Earth and Moon May Be Younger Than Thought - But Not By Much

"Earth and Moon Are Younger Than Thought "
Space.com (June 10, 2010)

"Earth is not exactly getting its youth back, but a new study has determined that the collision from which the Earth and moon were formed may have occurred much later than previously thought, making our planet and moon younger than scientists had commonly believed.

"The Earth and the moon were created as a result of a giant collision between two planets the size of Mars and Venus. Until now, it was believed that the collision occurred when the solar system was 30 million years old – roughly 4.5 billion years ago.

"But, according to a new study that was recently published in the scientific journal Earth and Planetary Science Letters, the true age of the Earth and moon can be determined by examining the presence of certain radioactive elements in the Earth's mantle.

"The results of the research show that the Earth and moon must have formed much later than previously thought – perhaps up to 150 million years after the formation of the solar system. That makes our home planet a bit younger than scientists thought...."

Let's look at those numbers:

• 4,500,000,000: age of Earth
  • Roughly, according to previous research
• 4,350,000,000: age of Earth
  • Roughly, according to this research

150,000,000 years is a long time, compared to the lifespan of a human being - or a sequoia. But the current estimate is 96.6% of the previous one. Significant, yes, but not all that big.

It's sort of like the difference between being 45 years old and halfway between birthdays, and being 43 years old with a birthday coming in about four months.

The Space.com article describes how the new date of the Earth-Moon system's formation was determined. And, gives a really short description of how two planet-size bodies apparently collided to form the Earth and Moon we know.

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• "A Serious Search for Other Worlds, Life, and - Maybe - Extra-Terrestrial Intelligence"