(SPACEVIEWS) Hot interstellar gas clouds can contain ten thousand times as much water than colder clouds, a discovery that may be difficult to reconcile with current theories, a team of astronomers reported this week.

In a special issue of the publication Astrophysical Journal Letters, astronomers said that cold interstellar gas clouds with temperatures as low as minus 405 degrees Fahrenheit (minus 243 degrees Celsius, 30 Kelvins) may have as little as a few parts per billion of water vapor in them.

"That's far less than predicted by most theories and presents a real puzzle to our understanding of the chemistry of interstellar clouds," said Ronald Snell of the University of Massachusetts.

By contrast, warm interstellar gas clouds, heated by the presence of nearby young stars to temperatures of thousands of degrees, can contain up to 10,000 times as much water as their colder counterparts, according to astronomers.

"We can think of these stellar nurseries as giant chemical factories that are producing water vapor at a tremendous rate," said David Neufeld of the Johns Hopkins University. "The large amounts of water vapor present in regions of star formation will help the interstellar gas to cool, perhaps eventually triggering the birth of a future generation of stars."

These and other findings come from data collected by NASA's Submillimeter Wave Astronomy Satellite (SWAS), a spacecraft launched into low Earth orbit in December 1998 to look for water, molecular oxygen, as well as other elements and compounds in star-formation regions such as interstellar clouds.

Astronomers also used SWAS to detect traces of water vapor in the atmospheres of gas-giant planets Jupiter and Saturn.

"The water vapor we've detected in the gas giants is almost certainly the result of bombardment by small icy particles that come from interplanetary space and are rapidly vaporized once they hit the planetary atmosphere," said Ted Bergin of the Harvard-Smithsonian Center for Astrophysics. "The water molecules within these icy particles may well have originated as water vapor in the interstellar gas cloud that formed the solar system more than four and a half billion years ago."

SWAS data also confirmed that the tenuous atmosphere of Mars is essentially saturated with water vapor. "However," said Mark Gurwell of the Harvard-Smithsonian Center for Astrophysics, "since Mars is so cold, the total amount of atmospheric water is a several thousand times less than in the Earth's atmosphere."

SWAS continues to return data and perform as designed. However, potential cuts in NASA's space-science budget and a re-evaluation of the agency's science priorities could force the mission to end at the end of fiscal year 2001, in October of next year.