A new study has found that days were shorter by half an hour during the dinosaur era. According to the study, the Earth turned faster than it does today, rotating 373 times a year, compared to current 365 rotations a year. According to reports, researchers studied fossil mollusk shells from the Late Cretaceous that helped them made the discovery.
According to a press release by AGU, the new study used lasers to sample minute slices of shell and count the growth rings more accurately than human researchers with microscopes. The growth rings allowed the researchers to determine the number of days in a year and more accurately calculate the length of a day 70 million years ago. The new measurement informs models of how the Moon formed and how close to Earth it has been over the 4.5-billion-year history of the Earth-Moon gravitational dance.
Niels de Winter, an analytical geochemist at Vrije Universiteit Brussel and the lead author of the new study said, "We have about four to five data points per day, and this is something that you almost never get in geological history. We can basically look at a day 70 million years ago. It’s pretty amazing."
The new study also found corroborating evidence that the mollusks harboured photosynthetic symbionts that may have fueled reef-building on the scale of modern-day corals. The new study found the composition of the shell changed more over the course of a day than over seasons, or with the cycles of ocean tides. The fine-scale resolution of the daily layers shows the shell grew much faster during the day than at night.
The new study suggest that the ocean temperatures were warmer in the Late Cretaceous, reaching 40 degrees Celcius in summer and exceeding 30 degrees Celcius in winter. The new study analyzed a single individual that lived for over nine years in a shallow seabed in the tropics, a location which is now, 70-million-years later, dry land in the mountains of Oman.