Royal Astronomical Society Press Release
RAS PN 10/29 (NAM 14) 14-Apr-2010
Dust may be a nuisance around the house but it plays a vital role in the formation of the key ingredient for life on Earth – water – according to researchers at Heriot-Watt University. The results from pioneering experiments to solve one of the mysteries of the interstellar space, where did all the water come from, will be presented by Victoria Frankland at the RAS National Astronomy Meeting in Glasgow on Wednesday 14th April.
“We think that the Earth’s water was delivered by comets during the early stages of Earth’s history and that comets were formed from interstellar material left over after the birth of the Sun, but the next step back has been unclear,” said Ms Frankland.
Water is relatively abundant in the interstellar medium and hydrogen atoms are extremely common, but there is a problem with the other vital ingredient for H2O. Gas phase reactions that can take place in the interstellar medium are limited by the low temperatures and pressures. Experiments show that it is possible for hydrogen atoms to combine with molecules of oxygen (O2) or ozone (O3) under the conditions of the interstellar medium. However, observations by recent satellite missions have detected very little gaseous molecular oxygen (O2) and ozone (O3) has never been detected at all in these regions of space. On the other hand, atomic oxygen (O) is quite plentiful, but gas phase reactions between hydrogen and atomic oxygen can’t account for the amount of water observed. Even the observed quantities of atomic oxygen suggest that some is ‘missing’ in star-forming regions compared to the rest of interstellar space.
W5 Molecular Cloud (NASA/JPL-Caltech/Harvard-Smithsonian CfA/ESA/STScI/DSS)