Deep Impact 'could help Earth'
2005-07-01 07:29
Paris - An extraordinary US mission to whack a passing comet may indirectly provide a windfall for guardians monitoring any space rocks that could hit Earth.
The Nasa probe Deep Impact is to eject a 372kg projectile that on Monday is scheduled to smack into Comet Tempel 1 as the heavenly wanderer flies past Earth at a great distance.
The collision, occurring at 37 100 kph could gouge a crater as big as a football stadium and spew out a mass of cometary gas and dust, eagerly recorded by telescopes, radars and spectrometers.
The goal behind the $333m mission is to uncover the inner secrets of one of the solar system's strangest phenomena.
Comets are believed to comprise primitive material created in the early solar system and, say some experts, may hold organic molecules that may have been the chemical building blocks for creating life on Earth.
But comets can also be bringers of death, too.
Deep Impact could yield precious data
The long reign of the dinosaurs is believed to have been snuffed out some 65 million years ago when a comet smashed into modern-day Mexico, kicking up a pall of dust that obscured the Sun and chilled the climate.
Scientists involved in Near Earth Objects (NEOs) - comets and asteroids that may pose a threat to our home - say Deep Impact could yield precious data.
"The more we know the better, and there might be some surprises in this mission," David Harris, chairperson of a NEO advisory panel set up by the European Space Agency (ESA), said.
"We might learn something crucial about the structure of comets that could help us in the event that we faced something like this."
The risks posed by NEOs must be put into context, for the probability of any collision is extremely remote.
A stepped-up US-led effort to scour the skies for this threat has not yielded any prospect of a hit, although several rocks could make near-misses in coming decades.
But any collision would carry astronomical costs. Smaller objects measuring two or three hundred metres across could devastate a region or trigger a tsunami, while larger ones could be climate-crushers.
In this respect, Deep Impact, the 1998 sci-fi movie about a doomsday comet, was not wrong, and the threat from NEOs is gaining credibility among politicians.
Only a fraction of potentially risky asteroids - the rocks that circle the Sun between Mars and Jupiter and which can sometimes be jostled into a different orbit - has been identified and their orbits mapped.
And nothing is known about types of comets, mercifully rare, that take centuries to orbit the Sun. Never spotted before, these could hurtle out of almost nowhere, giving mankind very little time to react.
As to what that response should be, two main options present themselves: to send a space tug to gently deflect the rock to a different trajectory or to blow the brute up, Hollywood-style.
Both are dependent on knowledge about the density and structure of the comet or asteroid - and this is where Deep Impact comes in.