Thursday, 11 February 2016

Meteorite unlikely to have killed man in Tamil Nadu.

Indian newspaper The Hindu carried a report on Sunday 7 February 2016 in which the death of a man and injury of three other people as well as causing damage to several nearby buildings at the campus of a college in Vellore, Tamil Nadu, were described as having been caused by a meteorite. This is in theory possible; large meteor imapcts are known to have caused considerable damage on the past, with airburst explosions such as the 2013 Chelyabinsk Meteor and 1908 Tunguska Bolide having caused damage and injuries (but no recorded deaths), while smaller objects have damaged homes and vehicles on numerous occasions and larger structures such as Meteor Crater in Arizona are attributed to prehistoric impacts. However experts in the field have questioned the likelyhood of this event being linked to a meteor impact for several reasons.

Police inspect the site of a suspected meteor impact in Vellore, Tamil Nadu, on Saturday 6 February 2016. The Hindu.

Firstly, in order for a meteor to impact the ground it must be derived from a parent body several meters across. Such small asteroids are now routinely searvhed for by a number of specialist sky-watching surveys looking for Near Earth Objects before they come close to the Earth, as well as other astronomical surveys that continuously observe the sky for other phenomena. Even if such bodies reaches the Earth undetected they will result in visible fireballs (meteors brighter than Venus) in the upper atmosphere as they explode due to friction induced heating high in the atmosphere, with any fragments reaching the ground several minutes later. Such Fireballs are typically observed by large numbers of people, and in the twenty first century seldom excape being recorded by CCTV, dashboard cameras and even people armed with camera phones, but there are no recordings or reported sightings of the 6 February 2016 Vellore incident.

Secondly pictures of an object described as the meteorite released by authoriies in Vellore are not suffiiently clear to enable clear identification. Meteorites (actual pieces of rock that fall to Earth, as opposed to meteors, which are shooting stars, bright lights in the sky caused by objects burning up in our atmosphere) have a distinctive surface patterna, caused by superheating as they pass through the atmosphere, which usually enables experts to identify them quickly, and even without this examination of the minerals will quickly enable their identifcation. No such images have emerged of the Vellore object, leading experts outside India to question its nature.

The only available image of the Vellore 'meteorite'. Tamil Nadu Police.

If the explosion was not cuased by a meteorite, then its actual nature remains to be identified. The most likely explanation is an explosion of strictly terrestrial nature, such as a malicious explosive device or malfunctioning piece of machinery. An a;ternative explanation would be a piece of debris falling from an aircraft. or possibly even a piece of space junk (part of a setellite in low Earth orbit or a discarded launch vehicle) that could fall to Earth without sufficient friction to cause a visible fireball (such a piece of space junk would accelerate towards the Earth under the influence of gravity, whereas asteroids have additional velocity from their own orbit around the Sun, meaning that they hit the atmosphere at far higher speeds).

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