North Pole

Pinhead-sized fossils buried deep under the ocean show that glaciers did not coat the poles 41 million years ago, a new study shows, disputing earlier research that suggested huge ice sheets covered the Earth's extremities.

Any glaciers then   a time when the planet was much warmer  would only have been in small areas in Antarctica's interior and not in the Northern hemisphere, said Paul Wilson, from Britain's National Oceanography Centre, who led the study.

Wilson's study contradicts research published in 2005 that suggested ice sheets covered much of both polar regions, despite the higher temperatures. He added that the fossils could provide clues to the future of climate change.

"Essentially their idea (in the earlier study) was a mistake based on inadequate data," he told  of the previous study before his work appeared in the journal Nature.

Using the world's only ship capable of executing the research operation, Wilson's team drilled deep through sediment layers at the bottom of the Atlantic Ocean near Surinam for the fossils of single-celled animals called foraminifera. It then tested the chemistry of their tiny shells for signs of ice formation.

"The hard thing is getting hold of sediment 40 million years old to generate a record," he said.

In the period his team studied, the earth had about as much carbon dioxide in the atmosphere as scientists predict may be present in 100 years, so the findings also offer clues as to how rising greenhouse gas levels may affect the planet, Wilson said.

"In order to understand where we are headed you need to go a lot farther back in geologic history to encounter conditions we may face in the future," he said.

Greenhouse gases such as carbon dioxide are widely blamed for global warming. Scientists say average temperatures will rise by between 2-6 degrees Celsius (about 4-11 F) by the end of the century, causing droughts, floods and violent storms. North Pole

Diamonds more than 4 billion years old -- nearly as old as the Earth itself -- have been discovered in Western Australia, giving scientists vital clues about the early history of our planet.

Found trapped in zircon crystals in the Jack Hills region, the small gems are the oldest identified fragments of the Earth's crust and their existence suggests the Earth may have cooled faster than previously thought, experts said on Wednesday.

The time between the creation of the Earth around 4.5 billion years ago and the formation of the oldest known rocks some 500 million years later is known as the Hadean period -- the "dark ages" of geology.

Many geologists have traditionally thought of it as a time when the surface of the planet was a mass of molten lava. But the discovery of the ancient diamonds, reported in the journal Nature, challenges that view.

Martina Menneken of Westfalische Wilhelms-Universitat Muenster, Germany, and colleagues said the presence of diamonds -- which are created under intense pressure -- implied there was a relatively thick continental crust as early as 4.25 billion years ago.

This suggests it may have taken only around 200 million years for the Earth's surface to cool enough for water to condense and oceans to form.

"These latest findings indicate that the planet was already cooling and forming a crust much earlier than previously thought," Alexander Nemchin, an expert in geochemistry at Australia's Curtin University of Technology and one of Menneken's co-researchers, said in a statement.

"Jack Hills is the only place on Earth that can give us this kind of information about the formation of the Earth. We're dealing with the oldest material on the planet."

Radioactive dating showed the crystals from Western Australia varied in age from 3.06 billion to 4.25 billion years, making them almost 1 billion years older than the previous oldest-known diamonds.

Martin Van Kranendonk, a senior geologist with the Geological Survey of Western Australia, said unraveling the history of the crystals was a boon for researchers.

"Any information about the very early Earth is fantastic, it's like a Christmas present for geoscientists," he said.