A team of scientists from the University of Gothenburg in Sweden discovered evidence of massive meteorite impacts, which are believed to have been formed by two simultaneous strikes that occurred over 450 million years ago.
Geophysics professor Erik Sturkell and his colleagues at Gothenburg found the two meteorite craters in the historic county of Jämtland.
One of the craters was measured at less than five miles in diameter while the second crater, located nine miles away, was close to a tenth of the size of the first.
Sturkell said that the meteorite strikes happened at the same time, around 458 million years in the past, eventually forming the two enormous craters.
The recently discovered meteorite impacts were not the only ones to hit the Earth during this era.
Sturkell explained that around the same period, about 470 million years ago, a pair of massive space rocks collided in the asteroid field between Jupiter and Mars, causing hundreds of fragments to be thrown off in different directions. Many of these space rock fragments crashed on Earth, including the two that formed the Jämtland craters.
At the time, the county of Jämtland was still submerged in 500 meters of water where the two meteorites impacted the planet. Such double impacts of meteorites are occurrence, with the Jämtland craters serving as the first of its kind to be categorically proven by scientists.
Sturkell said that data collected through drilling operations provide evidence of identical sequences being present in the two meteorite impacts, while the samples of the sediment gathered from above the impact sequences show that the two craters are of the same age. This proves that the massive craters are indeed caused by simultaneous impacts.
When the space rocks hit the Earth, water was forced away from the impact, leaving the massive craters entirely dry for at least a hundred seconds.
According to the researchers, the water later went rushing back in, carrying along fragments of the meteorites along with ejected material from the resulting explosion. The gigantic wave also tore away sections of the sea bed.
Over the years, several other meteorites have also been discovered in Sweden's Kinnekulle area.
Sturkell said that during the 1940s, an odd-looking slab of red limestone was unearthed from one of the quarries in the area. It was later discovered that the slab had traces of meteorite in it.
Sturkell pointed out that larger pieces of meteors typically explode and break almost entirely, while smaller pieces of meteors crash as rocks, such as the case of the limestone slab.
Scientists have found close 90 pieces of meteorites from impacts on Kinnekulle in the past fifteen years.
