US President Donald Trump last week laid out one of the biggest challenges ever for NASA — to land the first humans on Mars.
But his detailed budget request for the fiscal year 2026 also proposed cancelling dozens of the space agency’s missions, including projects to study Earth, Mars and Venus. And the next day, on 31 May, Trump pulled his nomination for NASA chief, the businessman and commercial astronaut Jared Isaacman.
All of this has left the space agency in turmoil, and the scientists who normally participate in NASA’s missions split over whether they support the push for the red planet.
A budget shortfall
NASA has wanted to put people on Mars for decades, but both technological and budget limitations mean that likely would not happen until the 2040s under current plans. Trump wants to accelerate that timeline. On 30 May, the White House proposed spending some US$1 billion in 2026 on Mars plans, including research into new spacesuits and an astronaut landing system. “These investments will provide the technologies necessary for future Mars exploration and eventual crewed missions to Mars,” the NASA budget plan said.
Trump proposes unprecedented budget cuts to US science
If the space agency really does want to focus on sending humans to Mars, space-policy specialists say, it will need to massively ramp up its spending. A human mission to Mars would likely cost hundreds of billions of dollars spread over a number of years; the agency currently spends $25 billion a year on all of its programmes, and Trump has proposed cutting that to under $19 billion. “Right now, with the budgets that are proposed, we can’t afford to send people to Mars,” says John Grunsfeld, an astrophysicist and former NASA astronaut who led the agency’s science programmes from 2012 to 2016.
Trump’s latest rhetoric on Mars echoes decisions he made during his first term as president, when, in 2017, he announced that NASA would send astronauts back to the Moon. In 2022, the agency tested a mega-rocket that is intended to achieve that objective, but that mission, Artemis I, was uncrewed. Many technical challenges remain before people can be put on the lunar surface — a goal currently slated for 2027.
One challenge is achieving success with the giant Starship vehicle, built by the aerospace company SpaceX in Hawthorne, California. Once NASA’s mega-rocket has propelled astronauts into lunar orbit, they will rendezvous with Starship, which will fly them to the Moon’s surface. But Starship has yet to orbit Earth successfully, much less demonstrate the frequent launches and in-space refuellings needed for the Moon landing; its most recent test flight ended in an explosion on 27 May.
Days after that blowup, Elon Musk, the billionaire chief executive of SpaceX who has advised Trump, said he still hoped to launch the first Starship to Mars next year. Some scientists have been put off the idea of landing humans on Mars by Musk’s involvement. The technology entrepreneur has long talked of colonizing the red planet, but with little consideration of societal ethics or international norms. In recent months, he led the Trump administration’s efforts to downsize the US government and slash its science funding, even as SpaceX is likely to compete for billions of dollars’ worth of government contracts on the quest for Mars.
A tough environment
Others are more excited about the prospect of landing people on the red planet. NASA has overseen missions to Mars many times before, sending a series of robotic spacecraft, including the Curiosity and Perseverance rovers. Some researchers say that astronauts could explore more quickly and gain better insight into whether Mars has ever hosted extraterrestrial life. “If we definitively want to answer the question of whether Mars had life or has life today, I think we have to send humans,” says Tanya Harrison, a planetary scientist with the Outer Space Institute who is based in Ottawa, Canada.
NASA’s Perseverance rover has drilled numerous rock cores on Mars that are now awaiting collection and delivery back to Earth.Credit: NASA/JPL-Caltech/Del-4Ri
But even those in favour caution that a journey to Mars would not only be costly — taking funding away from numerous other research programmes — it would also pose many physical risks. On the way to Mars, astronauts would face extreme isolation and higher doses of deadly space radiation over longer periods than they have ever been exposed to on the Moon or on space stations. If they successfully land on Mars, they would have to get out of their capsule without collapsing after the zero-gravity voyage; begin working in a frigid environment where the soil is full of toxic chemicals and there is almost no air to breathe; and deal with abrasive dust storms1.
There are solutions, such as living inside an underground lava tube that was created by volcanic activity, which could offer protection against radiation and dust storms. But visiting Mars will be like visiting Antarctica — another hostile, perilous environment — with vastly greater risks, scientists say. “I want to disabuse people of the assumptions that they have that humans are going to be fine,” Erik Antonsen, a researcher in space physiology at Massachusetts General Hospital in Boston, said at conference on human space exploration on 28 May.
