The researchers at Virginia Technical University and the Johnson Space Centre in Houston cracked open the meteorite and found it contained little bubbles of salt water.

Writing in the journal Science released on Thursday, they said the water was either in whatever asteroid the meteorite broke off of or was carried onto the asteroid by a comet or some other object carrying water.

The meteorite was one of two that fell in 1998 near the town of Monahans, Texas.

``The fall was witnessed by seven boys, and the first of two stones was recovered immediately,'' the researchers, led by Michael Zolensky, wrote.

``This first stone was carried to the Johnson Space Centre and broken open in a filtered air, clean-room facility less than 48 hours after the fall.''

The scientists found strange purple crystals that turned out to be salt. Careful analysis showed there was liquid water within the crystals.

``The existence of a water-soluble salt in this meteorite is astonishing,'' Robert Clayton of the University of Chicago wrote in a commentary on the study.

Because of the careful conditions under which the meteorite was cracked open, Zolensky and colleagues said they were sure the water was not of earthly origin.

``Two possible origins for the brine are indigenous fluids flowing within the asteroid and exogenous fluids delivered into the asteroid surface from a salt-containing icy object, such as a comet,'' they wrote.

The meteorite is one of a class known as chondrite meteorites, which are assumed to contain some of the most primitive materials from the early solar system.

The researchers said it might help them find out more about the primordial solar nebula -- the hot, spinning disk of dust and gas from which the sun and planets coalesced.