NASA Swift Satellite Spots Mars-Bound Siding Spring Comet Shedding Water

Scientists have gotten a bit of a closer look at the comet Siding Spring, thanks to NASA's Swift satellite. In late May, the satellite managed to image the comet, which is headed for an astonishingly close brush with Mars later this year.

"Comet Siding Spring is making its first passage through the inner solar system and is experiencing its first strong heating from the sun," said Dennis Bodewits, one of the researchers, in a news release.

Formerly known as C/2013 A1, the comet is composed of a clump of frozen gases mixed with dust. As it travels, Siding Spring will throw off this gas and dust-especially as it approaches the sun. Different gases will stream from the frozen nucleus of the comet as they heat, carrying with them large quantities of dust that reflect sunlight and brighten the comet.

Now, though, researchers have gotten a closer look at exactly how much water that this comet might shed during its passage. While instruments can't detect water molecules directly, they can detect light emitted by fragments formed when ultraviolet sunlight breaks up water.

"Based on our observations, we calculate that at the same time of the observations the comet was producing about 2 billion billion billion water molecules, equivalent to about 13 gallons or 49 liters each second," said Tony Farnham, one of the researchers, in a news release.

By estimating how much water this comet is shedding, the researchers can also estimate its size. The scientists believe that the icy nucleus of the comet is only about 2,300 feet across. This places it at the lower end of a size range that was estimated from earlier observations by spacecraft.

The findings reveal a bit more about this comet, and may shed light on the activity and evolution of comets as a whole.