Making Unique Observations in a Very Cluttered World

Monday, 24 February 2014

Tiny Crystal Is Oldest Known Piece of Earth, Scientists Say - dating to 4.4 Billion years -

Tiny Crystal Is Oldest Known Piece of Earth, Scientists Say - dating to 4.4 Billion years - 

Image: A 4.4 billion-year-old zircon crystal from the Jack Hills region of Australia is pictured in this handout photo

Scientists using two different age-determining techniques have shown that a tiny zircon crystal found on a sheep ranch in western Australia is the oldest known piece of our planet, dating to 4.4 billion years ago.

Writing in the journal Nature Geoscience on Sunday, the researchers said the discovery indicates that Earth's crust formed relatively soon after the planet formed and that the little gem was a remnant of it.

John Valley, a University of Wisconsin geoscience professor who led the research, said the findings suggest that the early Earth was not as harsh a place as many scientists have thought.

To determine the age of the zircon fragment, the scientists first used a widely accepted dating technique based on determining the radioactive decay of uranium to lead in a mineral sample.

But because some scientists hypothesized that this technique might give a false date due to possible movement of lead atoms within the crystal over time, the researchers turned to a second sophisticated method to verify the finding.

They used a technique known as atom-probe tomography that was able to identify individual atoms of lead in the crystal and determine their mass, and confirmed that the zircon was indeed 4.4 billion years old.

To put that age in perspective, the Earth itself formed 4.5 billion years ago as a ball of molten rock, meaning that its crust formed relatively soon thereafter, 100 million years later. The age of the crystal also means that the crust appeared just 160 million years after the very formation of the solar system.

The finding supports the notion of a "cool early Earth" where temperatures were low enough to sustain oceans, and perhaps life, earlier than previously thought, Valley said.

The zircon was extracted in 2001 from a rock outcrop in Australia's Jack Hills region. For a rock of such importance, it is rather small. It measures only about 200 by 400 microns, about twice the diameter of a human hair.


China's Naval Chief Says Smog is Best Defence Against US Laser Weapons... -

China's Naval Chief Says Smog is Best Defence Against US Laser Weapons... - 

Thick smog is the best defence against US laser weapons, a Chinese military chief has declared on national television.

Zhang Zhaozhong, the Navy Major General for the People's Liberation Army drew massive criticism when he made the statement on CCTV's Haixia Liang'an (Cross-Straits) current affairs programme, adding that lasers were "most afraid of smog".

He said: "Under conditions where there is no smog, a laser weapon can fire [at a range of] 10 kilometres. When there's smog, it's only one kilometre. What's the point of making this kind of weapon?

"It only works when the weather is good. The enemy will target you when the weather is bad.

"Once your enemy knows your disadvantages you are dead. This is a laser weapons' fatal disadvantage."

Zhang explained that smog was made up of tiny metallic particulate, known as PM2.5, and the higher its concentration the harder it is for lasers to get through.

He was speaking after the US navy announced it was preparing to deploy its first laser weapon aboard transport ship, USS Ponce, which is aimed at protecting US forces in the Persian Gulf.

But thousands of people took to social media site Sina Weibo to criticise Zhang's comments.

In response the major general said his statements were taken out of context and led to "misunderstanding".

He told Beijing Youth Daily: "I just stated a laser weapon's weakness. I don't support smog."

According to the World Health Organisation the presence of tiny pollution particles should not exceed 25 micrograms per cubic metre. In Beijing levels were recorded at almost 400.

Read more -