Fossil Clam Reveals 372-Day Year 70 Million Years Ago as Earth Spun in 23.5 Hours
Updated
Updated · spacedaily.com · Aug 12
Fossil Clam Reveals 372-Day Year 70 Million Years Ago as Earth Spun in 23.5 Hours
1 articles · Updated · spacedaily.com · Aug 12
Summary
A single fossil clam from Oman indicates Earth had about 372 days per year 70 million years ago, with each day lasting roughly 23.5 hours instead of 24.
Nine years of shell growth layers, sampled with 10-micrometre laser spots, produced a composite estimate of 372 daily laminae per year with an uncertainty of 8.4 days.
The shorter day fits tidal evolution: the Moon's gravity slowed Earth's rotation over time while pushing the Moon outward, now measured at about 3.8 centimetres a year.
Shell chemistry also points to extreme Cretaceous warmth—summer seas near 40C and winters above 30C—and suggests the clam may have grown faster in daylight through photosymbiosis.
Researchers say the bigger advance may be the method itself, which could let other well-preserved shells test or refine deep-time estimates of Earth's rotation.