Dating billion year old rocks

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.

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The nearest body to Earth, the moon, does not suffer from the resurfacing problems that cover Earth's landscape.

As such, rocks from early lunar history should be present on the moon.

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.

As science progressed, these methods were proven to be unreliable; for instance, the rise and fall of the ocean was shown to be an ever-changing process rather than a gradually declining one.

In an effort to calculate the age of the planet, scientists turned to the rocks that cover its surface.

By using not only the rocks on Earth but also information gathered about the system that surrounds it, scientists have been able to place the age of the Earth at approximately 4.54 billion years.

For comparison, the Milky Way galaxy that contains the solar system is approximately 13.2 billion years old, while the universe itself has been dated to 13.8 billion years.

More than 70 meteorites have fallen to Earth to have their ages calculated by radiometric dating.

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