Invisible Threats [Dark Comets]

The biggest threat to our little blue planet may turn out to be something that we don't see/detect an approaching deadly comet . Yes, "Dark Comets" are invisible and very hard to detect.

"Dark Comets" are formed when an active comet's reflective water ice has evaporated away, leaving behind an organic crust that only reflects a small fraction of light. Astronomers have previously spotted comets heading towards earth just days before they passed. In 1983 a comet called IRAS-Araki-Alcock passed at a distance of just 5 million kilometres, the closest of any comet for 200 years, but it was noticed just a fortnight beforehand.

A composite of images from NASA's Deep Space 1 spacecraft shows features of comet Borrelly's nucleus, dust jets escaping the nucleus and the cloud-like coma of dust and gases surrounding the nucleus.

Hazardous comets and asteroids are monitored by various space agencies under an umbrella effort known as Spaceguard. UK-based astronomers Bill Napier claim that many comets could be going undetected.

He warns that some of these comets may still be zipping around the solar system. Other observations support their case. The rate that bright comets enter the solar system implies there should be around 3000 dark comets buzzing around, and yet only 25 are known.

Source: Newscientist

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Sam