What was life like on early Earth? That's a question that many scientists have tackled over the years. Now, though, researchers have announced that when Earth's organisms first formed, it may have been in an ice cold ocean.
Many researchers have thought that Earth's early oceans were very warm, reaching temperatures up to 80 degrees Celsius. New findings, though, suggest that the opposite may have been true. It seems as if Earth's climate may have been very cold instead of very warm.
In this latest study, the researchers analyzed volcanic and sedimentary rocks in South Africa that were deposited at depths of 2 to 4 kilometers. These rocks once formed at latitudes that were comparable with that of the Canary Islands. Surprisingly, the sedimentary rocks showed a remarkable resemblance to those known from more recent ice ages.
But how did the researchers find out the temperature of the ocean from these rocks? They analyzed the relations between oxygen isotopes in rocks known as "chert," which is a rock composed of pure silicium-oxide. These rocks had been exposed to high temperatures, but this was related to hydrothermal activity.
The researchers also looked at finely grained sedimentary rocks that existed along with the deep-submarine volcanic rocks. There, they found gypsum, which is produced under high pressure and at very cold temperatures, as in the present deep ocean.
"In other words, we have found independent lines of evidence that the climate conditions at this time may have been quite similar to the conditions we have today," Harald Furnes, one of the researchers, said.
With that said, Furnes believes that some researchers will have difficulty accepting the idea of a cold, early Earth. However, all current lines of evidence that Furnes and his team have uncovered points in that direction.
The findings reveal a bit more about what Earth was like 3.5 billion years ago. At that time, it's likely that our planet suffered a type of global ice age. Not only that, but it indicates that life may have first formed on a cold planet rather than on a warm one.
The findings are published in the March 2016 journal Science Advances.
