Million years ago days were half-hour shorter #40040

  • Million years ago days were half-hour shorter #40040

Million years ago days were half-hour shorter #40040

The Earth rotated faster back at the end of the dinosaurs period than it does currently, rotating 372 times per year, while now it only completes orbits of 365 days, as per new research of fossil mollusk shells dating back to the late Cretaceous period. This suggests a day lasted only 23 and a half hours.

Finding more geological records that let us calculate the length of days at different points in Earth's history would help us to plot the Moon's acceleration more precisely; in turn, then we could find out when our Moon formed.

The shell - of an extinct group of mollusc known as the rudist bivalves - had a rapid growth rate that allowed it to preserve a detailed record of the past. Looking at samples of the specimen through a microscope, the researchers were able to see the daily growths, which measured 40 nanometres wide.

The new research also discovered supporting evidence that the mollusks hosted photosynthetic symbionts that may have powered reef-developing on the level of modern-day corals.

"We have about four to five data points per day, and this is something that you nearly never get in geological history", explained geochemist Niels de Winter of Vrije Universiteit Brussel in Belgium. We can necessarily take a gander at a day 70 million years back. "It's pretty wonderful", said Niels de Winter, an analytical geochemist at Vrije Universiteit Brussel and the lead author of the new study. The summer high temperatures likely approached the physiological limits for mollusks, de Winter said.

The new research investigated a single organism that lived for more than nine years in a shallow seabed in the tropics, a place which is now a dry land in the mountains of Oman. They thrived in water several degrees warmer worldwide than modern oceans. That is, before the creatures died out during the Cretaceous-Paleogene extinction event that killed non-avian dinosaurs 66 million years ago.

The specialists state that while cosmic models have anticipated that days 70 million years back were shorter than they are now, this is the most precise computation of to what extent a year would have been during the late Cretaceous.

"There's nothing like it living today", said de Winter. The study also revealed that the shell rings grew more quickly during the day.

There's not at all like it living today, said de Winter. Examples in the rings propose the shells became quicker in the day than around evening time and was driven by sun oriented (as opposed to lunar) cycles.

Scientists writing in Paleoceanography and Paleoclimatology worked this out by analyzing daily growth rings in ancient mollusks.

This suggests that rather than just filtering food from the water like modern oysters - a process that is not dependent on the time of the day - Torreites sanchezi likely harboured symbiotes that fed on sunlight, like modern giant clams.

"Until now, all published arguments for photosymbiosis in rudists have been essentially speculative, based on merely suggestive morphological traits, and in some cases were demonstrably erroneous", explained Peter Skelton, a retired paleontologist from The Open University, in a press release.

'This paper is the first to provide convincing evidence in favour of the hypothesis'.

A day on Earth was only 23.5 hours, 70 million years ago. This was not a surprise, because scientists know days were shorter in the past. That's because the Moon is moving away from Earth at a rate of about 3.8 cm (1.5 in) per year, and the changing tidal forces are slowing down the speed of the Earth's rotation. Just as tree rings contain information about the year in which they grew, those shell rings can be analysed, too.

Clearly, many questions remain about the Earth-Moon relationship, how it's changed over time, and the celestial dynamics that continue to dictate this gravitational union.

At the same time, the Moon is slowly separating itself from Earth each year. The result is precise now available for the late Cretaceous and could be used to model the evolution of the Earth-Moon system. So the Moon's rate of retreat has changed over time, and information from the past, like a year in the life of an ancient clam, helps researchers reconstruct that history and model of the formation of the moon.