Sometime in the 2030s, after decades of planning, a multibillion-dollar joint NASA and ESA effort should haul some Mars rocks back to Earth for in-depth study.
Unless, that is, newly proposed policies from President Trump are allowed to take effect. In a document released late last week filled with brutal budget cuts for broad swaths of the federal government, the Trump administration called for canceling the endeavor, formally known as Mars Sample Return (MSR). Our top story has the details—as well as reactions of outrage and despair from many Mars-focused planetary scientists.
Granted, MSR has had more than its fair share of troubles, exhibiting disturbing amounts of cost growth and schedule slippage. Then again, NASA and its partners had already flagged these issues and were developing detailed plans to address them. And some degree of flexibility should be allowed for a mission that is so ambitiously complex: MSR's first phase already began with NASA's Perseverance rover landing in Jezero Crater in 2021 to gather samples, and now the next steps call for an as-yet-unbuilt NASA lander to stow and launch them into orbit. Once aloft, they'll rendezvous with an ESA-provided spacecraft for collection and return to Earth, ultimately followed by retrieval and careful study of the precious material in state-of-the-art terrestrial laboratories.
All that careful planning and hefty investment, it's hoped, could lead to the first compelling detection of life beyond Earth; if for instance microbes ever managed to emerge on Mars, most astrobiologists would agree that the ancient rocks of Jezero Crater would seem to be a near-ideal place to look for their microscopic remains.
The Trump administration's notional replacement for MSR would be crewed human missions to Mars, which it says could achieve the same goals. That, however, is only partially true at best: Crewed exploration would be far, far more expensive than MSR ever could be, and is almost certainly farther-off in the future as well. But the most worrisome aspect of astronauts gathering samples is that their very presence on the Red Planet could irreversibly contaminate that material with Earthly biology in ways that utterly undermine the search for life. An appeal to Apollo-style "boots and flagprints" on Mars to plug an MSR-sized hole is dubious, to say the least.
More immediately, the bigger problem unleashed by an MSR cancellation would be the damage done to U.S. international partnerships. ESA and its European member states have invested heavily in the project, and if it goes away most of those costs would not really be recouped. How much longer Europe and other allies can or will tolerate sweeping and spastic changes in U.S. space policy before simply abandoning us to make other plans is unclear, but their patience surely is wearing thin.
Not all is yet set in stone: Technically speaking, Congressional appropriators will have the last word and should begin their work in earnest once the White House's full budget proposal is released in late May or early June. Stay tuned—perhaps MSR can yet be saved. —Lee Billings
