Dating the age of the earth
Research groups in Australia found the oldest mineral grains on Earth.These tiny zirconium silicate crystals have ages that reach 4.3 billion years, making them the oldest materials found on Earth so far. The rocks and zircons set a lower limit on the age of Earth of 4.3 billion years, because the planet itself must be older than anything that lies on its surface.Fifty thousand years ago, a rock hurled down from space to form Meteor Crater in Arizona.Shards of that asteroid have been collected from the crater rim and named for the nearby Canyon Diablo.However, because plate tectonics constantly changes and revamps the crust, the first rocks have long since been recycled, melted down and reformed into new outcrops.
Samples in Western Australia run 3.4 to 3.6 billion years old.
Gravitational interactions coalesced this material into the planets and moons at roughly the same time.
By studying other bodies in the solar system, scientists are able to find out more about the early history of the planet.
Although no rocks have been deliberately returned from Mars, samples exist in the form of meteorites that fell to Earth long ago, allowing scientists to make approximations about the age of rocks on the red planet.
Some of these samples have been dated to 4.5 billion years old, supporting other calculations of the date of early planetary formation.
The nearest body to Earth, the moon, does not suffer from the resurfacing problems that cover Earth's landscape.