Many people yearn to see the beauty of glowing meteors crossing the dark sky. Meteors are actually extraterrestrial dust or small objects that burn in the atmosphere as they reach Earth and start to glow. Larger objects that cannot be burned up become meteorites and fall to the ground. When even larger celestial objects such as asteroids or comets collide with Earth, the atmosphere can hardly reduce their speed. They will impact the ground with hypervelocity at more than 35 times the speed of sound, a speed equivalent to flying from Tsim Sha Tsui to Fo Tan within one second, and the collision will result in the creation of impact craters.
People who want to learn more about impact craters should visit the exhibition entitled "Xiuyan Impact Crater", which will be held at the Hong Kong Space Museum (Space Museum) from today (August 24) until November 28. The exhibition describes the formation of impact craters, and introduces the Xiuyan Crater, China's first confirmed impact crater.
The exhibition is jointly presented by the Leisure and Cultural Services Department, the Guangzhou Institute of Geochemistry of the Chinese Academy of Sciences and the Beijing-Hong Kong Academic Exchange Centre.
There are 178 confirmed impact craters on Earth, mainly in North America, Europe and Australia. The first confirmed impact crater in China is the Xiuyan Crater. It is located in Manchu Autonomous County of Xiuyan in Anshan City, Liaoning Province. In early 2007, a research group led by Dr Chen Ming, a researcher from the Guangzhou Institute of Geochemistry of the Chinese Academy of Sciences, began their investigation in Xiuyan. Xiuyan Crater was confirmed to be an impact crater in 2009 and was included in the authoritative Earth Impact Database in 2010.
The diameter of the Xiuyan Crater, a simple bowl-shaped crater locally known as "Luoquanli", is approximately 1,800 metres, which is about the distance between Tsim Sha Tsui and Yau Ma Tei, and its depth is around 150 metres, more or less equivalent to 50 storeys.
At the exhibition, visitors will also be able to see a sample rock from the drilled cores under a microscope and an animated simulation of the formation of the Xiuyan Crater.
The Space Museum is located at 10 Salisbury Road, Tsim Sha Tsui. It is open from 1pm to 9pm on Mondays, Wednesday to Friday, and from 10am to 9pm on Saturdays, Sundays and public holidays. It is closed on Tuesdays (except public holidays). Admission to the exhibition is free.
For enquiries, please call the Space Museum on 2721 0226.
Ends/Wednesday, August 24, 2011
A panoramic view of Xiuyan Crater, located in Anshan City, Liaoning Province. It was confirmed to be an impact crater in 2009 and is the first confirmed impact crater in China. It was included in the authoritative Earth Impact Database in 2010.
The picture shows a high-density crystal, coesite, which is formed at high pressure. When shock wave pressure reaches 50 GPa, quartz becomes molten silicon dioxide. As the pressure reduces to 2.6 GPa to 13 GPa, coesite crystallises from the molten silicon dioxide. The Xiuyan Crater was confirmed as an impact crater because the research group found a large amount of coesite in the drilled cores.
The picture shows impact-produced breccia drilled from beneath the centre of the Xiuyan Crater.