by Staff Writers
Paris (AFP) July 24, 2014
A study of unprecedented detail has revealed astonishingly little water on three distant planets, hinting at potential obstacles in the search for Earth-like worlds rich in H2O, astronomers said Thursday.
Using the Hubble Space Telescope, a team conducted detailed measurements of the atmospheres of three gas giants orbiting stars similar to our Sun, expecting to find "lots of water".
Between 60 and 900 light years from Earth, these worlds are so hot, with temperatures between 900 and 2,200 degrees Celsius (1,650-4,000 Fahrenheit), that they were thought to be ideal candidates for detecting water vapour.
The researchers, however, "have come up nearly dry," said a statement from Cambridge University, which took part in the research.
"The low water abundance we are finding is quite astonishing," said research leader Nikku Madhusudhan of the university's Institute of Astronomy.
"These results show just how challenging it could be to detect water on Earth-like exoplanets in our search for potential life elsewhere."
One of the planets, dubbed HD 209458b, was subject to the highest-precision measurement of any chemical compound ever carried out on a planet outside our solar system, the team said.
The other two were HD 189733b and WASP-12b.
The three planets had between one-tenth and one-thousandth the amount of water predicted by standard planet-formation theories, said the statement.
"As we prepare to search for biosignatures on rocky (Earth-size) exoplanets in the future we should be prepared to find planets with significantly less water than our expectations based on Earth," Madhusudhan told AFP by email.
Future telescopes searching for signs of water may now need to be designed with higher sensitivity to account for the possibility of planets being significantly drier than predicted.
The finding also "opens a whole can of worms" in the existing theory of planet formation, Madhusudhan added.
Under the accepted theory, giant planets form around young stars on a cosmic "disc" composed of hydrogen, helium and ice and dust particles.
The dust particles stick together, forming larger and larger grains drawn together by the gravitational forces of the disk.
The forming planet core may continue attracting solid matter and gas until it becomes a gas giant, whose atmospheric oxygen had been thought to be largely in the form of water.
"The very low levels of water vapour found by this research raise a number of questions about the chemical ingredients that lead to planet formation," said the statement.
One possibility is that the primordial disks the planets came from may have contained less water than previously thought.
The team used Hubble to study the planets as they passed in front of their parent stars, looking for signature water vapour influence on the starlight shining through the gas giants' atmosphere, as seen from Earth.
Lands Beyond Beyond - extra solar planets - news and science
Life Beyond Earth
|The content herein, unless otherwise known to be public domain, are Copyright 1995-2014 - Space Media Network. All websites are published in Australia and are solely subject to Australian law and governed by Fair Use principals for news reporting and research purposes. AFP, UPI and IANS news wire stories are copyright Agence France-Presse, United Press International and Indo-Asia News Service. ESA news reports are copyright European Space Agency. All NASA sourced material is public domain. Additional copyrights may apply in whole or part to other bona fide parties. Advertising does not imply endorsement, agreement or approval of any opinions, statements or information provided by Space Media Network on any Web page published or hosted by Space Media Network. Privacy Statement All images and articles appearing on Space Media Network have been edited or digitally altered in some way. Any requests to remove copyright material will be acted upon in a timely and appropriate manner. Any attempt to extort money from Space Media Network will be ignored and reported to Australian Law Enforcement Agencies as a potential case of financial fraud involving the use of a telephonic carriage device or postal service.|