The Hubble space telescope has uncovered a distant planet with carbon dioxide in its atmosphere – an important step forward in the search for extraterrestrial life. Water vapour and methane have also been detected on HD 189733b, which is 63 light-years away and about the size of Jupiter.Although the planet is far too hot to sustain life, astronomers hope the techniques that allowed them to detect these compounds – which can be evidence of life – will lead to a breakthrough in the hunt for distant Earth-like planets."The carbon dioxide is kind of the main focus of the excitement, because that is a molecule that under the right circumstances could have a connection to biological activity as it does on Earth," said Mark Swain of NASA's Jet Propulsion Laboratory in Pasadena, California.