The search to discover planets similar to our own could be hindered by low water levels, scientists have warned.
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 this raises new questions about how expo-planets form and highlights 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.
"These very hot planets with large atmospheres orbit some of our nearest stars, making them the best possible candidates for measuring water levels, and yet the levels we found were much lower than expected," Dr Nikku Madhusudhan said.
"These results show just how challenging it could be to detect water on Earth-like exo-planets in our search for potential life elsewhere."
He added that more sensitive instruments may be needed on the next generation of telescopes in order to find the "holy grail" of a planet similar to Earth.
"It basically opens a whole can of worms in planet formation," Madhusudhan said.
"We expected these planets to have lots of water in their atmospheres.
"We have to revisit planet formation and migration models of giant planets, especially hot Jupiters, to investigate how they're formed.
"There are so many things we still don't understand about exo-planets; this opens up a new chapter in understanding how planets and solar systems form."
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