More secrets will come be disclosed about the comet Hartley 2 on Thursday, when a small US robot spacecraft, the Deep Impact, will pass within 435 miles of the orbiting bundle of dust, ice and rocks.

The Deep Impact will make use of its powerful telescopes and cameras to capture pictures of the surface and record gas outbursts.

The collected data will be sent back to earth, where scientists will analyze it to explore more about the comet. NASA Scientists have found that the more they come to know about comets the more mysterious they appear to be.

Commenting on the topic, Dr. Mark Bailey, of Northern Ireland's Armagh Observatory said, "The more probes that we fly past them, and the more differences we find. Goodness knows what we are going to find this time at Hartley
2."

On July 4, 2005, the Deep Impact, which is travelling at a speed of 12.5 kilometres per second, flew by comet Tempel 1, capturing data about its surface. Using the Deep Impact for the second mission has saved NASA around 90 per cent of the cost.

The comet Hartley 2 was discovered by Australian astronomer Malcolm Hartley in the year of 1986.