American culture and cinema often glorifies space travel, from the heroic early adventurers of “The Right Stuff” to the more recent rescue of Matt Damon’s astronaut character from Mars in “The Martian.”

But the reality is less glamorous, with journeys into deep space posing serious dangers to astronauts that include inadequate food, radiation exposure and heightened risks of developing cancer and other maladies. And NASA is not yet ready to handle those dangers as it moves ahead with plans to send the first human mission to Mars by the 2030s, according to a recent audit.

NASA inspector general Paul K. Martin found that the legendary space agency “faces significant challenges” ensuring the safety of any Mars-bound astronauts,  and that its schedule to limit the risks is overly “optimistic.” As a result, he said, Mars crews likely will have to accept more risks to their health and safety than their predecessors who went to the moon and work in the International Space Station.

“NASA has taken positive steps to address the human health and performance risks inherent in space travel,” Martin wrote in the 48-page report. He added: “Long duration missions will likely expose crews to health and human performance risks for which NASA has limited effective countermeasures. … Accordingly, the astronauts chosen to make at least the initial forays into deep space may have to accept a higher level of risk than those who fly International Space Station missions.”

A spokeswoman for NASA referred questions to the agency’s response contained in the report, which said it concurred with Martin’s recommendations for improvement, such as ensuring that cost estimates for steps to better protect astronauts are accurate. “NASA has been working in all of these areas for some time,” the agency wrote. “Thus, the report represents a validation of, rather than a correction to, NASA’s … plans and the challenges ahead.”

NASA is aiming to send a crew to the Martian surface by the 2030s, the latest iteration of a plan proposed by President George H. W. Bush in 1989. But despite the publicity generated by the recent box-office success of “The Martian,” experts say serious technical challenges remain, and NASA’s flat budget won’t pay for a Mars mission.

On top of those obstacles, it’s not yet clear whether the government can keep astronauts safe. Martin’s report outlines a series of deep space risks that include altered gravity that produces loss of bone density and muscle strength, and space radiation that could lead to cancer, degenerative tissue diseases and central nervous system changes.

Even nutrition, the report said, could be problematic, because any Mars vehicle will likely be significantly smaller than the International Space Station, and astronauts will be too far away to receive the regular resupply missions they now get on the station.

“Space flight is an inherently risky endeavor,” the report says. “Apart from the tremendous engineering challenges in launching and returning astronauts safely to Earth, humans living in space experience a range of physiological changes that can affect their ability to perform necessary mission functions.”

The report said NASA is improving its process for mitigating these risks, and agency officials recently said the next Mars rover, scheduled for launch in 2020, will have instruments that can extract oxygen from the Martian atmosphere. Officials said that is progress toward eventually helping astronauts live off the land on Mars.

But the report concludes that progress needs to quicken.

22 stunning photos of our solar system and beyond in 2016

In this undated photo provided by NASA, Saturn's icy moon Mimas is dwarfed by the planet's enormous rings. Consider it a cosmic carousel with countless rings up for grabs. NASA’s Saturn-orbiting spacecraft, Cassini, has begun an unprecedented mission to skim the planet’s rings. On Tuesday, Nov. 29, 2016, Cassini got a gravitational assist from Saturn’s big moon Titan. That put the spacecraft on course to graze Saturn’s main outer rings. (NASA/JPL-Caltech/Space Science Institute via AP) (AP)