Astronauts on lengthy space missions risk suffering from “space fever”, according to a new study.

Weightlessness resulting from low gravity is linked to an increase in body temperature of about 1C.

Such a change develops gradually over around two-and-a-half months.

Since even small divergences in core body temperature can result in impaired physical and mental performance, this finding could have consequences for lengthy space travel, including missions to Mars.

Moon pictures show traces left by astronauts Show all 11 1 /11 Moon pictures show traces left by astronauts Moon pictures show traces left by astronauts Reuters Moon pictures show traces left by astronauts NASA's Lunar Reconnaissance Orbiter (LRO) image shows the Apollo 17 site on the moon Reuters Moon pictures show traces left by astronauts NASA's Lunar Reconnaissance Orbiter (LRO) image shows the Apollo 17 site on the moon, where the tracks laid down by the lunar rover are clearly visible, along with the last foot trails left on the moon. The images also show where the astronauts placed some of the scientific instruments that provided the first insight into the moon's environment and interior. LRO captured the sharpest images ever taken from space of the Apollo 12, 14 and 17 landing sites. Images show the twists and turns of the paths made when the astronauts explored the lunar surface. NASA says the image brightness and contrast have been altered to highlight surface details. Reuters Moon pictures show traces left by astronauts This annotated image released by NASA shows an image of the Apollo 17 landing site taken by the Lunar Reconnaissance Orbiter Camera(LROC) in orbit around the Moon. The twists and turns of the last tracks left by humans on the moon crisscross the surface in this LRO image of the Apollo 17 site. In the thin lunar soil, the trails made by astronauts on foot can be easily distinguished from the dual tracks left by the lunar roving vehicle, or LRV. Also seen in this image are the descent stage of the Challenger lunar module and the LRV, parked to the east. Getty Images Moon pictures show traces left by astronauts This annotated image released by NASA shows an image of the Apollo 14 landing site taken by the Lunar Reconnaissance Orbiter Camera(LROC) in orbit around the Moon. The paths left by astronauts Alan Shepard and Edgar Mitchell on both Apollo 14 moon walks are visible in this LRO image. Getty Images Moon pictures show traces left by astronauts This annotated image released by NASA shows an image of the Apollo 17 landing site taken by the Lunar Reconnaissance Orbiter Camera(LROC) in orbit around the Moon. The twists and turns of the last tracks left by humans on the moon crisscross the surface in this LRO image of the Apollo 17 site. In the thin lunar soil, the trails made by astronauts on foot can be easily distinguished from the dual tracks left by the lunar roving vehicle, or LRV. Also seen in this image are the descent stage of the Challenger lunar module and the LRV, parked to the east. AFP/Getty Images Moon pictures show traces left by astronauts NASA's Lunar Reconnaissance Orbiter (LRO) image shows the Apollo 17 site on the moon, where the tracks laid down by the lunar rover are clearly visible, along with the last foot trails left on the moon. The images also show where the astronauts placed some of the scientific instruments that provided the first insight into the moon's environment and interior. LRO captured the sharpest images ever taken from space of the Apollo 12, 14 and 17 landing sites. Images show the twists and turns of the paths made when the astronauts explored the lunar surface. NASA says the image brightness and contrast have been altered to highlight surface details. Reuters Moon pictures show traces left by astronauts NASA's Lunar Reconnaissance Orbiter (LRO) image shows the Apollo 17 site on the moon, where the tracks laid down by the lunar rover are clearly visible, along with the last foot trails left on the moon. The images also show where the astronauts placed some of the scientific instruments that provided the first insight into the moon's environment and interior. LRO captured the sharpest images ever taken from space of the Apollo 12, 14 and 17 landing sites. Images show the twists and turns of the paths made when the astronauts explored the lunar surface. NASA says the image brightness and contrast have been altered to highlight surface details. Reuters Moon pictures show traces left by astronauts NASA's Lunar Reconnaissance Orbiter (LRO) image shows the Apollo 17 site on the moon, where the tracks laid down by the lunar rover are clearly visible, along with the last foot trails left on the moon. The images also show where the astronauts placed some of the scientific instruments that provided the first insight into the moon's environment and interior. LRO captured the sharpest images ever taken from space of the Apollo 12, 14 and 17 landing sites. Images show the twists and turns of the paths made when the astronauts explored the lunar surface. NASA says the image brightness and contrast have been altered to highlight surface details. Reuters Moon pictures show traces left by astronauts NASA's Lunar Reconnaissance Orbiter (LRO) image shows the Apollo 17 site on the moon, where the tracks laid down by the lunar rover are clearly visible, along with the last foot trails left on the moon. The images also show where the astronauts placed some of the scientific instruments that provided the first insight into the moon's environment and interior. LRO captured the sharpest images ever taken from space of the Apollo 12, 14 and 17 landing sites. Images show the twists and turns of the paths made when the astronauts explored the lunar surface. NASA says the image brightness and contrast have been altered to highlight surface details. Reuters Moon pictures show traces left by astronauts This image made available by NASA shows paths left by walking astronauts, single lines, and lunar buggy tracks, parallel lines, from the 1972 U.S. Apollo 17 moon mission. NASA's Lunar Reconnaissance Orbiter made this and other photographs of lunar landing sites from 13 to 15 miles above the moon's surface. AP

“This space fever, as we may call it, has potential implications for long-term space flights in terms of astronauts’ health, wellbeing and support,” the researchers wrote in their study, published in the journal Scientific Reports.

This phenomenon has implications for any future spacefaring civilisations, they added, and humans’ evolutionary ability to adapt to climate change.

We have a core body temperature of around 37C, which is controlled within a narrow range by mechanisms like sweating and shivering.

Significant diversions from this temperature can be life-threatening.

To arrive at these findings the researchers studied 11 astronauts before, during and after their stays on the International Space Station.

They kept track of the astronauts’ body temperatures both during exercise and at rest.

Exercise is vital for keeping astronauts fit in space, but during these periods the scientists found the astronauts’ core body temperatures often exceeded 40C.

Severe deviations above 40C can have life-threatening consequences.

The scientists found that core body temperature rose both higher and faster during physical exercise in space than on the ground.

However, the most notable finding was the 1C increase in body temperature even at rest.

“Under weightless conditions, our bodies find it extremely difficult to eliminate excess heat,” said Hanns-Christian Gunga, a space medicine specialist at the Berlin-based university clinic Charité, which led the study.

“The transfer of heat between the body and its environment becomes significantly more challenging in these conditions.”

Essentially, low gravity makes sweat evaporate more slowly, and loss of the ability to properly sweat is the key driver in the development of persistent space fever.

Such deficiencies appear to be particularly prominent during exercise.

“This is in line with anecdotal evidence from cosmonauts complaining about thermal discomfort,” the researchers wrote.

They noted space flight also induced a pro-inflammatory response similar to that produced by the immune system in response to infection, which also affects core body temperature.

The study involved a new technology applied via forehead sensors, which combines a skin surface temperature sensor with a heat-flux sensor, and which is capable of measuring minor changes in blood temperature.

The scientists concluded their results could also have implications for humans who stay on Earth.