The hunt for planets similar to the Earth could be hampered by low water levels, Cambridge scientists have said.
Three planets which orbit stars similar to the sun had been seen as ideal candidates for detecting water vapour - a key characteristic of Earth-like climates.
But a team of astronomers using Nasa's Hubble Space Telescope studying HD 189733b, HD 209458b, and WASP-12b - which are between 60 and 900 light-years away, with temperatures ranging from 900 to 2200C - have found the planets are virtually dry.
Scientists from the Institute of Astronomy at the University of Cambridge said it highlighted the challenges in searching for planets capable of sustaining life.
They found water levels which are only one-tenth to one-thousandth of the amount predicted.
Dr Nikku Madhusudhan of the University of Cambridge said