Washington: Comet Siding Spring, which will brush very close to Mars later this year, is producing a lot of water - around 50 litres every second - according to NASA.
"Based on our observations, we calculate that at the time of the observations the comet was producing about 13 gallons or 49 litre of water each second," said Tony Farnham, a senior research scientist at University of Maryland College Park (UMCP) in the US.
At this rate, comet Siding Spring could fill an Olympic-size swimming pool in about 14 hours, but scientists established that the comet poses no danger to spacecraft now in orbit around Mars.
Comets contain some of the most ancient material scientists can study.
They cast off gas and dust whenever they venture close to the sun.
NASA's Swift satellite imaged the comet Siding Spring in late May.
These optical and ultraviolet observations are the first to reveal how rapidly the comet is producing water and allow astronomers to better estimate its size.
"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, an astronomer at UMCP.
As the comet approaches the sun and becomes heated, different gases stream from the nucleus, carrying with them large quantities of dust that reflect sunlight and brighten the comet.
The Swift observations are part of a larger study to investigate the activity and evolution of new comets.