NASA have determined that the Yarrabubba meteor crater in Australia is the oldest known crater on Earth at 2.229 billion years old.
The Yarrabubba takes the title from the 200-kilometer Vredefort Dome crater in South Africa. The purpose of dating these meteor craters is to determine the effects these impacts had on the environmental development of the planet.
“Scientists wonder how meteor impacts might relate to the formation of the continents. We also would like to know when the frequency of meteor impacts declined to the point where life could emerge and thrive,” said Timmons Erickson, a research scientist with the Astromaterials Research and Exploration Science division, or ARES, at NASA’s Johnson Space Center. “These are all big questions in the field of science.”
The original crater is believed to have been 70 kilometers across, though its remnant today is only 20 kilometers, since it has been worn away by wind, rain and other natural forces, leaving only overgrown rocky outcrops and ridges.
The team dated the crater by searching for rocks that showed signs of being subjected to the shock and heat of a meteor strike. They gathered rock samples that contain two minerals: zircon and monazite. The minerals are crystals that contain uranium and lead, the ratio of which can be measured to determine the age of rock. The scientists then measured the uranium and lead in those crystals to calculate their age.
The timing of Yarrabubba’s impact coincides with the formation of some of Earth’s earliest icecaps and glaciers, shortly after the emergence of oxygen in the atmosphere.