An Esa experiment carried out by astronauts on the ISS has found the cosmos is less hostile to space travellers than expected.

It had been thought that cosmic radiation may severely limit the time an astronaut can spend in space without seriously risking their life.

Using a 'phantom' human covered in thousands of detectors, the research showed that levels of radiation had been significantly overestimated - and deep space travel could be fairly safe.

An experiment run by Esa on the ISS using a 'dummy' human (shown) has found radiation levels for astronauts in space are less than thought. The findings suggest deep space travel for humans could be safe. Here the dummy is shown being put in a casing to simulate the spacesuit of an astronaut

The experiment involved placing a mannequin in direct exposure to cosmic radiation, twice inside the ISS and once outside in space.

Known as Matroshka, the legless torso consists of 33 slices of 'human matter' each one inch (2.5cm) in thickness.

This includes real human bones to simulated the shape and density of soft tissues and lungs in the human body.

Inside the slices was measuring equipment to measure the amount of incoming radiation.

The overall conclusion was that dosimeters worn by crew on the ISS, which measure radiation exposure, had overestimated that actual radiation does they received by 15 per cent.

WOULD A MARS MISSION BE FATAL TO ASTRONAUTS? Back in October a study claimed sending people to Mars may be impossible due to an increased radiation risk from cosmic rays when the sun is less active during the solar minimum. It's thought that a predicted decrease in solar activity, which occurs every 11 years, will raise the levels of radiation astronauts are subjected to from cosmic rays on a deep space mission. This will increase the risk of suffering sickness, cancer and more on lengthy trips to the red planet lasting about a year to levels beyond what is considered safe. The research, published in the journal Space Weather and led by Dr Nathan Schwadron of the University of New Hampshire, found that a 30-year-old astronaut can spend about one year in space before cosmic rays raises the radiation-risk beyond safe exposure limits. However, this new research by Esa could suggest the levels are safer than expected. Advertisement

Amazingly, outside the ISS in open space this overestimation exceeded 200 per cent.

From the results of the Matroshka experiment the scientists concluded that travel of astronauts to the Moon or to Mars may be somewhat safer in terms of their radiation hazard than expected.

Nevertheless, the doses the space travellers are likely to receive, even though being lower than thought earlier, would still remain dangerously high.

But while Mars might previously have been limited to a year or so, now the time taken to explore Mars could potentially be extended.

'One may say that we found open space to be a bit less hostile to humans than expected,' said Dr Paweł Bilski, an Associate Professor at the Institute of Nuclear Physics of the Polish Academy of Sciences (IFJ PAN) in Kraków, Poland.

'The effective doses, related to the health risk of the astronauts and calculated from measurements with our detectors, were lower than those indicated by dosimeters worn by the astronauts.'

However, he added further information from beyond low Earth orbit would be needed to verify the findings.

'We must remember that measurements within the Matroshka experiment were performed at low Earth orbit where the Earth's magnetosphere significantly reduces the number of charged particles from cosmic radiation,' he said.

'In interplanetary space there is no such shielding.'

This is the interior structure of the phantom used in the experiment Matroshka, which contains slices of human bones. The white tubes contain sets of thermoluminescent detectors. Half of these detectors was manufactured by the Institute of Nuclear Physics of the Polish Academy of Sciences in Kraków, Poland

The Matroshka phantom is seen here with astronauts Siergiej Krikaliew and John Philips on board of the International Space Station. Radiation levels were measured both inside the station and outside in open space using the human-like dummy

WHAT ARE COSMIC RAYS? A long-standing puzzle in astrophysics is the source of ultra-high-energy particles from space that hit Earth. Called cosmic rays, they're up to a billion times more energetic than particles at Cern's Large Hadron Collider. They strike the atmosphere and cause an enormous shower of other particles, mostly muons, electrons and photons, over a wide area. Though they were discovered decades ago, cosmic rays at these high energies are very rare, making it difficult to pinpoint where in the universe they originated. It's thought that some come from supernovas, but it's likely there are other sources of cosmic rays in the universe as well. Advertisement

The main hazard to the astronaut's health due to exposure to cosmic radiation is the increased probability of developing cancer in his or her body.

This probability however is quite dependent on the type of radiation the astronaut is exposed to.

Most of the natural sources of ionising radiation on Earth produce electromagnetic radiation of high energy - gamma rays.

On the other hand, in cosmic rays, energetic protons or heavier ions dominate, which are much more effective in creating cancer cells.

The mannequin on board of the International Space Station (ISS), with thermoluminescent and plastic detectors inside its 'body', was also dressed in a 'poncho' with additional detectors, simulating the personal dosimeters worn by astronauts.

Thus, doses recorded by individual dosimeters of the ISS crew could be compared with those actually absorbed inside their bodies.

Over the years 2004 to 2009 the Matroshka mannequin underwent three exposures to cosmic radiation, each lasting a year of more.

Two of these exposures occurred inside the Russian modules of the space station and for one exposure the phantom, in a container imitating the shielding properties of a spacesuit, was placed in open space outside the ISS. Such measurements have never been done before.