Chasing oxygen
The Infrared Space Observatory (ISO) has detected Water inthe planetary nebula NGC7027. The ISO is ideally suited for observations, since it is outside the earth's atmosphere, which acts a major absorber of infrared radiations. Thus a major advance has been made in solving the "missing oxygen problem". The amount of oxygen observed is only half as much as one would infer from solar observations. Theoretically, oxygen will exist mostly in the form ofwater molecules and oxygen gas. The ISO result has generated considerable excitement in astronomers who are now waiting for more results from ISO and other forth- coming space missions to solve the mystery of missing oxygen. (Nature, March 21,1996).