All the countries had established mobile phone networks relatively early and so made good places to carry out the study."The study suggests there is no substantial risk of this tumour in the first 10 years after starting mobile phone use. They appear close to where people usually place their mobile handsets so it was an obvious choice of cancer for the scientists to investigate.It is estimated that a billion people worldwide use mobile phones so even a small increased risk of cancer could mean that cellphones might be responsible for many thousands of extra brain tumours.However, the scientists said that there was relatively little information on the long-term use of mobiles and they could not rule out the possibility of a risk emerging over time.The study, published in the online journal The British Journal of Cancer, studied 678 people with acoustic neuroma and compared their use of mobile phones over a 10-year period with a group of 3,553 people who had not developed the condition.An international team of scientists selected people in five different countries - Britain, Denmark, Finland, Norway and Sweden - to participate in the study. The findings lend further weight to the mounting evidence showing that mobile phones do not appear to cause serious illnesses - at least in the relatively short period in which they have become commonplace. Scientists at the Institute of Cancer Research in London said yesterday that they found no correlation between a type of brain cancer called acoustic neuroma and the number of years a patient had used a mobile phone.Neither did they find any link between the brain cancer and the length of time someone used a cellphone, the total number of hours the phones were used or the total number of calls that were made.A comparison of older analogue headsets with the newer digital versions also failed to establish any link between the devices and the occurrence of acoustic neuromas in the brain.Acoustic neuromas are benign tumours that grow in the nerve connecting the ear and inner ear to the brain. Using mobile phones regularly for up to 10 years does not cause brain tumours, according to one of the largest studies into the link between cancer and cellphone radiation. An analysis of its atmosphere revealed it was about 91 per cent water vapour, 3 per cent carbon dioxide, 4 per cent nitrogen or carbon monoxide and about 2 per cent organic molecules.Torrence Johnson of Nasa's Jet Propulsion Laboratory in Pasadena, California, said that a heat source beneath the moon's south pole appeared to be evaporating ice and other molecules to regenerate the atmosphere.The heat may be caused by radioactive rocks beneath the moon's surface or by the tidal forces created as the moon orbits Saturn - although neither could generate enough heat to account for the atmosphere, Dr Johnson said.Candy Hansen, a Nasa scientist working on Cassini's ultraviolet instruments, said that half a ton of material a second was ejected from Enceladus's south pole, which would, over the four billion-year lifetime of the solar system, amount to a loss of 5 per cent of the moon's original mass..

Images from the south pole revealed a series of "tiger stripes" that appeared to be deep fractures in the frozen ocean. "It's that strange." The Cassini space probe, which is orbiting Saturn, flew past Enceladus on two occasions, and detected that the moon was unexpectedly distorting Saturn's magnetic field.This led Professor Michele Dougherty of Imperial College London to suggest taking an even closer look, which Cassini did on 14 July with a fly-by that took it within 108 miles of the moon's surface. It was a bit like finding that Antarctica is warmer than the Earth's equatorial regions," he said. Enceladus, which was discovered in 1789 by the English astronomer Sir William Herschel, is one of the coldest places in the Saturn system because its extremely bright, ice-capped surface reflects about 80 per cent of the sunlight that strikes the moon.John Spencer, a Cassini scientist at the Southwest Research Institute in Boulder, Colorado, said the latest findings were unexpected "We had quite a surprise.

Cassini's instruments have measured a temperature of minus 188C at the moon's south pole, which is about five degrees warmer than its equator. But scientists believe they have discovered why the atmosphere of Enceladus seems to be a permanent feature - it is being constantly regenerated by a mysterious source of heat buried deep beneath the moon's south pole.Measurements taken by instruments on the Cassini space probe have shown that far from being the coldest spot on Enceladus, its south pole is in fact the warmest - warmer even than its sun-drenched equator.By Earth standards, the temperatures are nothing to write home about. The latest images of Enceladus, one of the innermost moons of Saturn, also reveal another distinguishing feature of this celestial body - it has an atmosphere. Enceladus is only 500km (310 miles) in diameter, which means it could just fit on a map of England, and in theory such a small moon should not have a big enough gravitational pull to keep its atmosphere from disappearing into space. It looks like a huge ball of ice drifting in space. Stunning new pictures of this moon of Saturn show why - it is covered by a frozen ocean with an average temperature of about minus 200C.