Ancient diamonds hint at Earth’s age

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

Found trapped in zircon crystals, the small gems are the oldest identified fragments of the Earth’s crust and their existence suggests the Earth may havecooled 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,” said Alexander Nemchin, an expert in geochemistry at Australia’s Curtin University of Technology and one of Menneken’s co-researchers. “We’re dealing with the oldest material on the planet.

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

Martin Van Kranendonk, a senior geologist with the Geological Survey of Western Australia, said unravelling 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.

What spider could construct such a massively creepy web?

There are times when you can literally hear the screech of millions of mosquitoes caught in this eerie spider web.

Officials at Lake Tawakoni State Park say the sprawling spider web is a big attraction for some visitors, while others will not go anywhere near it.

Now entomologists are debating the origin and rarity of the web that blankets several trees, shrubs and the ground along a 200-yard (182-metre) stretch of trail in a North Texas park.

The webs bring to mind the terrifyingly large spiders featured in the Harry Potter movies

"At first, it was so white it looked like fairyland," said Donna Garde, superintendent of the park about 45 miles (72 kilometres) east of Dallas. "Now it's filled with so many mosquitoes that it's turned a little brown. There are times you can literally hear the screech of millions of mosquitoes caught in those webs."

Spider experts say the web may have been constructed by social cobweb spiders, which work together, or could be the result of a mass dispersal in which the arachnids spin webs to spread out from one another.

"I've been hearing from entomologists from Ohio, Kansas, British Columbia - all over the place," said Mike Quinn, an invertebrate biologist with the Texas Parks and Wildlife Department who first posted photos online.

Herbert A. "Joe" Pase, a Texas Forest Service entomologist, said the massive web is very unusual. "From what I'm hearing it could be a once-in-a-lifetime event," he said.

But John Jackman, a professor and extension entomologist for Texas A&M University, said he hears reports of similar webs every couple of years.

"There are a lot of folks that don't realise spiders do that," said Jackman, author of "A Field Guide to the Spiders and Scorpions of Texas."

"Until we get some samples sent to us, we really won't know what species of spider we're talking about," Jackman said.

Garde invited the entomologists out to the park to get a firsthand look at the giant web.

"Somebody needs to come out that's an expert. I would love to see some entomology intern come out and study this," she said.

Park rangers said they expect the web to last until fall, when the spiders will start dying off.

Total Lunar Eclipse Visible in U.S.

The Earth's shadow will creep across the moon's surface early Tuesday, slowly eclipsing it and turning it to shades of orange and red.

Aug. 28: The moon glows red during a lunar eclipse seen in Sydney, Australia.

Aug. 28: The moon glows red during a lunar eclipse seen in Sydney, Australia.

The total lunar eclipse, the second this year, will be visible in North and South America, especially in the West. People in the Pacific islands, eastern Asia, Australia and New Zealand also will be able to view it if skies are clear.

People in Europe, Africa or the Middle East, who had the best view of the last total lunar eclipse in March, will not see this one because the moon will have set when the partial eclipse begins at 4:51 a.m. EDT. The full eclipse will begin an hour later at 5:52 a.m. EDT.

An eclipse occurs when Earth passes between the sun and the moon, blocking the sun's light. It is rare because the moon is usually either above or below the plane of Earth's orbit.

Since the Earth is bigger than the moon, the process of the Earth's shadow taking a bigger and bigger "bite" out of the moon, totally eclipsing it before the shadow recedes, lasts about 3 1/2 hours, said Doug Duncan, director of the University of Colorado's Fiske Planetarium. The total eclipse phase, in which the moon has an orange or reddish glow, lasts about 1 1/2 hours.

The full eclipse will be visible across the United States, but East Coast viewers will only have about a half-hour to see it before the sun begins to rise and the moon sets. Skywatchers in the West will get the full show.

In eastern Asia, the moon will rise in various stages of eclipse.

During the full eclipse, the moon will not be completely dark because some light still reaches it around the edges of the Earth. The light is refracted as it passes through our atmosphere, scattering blue light — which is why the sky is blue — but sending reddish light onto the moon.

"When someone asks why is it [the moon] red, you can say because the sky is blue," Duncan said.

The next total lunar eclipse occurs Feb. 21, 2008, and will be visible from the Americas, Europe and Asia.