Chinese scientists have formally announced the discovery of Earth's longest meteorite strewn field in Altay, the Xinjiang Uygur autonomous region.

Experts from the Purple Mountain Observatory in Nanjing, Jiangsu province, made the announcement on Oct 13 after studying the chemical composition of three meteorites and discovering that they were all from the same parent asteroid.

The earliest known discovery of extraterrestrial stones in the field was in 1898, when herdsmen in the Gobi Desert found a silvery camel-shaped stone weighing 28 metric tons.

The Meteoritic Society later named it Armanty, and confirmed it to be the world's fourth-largest meteorite.

More than 100 years later, a second one was found. It weighed 430 kg and was named Ulasitai.

But it was not until 2011, when the 5-metric-ton Wuxilike was uncovered, that scientists began to notice that the three meteorite were in a line that stretched across 425 km.

"They are on the same axis from southeast to northwest, which piqued our interest," said Xu Weibiao, meteorite curator with the observatory under the Chinese Academy of Sciences.

Tests revealed that all three meteorites were composed of the same chemical components and microelements, as were several smaller rockers found in the field.

"This suggests that the meteorites were all from the same parent asteroid before it separated as it entered the Earth's atmosphere," Xu said.

An ordinary meteor shower can scatter meteorites across dozens of kilometers.

Before the finding in Altay, the world's largest meteorite strewn field was Gibeon, with a long axis of 275 km.

Judging by the 425-km strewn length of the Altay field, its meteor shower was likely the largest on the Earth.

However, there is no historical documentation on the incident, so scientists speculate it might have happened prehistorically.

"A meteor shower of such a scale must have had a great impact on the Earth," Xu said. "If it happened after humans walked the earth, we often find cave painting depicting the incident in the area."

He said the team had used isotopic dating to determine when the meteor shower occurred.

An average of 20,000 meteorites fall to the Earth every year, which scientists use to determine information about the universe.

For example, evidence of volcanic activity on Mars 200 million years ago was discovered by sampling a meteorite.

In 2017, China will launch the Chang'e-5 lunar probe, which will collect rock samples from the moon.

"For the moon sample research, the observatory will use more advanced analytical equipment, which will greatly assist our petrological and mineralogical research," Xu said.

(China Daily 10/28/2016 page5)