar orbit have hinted that water ice abounds in soil near the moon’s north and south poles, especially in the sunless, frigid depths of craters there. But so far, no mission has visited these high latitudes to directly, thoroughly check those observations. How deep does the ice go? How does it vary across the surface? Does the moon’s water merely consist of individual molecules clinging to soil grains, or are there slabs of ice lurking in the polar shadows?
VIPER was built to answer these questions. The 950-pound rover could navigate treacherous lunar terrain to reach a site of interest, assay the soil’s ice content with three-foot-deep drilling and then move on to another location to do it all again. The mission was meant to last 100 Earth days and would trundle a dozen miles across the moon’s surface.
“It’s important from a scientific perspective, but for this whole ‘lunar economy’ that’s in the works—the concept of in situ resource utilization—it’s really important to know how much water ice is actually there,” says Amanda Hendrix of the Planetary Science Institute.
NASA’s original plan for VIPER was to spend $433.5 million building the rover, with a target launch date in 2023. But to accommodate delays with the rover’s ride to the moon—a lander called Griffin developed by the private company Astrobotic—NASA decided in 2022 to push the mission’s launch date to late 2024. The agency has now assessed that neither VIPER nor Griffin will be ready to fly until at least September 2025, which NASA says would raise the mission’s cost through 2026 to $609.6 million (leaving aside the $323 million paid out to Astrobotic).
In a July 17 press briefing, officials said that canceling the rover would save $84 million while also preventing deep cuts to the agency’s Commercial Lunar Payload Services (CLPS) program, which aims to land NASA instruments on the moon with privately owned robotic landers. “Decisions, of course, like this are never easy, and we’ve not made this one in any way lightly,” said Nicola Fox, associate administrator for NASA’s Science Mission Directorate, during the briefing.
“Lipstick on a Pig”
NASA usually takes pains to telegraph a troubled mission’s upward-ticking odds of cancellation. The agency’s Psyche mission, which launched in 2023 to explore a metal-rich asteroid of the same name, went through a grueling review of its delays and cost overruns before it eventually flew. In past cases where missions ran into difficulties but their spacecraft were already built, U.S. government agencies have usually opted for delaying their launches rather than outright killing them.
By contrast, VIPER’s abrupt end follows months of highly visible milestones toward liftoff. In March NASA’s Ames Research Center, which led VIPER’s design, hosted a live stream of the rover’s construction. In May the VIPER team received approval for their plans to stress-test the rover. By the time of the July 17 press conference, VIPER had already been fully assembled and had passed vibration testing.
Signs of budgetary calamity were late-breaking and few; in June a report from the U.S. Government Accountability Office warned that VIPER’s budgetary allotment for fiscal year 2024 would run out in July. But even as late as two weeks ago, senior NASA officials gave no public hint that VIPER was on the chopping block. At a July 10 presentation for NASA’s Planetary Science Advisory Committee, NASA deputy associate administrator for exploration Joel Kearns acknowledged that VIPER and Griffin would not launch in late 2024, as previously estimated. He said nothing about the mission potentially ending, however.
In the July 17 press conference, Fox and Kearns emphasized that other NASA lunar missions were still on track and that versions of VIPER’s instruments would fly on other missions.
“This is a tough and disappointing decision—we all know that—which we had to make in an uncertain and constrained budget environment,” Kearns added in a presentation at the annual NASA Exploration Science Forum on July 23. “But we do believe that this is the way for us to continue to support a portfolio of lunar science and our dedication to studying the moon.”
In interviews with Scientific American, scientists emphasized that VIPER’s whole was more than the sum of its parts. Future CLPS rovers are targeting sites in the moon’s lower latitudes, not the ice-rich poles. An upcoming CLPS mission called PRIME-1 will attempt to land a drill near the moon’s south pole as soon as the end of this year. That spacecraft will provide data on water ice from only one location, however, rather than the many that VIPER had promised.
“I’m very concerned about the messaging NASA is giving in terms of, ‘Oh, well, we don’t really need to do VIPER because we’re doing these other things,’ because what VIPER was going to do is absolutely unique,” says Benjamin Greenhagen, a planetary scientist at the Johns Hopkins University Applied Physics Laboratory and chair of the Lunar Exploration Analysis Group, which advises NASA on lunar science matters.
NASA “is putting lipstick on a pig” with its positive spin on VIPER’s cancellation, adds Clive Neal, a lunar scientist at the University of Notre Dame. “Given what those other missions are going to do and what VIPER is going to do, the difference in the science return is orders of magnitude.”
A Billion-Dollar Budget Hole
During the July 17 briefing, Fox and Kearns stressed that NASA’s budget woes were mostly to blame for VIPER’s doom. Under a 2005 law, NASA must get authorization from Congress to spend any extra money on a mission that overshoots baseline costs by more than 30 percent. VIPER’s approach of that threshold triggered a review of the mission in June. And under strict budget rules passed last summer, there’s vanishingly little room for NASA to reallocate funds.
In June 2023 the Biden administration and congressional Republicans struck a deal to suspend and then raise the U.S.’s debt ceiling, averting a default on the national debt. But in exchange, the deal enacted a two-year freeze on spending levels for NASA and other nondefense federal agencies. This constraint has blown a billion-dollar hole in NASA’s planned science budget. In response, the agency has been forced to propose wide-ranging cuts, including a premature end to the Chandra X-ray Observatory.
In a draft NASA budget released on July 9, the House of Representatives’s Committee on Appropriations recommended giving between $458 million and $533 million to the NASA program that houses VIPER—up to $75 million more than the Biden administration had asked for. While this language would give NASA some flexibility to boost VIPER’s funding, it also creates a zero-sum game because Congress hasn’t signaled that it will raise NASA’s overall science budget.
“The money would have to come from another project,” says Casey Dreier, chief of space policy at the Planetary Society. “They care but not enough to ‘solve the problem,’ as it were.”
Technical difficulties also played a role in VIPER’s downfall, most notably with Griffin, the Astrobotic-built lunar lander meant to carry the rover to the moon. At the time Astrobotic received its contract, it had never flown a moon mission before; to manage this risk, NASA directed Astrobotic to do more testing, agreeing to delay launch from 2023 to 2024. This past January Astrobotic launched its first-ever mission to the moon as part of NASA’s CLPS program. But in a devastating turn, the mission’s lander suffered a critical failure shortly after liftoff, preventing it from reaching the moon at all.
According to Kearns, Astrobotic completed a review of that inaugural mission’s failure and is assessing whether to makes changes to Griffin in response. The situation with Griffin “could even lead, potentially, to a situation ... where NASA could start wondering if the performance reliability of the lander was commensurate with the high value that we have invested in a major payload such as VIPER,” Kearns said during the July 23 NASA forum.
This past weekend, lunar scientists began organizing in a last-ditch attempt to sway Congress, circulating an unusually terse open letter calling on Congress to refuse to authorize VIPER’s cancellation. “The decision to cancel the project at this stage, after spending $450 million, is both unprecedented and indefensible,” the letter reads.
As of July 23, the letter had garnered more than 1,000 signees, according to Johns Hopkins University planetary scientist Ben Fernando, one of the letter’s authors.
Racing against Time—And China
If VIPER doesn’t fly, some U.S. scientists fear that China may take the lead on lunar resource prospecting. The country’s ambitious moon program has seen a string of recent successes, including the first-ever soft landing and sample-return mission on the far side of the moon. China’s next two robotic moon missions, Chang’e 7 and Chang’e 8, will be hunting for water ice near the south pole and testing technologies for a future lunar science base. Chang’e 7 is slated to launch in 2026, with Chang’e 8 to follow in 2028.
“This is a tight race, and currently, the rate at which China is progressing is far faster than us,” says Akbar Whizin, a planetary scientist at the Southwest Research Institute.
“We’re having issues with actually accomplishing some of the basic goals of these missions, which is to land and take measurements.”
There is still a possibility, however slim, that VIPER will fly on board Griffin—even without NASA’s ongoing involvement. In a statement to Scientific American, Astrobotic reaffirmed its commitment to launching its lunar lander. “The decisions must be made quickly, but we’re considering all options,” said Astrobotic CEO John Thornton.
NASA has called for international partners and U.S. private companies to submit expressions of interest in taking over VIPER at no extra cost to the U.S. government. The August 1 deadline for those proposals is fast approaching, however, and there are only a handful of entities on the planet with the money and wherewithal to adopt VIPER.
“Basically, [there’s] almost zero time,” Whizin says. “But this [mission] is already a private-public partnership—so these are interesting, uncharted waters.”