Bad news, potential Martians.
Data gathered from the Curiosity Mars rover on its journey to the Red Planet indicates that astronauts would not be able to travel there without incurring a potentially lethal dose of radiation.
Before the $2.5 billion robot landed on Mars last year, it spent eight months in space travelling to the planet.
The good news, which we already knew, is that the robot made it there unscathed.
The bad news is that had Curiosity had a human companion on its 253-day, 560km trip, the chances are they wouldn't have been so lucky.
Even though the robot was contained within a protective shield designed to ensure its sensitive equipment and computer systems would survive the journey, it still registered very high levels of radiation.
Above: Nasa illustration of the sources of radiation in Deep Space, and how Earth's magnetosphere protects us
The robot's Radiation Assessment Detector counted a radiation dose - mainly from high-energy cosmic rays and solar particles - of about 1.84 milliSieverts per day - roughly equivalent to having a full CT scan once every five days, for months on end.
That dose doesn't include the radiation that would be absorbed during a stay on the planet, or on the return journey.
Nasa currently allows a three percent increased risk of fatal cancer for astronauts aboard the International Space Station, over their entire career. With current tech, a 500-day Mars mission would exceed that level.
Nasa said that the data would aid planning for future Mars missions, but experts admitted it was not possible to safely send astronauts to the planet without improvements in propulsion and shielding technology.
Nasa's associate administrator for human exploration William Gerstenmaier said:
"We learn more about the human body's ability to adapt to space every day aboard the International Space Station. As we build the Orion spacecraft and Space Launch System rocket to carry and shelter us in deep space, we'll continue to make the advances we need in life sciences to reduce risks for our explorers.
Curiosity's RAD instrument is giving us critical data we need so that we humans, like the rover, can dare mighty things to reach the Red Planet."
There are currently several funding attempts in progress to send astronauts to Mars privately, but none have produced full technical details or timetables for their attempts to get to the Red Planet and back.Suggest a correction