* Astronomy

A U.S. congressman has suggested using a Russian radar together with American optical systems to monitor asteroid threats to Earth. The suggestion came during the discussion of a NASA funding bill approved by the House of Representatives on Wednesday.

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Until very recently, the devastating 1908 explosion of a space rock over the isolated Tunguska region of Siberia was thought to be a once-in-a-millennium event. Based on comparisons to nuclear weapon blast effects, many experts estimated the Tunguska object to be 50 to 100 meters. But new simulations by Mark Boslough at Sandia National Laboratories suggest the Tunguska object was much smaller than previously believed. And since smaller near-Earth objects (NEOs) are more common than larger ones, the implication is that the gap between such impacts may be centuries rather than millennia.

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At a news conference  Anatoly Perminov, Russian Space Agency chief, has announced that there were plans to develop a space defence system that would protect the Earth from a potential asteroid impact by 2040.
Members of the scientific community are unanimous in that the asteroid danger is real and that some measures should be taken to prevent it. The discovery of Apophis three years ago made them and the general public even more aware of that threat.
Scientists suggest monitoring all space objects that fly in dangerous proximity to the Earth. This will require 5-meter telescopes, with three or four mounted in each hemisphere. The telescopes will target some particular segment of outer space, and data collected with their help could then form the foundation of a catalogue of asteroids measuring more than a kilometre across.
Installed on board a spacecraft, telescopes with a mirror 20 to 30 centimetres in diameter could monitor asteroids measuring 50-100 meters across at a distance of several million kilometres from the Earth. The main objective of such monitoring will be to follow the trajectory of objects that may have a potential impact on the Earth.
Scientists say that after at least 90% of large asteroids are recorded and constantly observed, it will be possible to warn the humankind about the threat of an impact some 80-100 years ahead.
But it remains unclear how a sighted asteroid can really be stopped from striking the Earth. Would it be a good idea to preempt an impact by hitting the approaching celestial body with a nuclear or hydrogen bomb? And at what distance would such a pre-emptive strike be safe enough for the planet?
Mathematical modelling has enabled scientists to calculate the lower distance limit for detonating a nuclear warhead in outer space. An asteroid moves with an average speed of 25 kilometres per second, so it should be no closer to the Earth than 464,000 kilometres when a bomb targeting it goes off.
Detractors argue that using such a method would be extremely unwise and fraught with grave implications for the Earth.
Boris Shustov, president of the Astronomy Institute at the Russian Academy of Sciences, is one of the opponents. He heads an academic task force set up in Russia to study threats posed by asteroids and comets to the Earth.

Source Novosti

A NETWORK of mirrors harnessing the destructive power of the sun might save the world from disaster, space experts believe.

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