First Known Example Of An Asteroid Hitting A Mountain Found In China

A cirque-shaped depression on the top of a mountain in Northeast China’s Jilin province is likely a crater formed by an asteroid impact. If so, it is the first known example of an impact crater found on the summit of a mountain.

Baijifeng mountain is composed mainly of sandstone, with a small amount of granite, deposited over 500 million years ago in a shallow sea. Later tectonic movements tilted and folded the sediment layers forming a mountain chain. Most mountain ranges on Earth formed in a similar way, but a 1.6-kilometer-wide gap—unlike any tectonic feature—separates the two twin peaks of Baijifeng mountain.

Intrigued by the unusual shape, a research team led by Ming Chen of the Center for High Pressure Science and Technology Advanced Research in Shangai studied the rocks debris scattered on the mountain, discovering evidence of shock metamorphism as experienced only during the impact of an asteroid on Earth.

Based on the statistics of the 200 impact craters recognized so far on Earth, the number of craters in China is far below the world average, and to date, only two impact structures have been confirmed in China.

The 1.8-kilometer-wide Xiuyan Crater is located in Liaoning Province. Its exact age is unknown. In 2021, a partially buried basin in Heilongjiang Province was confirmed to be of extraterrestrial origin. The 1.85-kilometer-wide Yilan Crater is more than 300 meters deep and likely formed in the last 50,000 years. It is one of the most recent impacts on Earth.

Hypervelocity collisions between celestial bodies and the Earth may result in shock metamorphism of the bedrock. The rocks are shattered by shock waves down to the single crystals, forming straight rupture patterns called planar deformation features visible under the microscope. Studying quartz crystals preserved in the sandstone rubble recovered from Baijifeng, the researchers discovered a set of those deformation features. The researchers suggest that the rubble, still showing sharp edges and corners, on the top of the mountain likely represents impact-ejected rock fragments.

The granite of Baijifeng Mountain was formed in the Jurassic Period, with an age of 150–172 million years. Therefore, the Baijifeng impact structure must have been generated after the formation of this granite. Based on the fresh look of the rock fragments covering the impact site, a young age is very likely. The authors think that similar to Yilan Crater, the Baijifeng impact structure formed in the last 100,000 years.

The study “Discovery of the Baijifeng impact structure in Tonghua, Jilin, China” was published in the journal Matter and Radiation at Extremes (2023).

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