On Saturday 2 June, just before 19:00 SA Standard Time, a small asteroid approximately 2m across, entered and exploded in the Earth's atmosphere above Southern Africa.

In this event, a seismometer called SUR detected the explosion at 0.3-0.5 kilotons. An explosion of one kiloton has the power of one ton of TNT.  The atomic bomb at Hiroshima was about 15 kilotons in size.

The SUR hosted at the Sutherland site of the South African Astronomical Observatory (SAAO), is part of the Global Seismographic Network (GSN) through Project IDA (International Deployment of Accelerometers).

The Mt. Lemmon Survey (Catalina Sky Survey, Arizona) first observed the object at 09:32 Universal Time Coordinated (UTC), just over 7 hours before it entered our atmosphere at a speed (relative to the Earth) of 17 km/s (over 60,000 km/h).
 
The Catalina Sky Survey is one of the international, optical astronomy programmes, which aims to discover such Near-Earth asteroids, with a focus on advanced detection of objects that could threaten the Earth. 

These programmes are all currently located in the Northern hemisphere, which creates a gap in the sky coverage and allows some asteroids to go undetected.  To mitigate this problem, the SAAO is currently collaborating with NASA to install a telescope in Sutherland that will scan the entire sky, every night, searching for dangerous Near-Earth asteroids. 

This telescope will form part of the Asteroid Terrestrial-impact Last Alert System (ATLAS), which has additional telescopes monitoring from Hawaii. The Sutherland ATLAS is expected to go on sky in 2020.  The recent event highlights the practical benefits of optical, ground-based astronomy and the worldwide need for immediate South African contributions in this field.
 
Impacts on the Earth by very large bodies are very rare, but it is generally thought that an impact by a comet, 65 million years ago, was responsible for the extinction of the dinosaurs. Comets are similar to asteroids but composed mainly of ice.

Issued by the Department of Science and Technology

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