Friday 27 December 2013

The origin of the Bosumtwi Impactor.

Lake Bosumtwi is an 8 km diameter roughly circular lake about 30 km to the southeast of Kumasi in the Ashanti Province of Ghana. It is thought to have been created by a large meteorite impacting the Earth roughly 1.07 million years ago during the Late Pleistocene; the impact crater being roughly 10.5 km in diameter, with the lake sitting in a central depression. Tektites (glassy particles thought to be formed as ejecta from impact craters) associated with this site are found over a large area in neighboring  Côte d'Ivoire.

In a paper published on the online arXiv database at Cornell University Library on 15 May 2013, a team of scientists led by Mattia Galiazzo of the Institute for Astrophysics of the University of Vienna examine the origin of the Bosumtwi Impact Crater, and attempt to determine the origin of the object that caused it.

The Lake Bosumtwi impact crater, Ghana. University of Texas at Austin.

It has perviously been calculated that the Bosumtwi Impactor was probably an ordinary chondrite, 750 m - 1 km in diameter that impacted at a velocity in excess of 15 km per second, and probably over 20 km per second. It has furthermore been suggested that in order to create the field of tektites in Côte d'Ivoire, it must have impacted from the northeast at an angle of between 30° and 45°.

The location of Lake Bosumtwi. Google Maps.

Working from this data Galiazzo et al. attempted to build a model of the position of the Earth and direction of impact at the time of the impact event, in order to determine the origin of the impactor. Based upon this model they conclude that the impactor probably originated within the Middle Main Asteroid Belt, and furthermore that it probably had an orbit highly inclined to the plain of the Solar System, possibly as much as 75°. This places it within a group of asteroids including 2002 MO3, 2009 XF8, 2002 SU and 2010 RR30, which have not been studied as a cluster, but which may well share a common origin.

The orbit of 2002 MO3. JPL Small Body Database Browser.

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