Is there life on other planets?
Scientists reckon that the chances of life somewhere else in the Universe are high enough to spend hundred of millions of dollars searching for it, but they are more doubtful about extraterrestrial life in our own Solar System. Life depends on two-dozen chemical elements, of which carbon, hydrogen, oxygen, nitrogen, sulphur and phosphorus are the most important. For life to continue, light and warmth are needed. Mars has the right chemical ingredients and may once have had the right conditions. A 4.5 billion-year-old meteorite from Mars, found in Antarctica, contains what some scientists think is a fossilised microbe that may have lived on the 'Red Planet'. Conditions now, including subzero temperatures, are not suitable for life on Mars. They may, however, be kinder on Europa, one of Jupiter's moons. Satellites have photographed ancient river valleys on Europa, and they may still be water below its ice cover.

Tight squeeze
In space, people grow larger, by up to 5 cm (2 in), because there is no gravity to pull their body parts downwards. This increase in size can cause problems. On one Shuttle mission, the astronauts found they had grown so much that they could hardly squeeze into a tigh-fitting chair that they wre supposed to sit in for an important experiment.