Speaking today at the BA Festival of Science in Exeter to promote his latest book, 'Rhythms of Life', Professor Russell Foster, from Imperial College London and Charing Cross Hospital, an expert on circadian rhythms which determine the timings of the body's own internal clock, will warn about the less well known dangers of space exploration.

Professor Foster is part of an international team working with experts from the National Space Biomedical Research Institute, a consortium established in 1997 through NASA, looking at potential health problems caused by space travel.

Professor Foster comments: "While many of the technical difficulties of space travel are well documented, there has been less research on the medical and health related problems astronauts may encounter, especially the possible effects on an astronaut's ability to get enough sleep and adjust their physiology to the varying demands of activity and rest.

"The human body is used to a 24 hour cycle, which may prove difficult to regulate in space. For example, Mars has an extra 39 minutes on its rotation, while the International Space Station has a cycle which is only 90 minutes long. These variations can cause considerable disruption to sleeping patterns with considerable knock on health effects."

The body's clock is relatively insensitive to light, and to keep body time aligned to day and night requires considerably more light than is needed to read. In the absence of a strong light re-setting cue our clocks will drift and become desynchronised with the 24h day. While a bright blue midday sky can be up to 100,000 lux, and standard domestic or office lighting is around 100-300 lux, the light environment in space is much lower, often as little as 10 lux. With these low levels of light it is not possible for the body clock to properly adjust the circadian body clock, and sleep patterns become disturbed leading to a range of ill health problems ranging from mild to severe.

Previous research has shown that disrupted sleep patterns can lead to a number of health problems. Night shift workers may suffer from sleep disorders, poor vigilance, an increased chance of accidents, gastro-intestinal disease, an increased incidence of cardiovascular disease, and there is some evidence of a link with early onset diabetes. In addition it has been found that night shift workers are at a 50 percent increased risk of a car crash at 3am after 4 successive night shifts. Unless we are very careful these conditions will be duplicated in space, with potentially fatal consequences on the long-duration missions to Mars.

Professor Foster adds: "Our bodies' circadian rhythm is crucial to us. It stops everything happening at once, and co-ordinates the right things to happen at the right time. Peak performance is demanded in nature, and this is particularly so in the challenging environment of space. You can't be half asleep or half awake, and being so, may ultimately prove catastrophic."