Washington, Dec 14 (IANS): Scientists are working on the best and safest way to grab a sample of a rotating comet racing through space at 150,000 miles per hour, spewing chunks of ice, rock and dust. The idea is to get a look at biomolecules in comets that may have assisted the origin of life.

An option is to fire a harpoon at the comet from a spacecraft hovering above to rapidly acquire samples from specific locations with surgical precision.

Using this technique would allow samples to be collected even from areas that are much too rugged or dangerous to permit the landing and safe operation of a spacecraft.

Comets are frozen chunks of ice and dust left over from our solar system's formation. As such, scientists want a closer look at them for clues to the origin of planets and ultimately, ourselves.

Scientists at NASA's Goddard Space Flight Center in Greenbelt are in the early stages of working out the best design for a sample-collecting comet harpoon.

"One of the most inspiring reasons to go through the trouble and expense of collecting a comet sample is to get a look at the 'primordial ooze' - biomolecules in comets that may have assisted the origin of life," says Donald Wegel of NASA Goddard and project engineer.

Wegel places a test harpoon in the bolt carrier assembly, steps outside the lab and moves a heavy wooden safety door with a thick plexiglass window over the entrance, according to a NASA statement.

After dialling in the desired level of force, he flips a switch and, after a few-second delay, the crossbow (ballista) fires, launching the projectile into a 55-gallon drum full of cometary simulant -- sand, salt, pebbles or a mixture of each.

The ballista, a large crossbow nearly six feet tall, produces a uniquely impressive thud upon firing, somewhere between a rifle and a cannon blast.

"We had to bolt it to the floor because the recoil made the whole testbed jump after every shot," said Wegel.