Scientists Confirm Moon Formed Within Hours After 4.5-Billion-Year Impact, Drifting 3.8 Centimeters a Year
Updated
Updated · spacedaily.com · Aug 11
Scientists Confirm Moon Formed Within Hours After 4.5-Billion-Year Impact, Drifting 3.8 Centimeters a Year
2 articles · Updated · spacedaily.com · Aug 11
Summary
NASA-backed impact simulations indicate debris from a Mars-sized body striking early Earth coalesced into a moon-sized object within hours, far faster than earlier models that stretched to millions of years.
Apollo moon rocks helped cement the giant-impact theory because their chemistry closely matches Earth's mantle, undercutting older capture, spin-off and co-formation explanations.
Laser measurements using Apollo reflectors show the Moon is still receding by about 3.8 centimeters a year as tidal friction slows Earth's rotation and transfers energy outward to the lunar orbit.
Ancient tidal sediments and Babylonian eclipse records trace the same process back in time, showing a 21.9-hour day 620 million years ago and day lengthening by roughly 1.8 milliseconds per century.
That long retreat will eventually end total solar eclipses on Earth, with NASA scientists estimating the last one will occur in about 600 million years.