Image: Estelle Greenwood
OK, so you’ve got this idea for a Sci-Fi movie:
Scene one: A lonely Arizona astronomer locates a small asteroid. He finds that it is going to collide with Earth within hours.
Scene two: Across the globe, frantic astronomers launch a desperate attempt to find out as much as they can about the object, before it slams into the atmosphere.
Scene three: Cut to the Nubian desert of Sudan. The pre-dawn sky ignites as the asteroid, turned meteor, explodes at high altitude. The event is witnessed by the crew of a nearby Jumbo, imaged by a range of satellites and even recorded by the early-warning system of the US military. As the Sun rises over the desert, a streaky cloud trail is the only remaining hint of the event that has just taken place.
Scene four: Could any fragments have survived and reached Earth? An intrepid research scientist working for the SETI institute thinks so. Together with local scientists and students, he launches a recovery expedition to the desert region close to where debris would have landed.
Scene five onwards: The expedition locates fragments of the meteorite. Tensions ensue with commercial dealers who join the hunt for further fragments. A worldwide scientific effort is launched to analyse the meteorite and these confirm that it has a highly unusual composition. It contains traces of amino acids and is part of a world that was destroyed early in the history of our Solar System.
Of course, none of this is science fiction, but the true life adventure of Asteroid 2008 TC3, which crashed to Earth on 7 October 2008. The small two-to-five metre diameter object was spotted by Richard Kowalski of the Catalina Sky Survey, using the 1.5 metre telescope at Mount Lemmon, Arizona. With only about 20 hours before impact, the astronomical community was alerted and the object was tracked by about 27 groups of amateur and professional observers worldwide. Technically classed as a meteor once it had entered the Earth’s atmosphere, asteroid 2008 TC3 was travelling at a velocity of 12.8 kilometres a second (29,000 mph) when it exploded at a height of 37 kilometres (121,000 feet).
A search of the desert in December 2008, organised by Dr Peter Jenniskens (SETI Institute and NASA) and Muawia Shaddad (University of Khartoum), resulted in the recovery of fifteen pieces of the meteorite, with a total mass of about 0.5 kg. Further searches were organised by the University of Khartoum and these have increased the total number of recovered fragments to 600, with a combined weight of 10.3 kilograms. An additional 40 meteorites were collected by an independent group and these were shipped abroad and sold commercially. The area covered by debris from Asteroid 2008 TC3, technically referred to as a strewn field, measures 30 x 7 km. All the recovered fragments of the meteorite have been given the collective, official name of Almahata Sitta, after a nearby train station, which translated from Arabic means “Station Six”.
So what sort of meteorite is Almahata Sitta? In the finest tradition of the Sci-fi genre: To be continued…….