This discovery is earth-shattering – literally.
Researchers from Australian National University have found a 400-kilometre wide impact zone in central Australia from a massive meteorite that broke into two pieces just before slamming into the Earth.
The crater, which is two kilometres underground in an area near the borders of South Australia, Queensland and the Northern Territory, is now the largest impact site ever discovered on Earth.
“The two asteroids must each have been over 10 kilometres across – it would have been curtains for many life species on the planet at the time,” said Dr Andrew Glikson, lead researcher from the ANU School of Archaeology and Anthropology.
“Large impacts like these may have had a far more significant role in the Earth’s evolution than previously thought.”
While researchers think the crater could be around 300 million-years-old, they are yet to locate a plume of ash in nearby sediments, which would be present after an impact.
“It’s a mystery – we can’t find an extinction event that matches these collisions. I have a suspicion the impact could be older than 300 million years,” says Dr Glikson.
Meteorites are the last stage in the existence for space rocks. Before they were meteorites, the rocks were meteors. Before they were meteors, they were meteoroids. Meteoroids are lumps of rock or metal that orbit the sun.
Meteoroids become meteors when they crash into Earth’s atmosphere and the gases surrounding them briefly light up as “shooting stars.” While most meteors burn up and disintegrate in the atmosphere, many of these space rocks reach Earth’s surface in the form of meteorites.
Dr Andrew Glikson with a sample of suevite - a rock with partially melted material formed during an impact [Image: D. Seymour]
Dust-sized particles called micrometeorites make up 99 percent of the approximately 50 tonnes of space debris that falls on the Earth’s surface every day.
More than 60,000 meteorites have been found on Earth. Scientists have divided these meteorites into three main types: stony, iron, and stony-iron.
A Whole Lot Of Holes
Meteorites crash through the Earth’s atmosphere with tremendous force. The largest meteorites leave enormous holes in the ground called impact craters.
The best-preserved impact crater in the world is the Barringer Meteorite Crater, near Winslow, Arizona. There, more than 50,000 years ago, a meteorite weighing about 270,000 metric tonnes slammed into the Earth with the force of 2.5 million tonnes of TNT. The impact blasted a hole one kilometre wide and about 230 metres deep. The fragments left of the space rock show that it was an iron meteorite.
More than a hundred impact craters have been identified on Earth. Perhaps the most famous is the Chicxulub Crater, in Yucatan, Mexico. The Chicxulub Crater can be identified on land, beneath dozens of meters of sediment, although about half of the feature is submerged in the Gulf of Mexico. It is one of the larges impact craters ever discovered on Earth.
Despite its size, the Chicxulub Craber is famous for another reason. Many scientists think the large meteorite that created the Chicxulub Crater—measuring roughly 10 kilometres wide—triggered the extinction of the dinosaurs and other animal and plant life 65 million years ago.
Meteorites crash through the atmospheres of all planets and moons in our solar system. Some planets and moons don't have enough atmosphere to break apart meteors, resulting in large meteorites. These larger meteorites create deep, round impact craters that can be found all over our Moon, Mercury, and Mars.
In 2005, the first meteorite found on another planet was discovered by Opportunity, one of NASA’s Mars rover spacecraft. In 2014, Opportunity’s sister spacecraft, Curiosity, discovered a meteorite that was two metres wide, making it the largest yet discovered on Mars.