Space probe heading for comet collision

A Nasa spacecraft released a probe early today on a collision course with a speeding comet in an ambitious mission that scientists hope will offer the first look inside one of these icy bodies.

Deep Impact released its barrel-sized “impactor” on a suicide journey that is expected to climax tomorrow when the comet Tempel 1 smashes into it.

The high-speed crash should be visible from parts of the Western Hemisphere.

Comets contain the frozen primordial ingredients of the solar system and studying them could provide clues to how the sun and planets formed.

NASA says an impact will not significantly change the comet’s orbital path around the sun, so the $333m (€279m) experiment poses no danger to Earth.

The 820lb (372-kilo) copper probe successfully separated from the mothership to set the stage for the collision with the comet, according to mission control at Nasa’s Jet Propulsion Laboratory in Pasadena. Electrical wires connecting the spacecraft broke, springing free the probe.

Scientists are counting on the collision to carve a stadium-sized crater in Tempel 1, a pickle-shaped comet half the size of Manhattan now about 80 million miles (130 million kilometres) from Earth. No explosives are needed since the energy from the impact will be similar to detonating nearly five tons of TNT.

It is the first attempt by the US space agency to catch a glimpse of the pristine core of a comet.

Mission scientists have acknowledged the project’s difficulties. Among the challenges is making sure the probe stays on course as it hurtles toward the comet without guidance from mission control.

There is also the chance that the cloud of gas and dust surrounding the comet’s nucleus may damage the spacecraft and probe and prevent data transmissions back to Earth.

Comets are blobs of ice and dust that orbit the sun and were born about 4.5 billion years ago – nearly the same time as the solar system itself. When a cloud of gas and dust condensed to form the sun and planets, comets formed from what was left over. Studying them could shed light on how the solar syste formed.

Tempel 1, an oblong-shaped comet discovered in 1867, moves around the sun in an elliptical orbit between Mars and Jupiter every six or so years.