Scientists have identified nanostructures in the ultra-black skin markings of an African viper which they said Thursday could inspire the quest to create the ultimate light-absorbing material.

The West African Gaboon viper, one of the largest in Africa and a master of camouflage, has dark spots in the geometrical pattern of its skin that are deep, velvety black and reflect very little light.

Russian explorers headed home Thursday after proving it is possible to drive from Russia to Canada across the North Pole, in buses with bloated tires over drifting ice, using a pickaxe to clear the way.

Their two-and-a-half-month hitherto untried odyssey aimed to road test the hand-crafted vehicles on ice and water, conduct a few scientific experiments, and bring together a band of adventurers drawn to the vast and pristine Arctic, expedition leader Vassili Ielaguine said during a stopover in Ottawa.

Water from the world's shrinking glaciers was responsible for almost a third of the rise in sea levels between 2003 and 2009, new research showed Thursday.

A study published in the journal Science revealed that researchers had analyzed data gleaned from two NASA satellites as well as traditional ground measurements from glaciers around the world.

A thud, dirt in the window of his capsule and the fresh smell of spring on the Kazakh steppe: Canadian astronaut Chris Hadfield recalled Thursday his safe return from a five-month mission to space.

"We hit the Earth just like a car crash," Hadfield told a webcast news conference from NASA headquarters in Houston, Texas, where he has been undergoing tests and readapting to gravity since Tuesday's landing.

NASA's planet-hunting Kepler spacecraft appears to be hobbled by a faulty wheel and may be near the end of its four-year mission, space agency scientists said Wednesday.

Kepler, a $600 million mission, was launched in 2009 on a search for other planets. So far, it has found 2,700 candidates, including a handful that may be habitable worlds, not too hot and not too cold.

A review of thousands of studies published over 21 years found "overwhelming" and growing consensus among scientists that humans are mostly to blame for global warming, its authors said Thursday.

This contradicts a widely held view that scientists are deeply divided on the topic -- a misconception that complicates efforts to win public backing for climate policy, the authors wrote in the journal Environmental Research Letters.

Australia said it was pushing for a ban Thursday of any commercial use of a pioneering technique to reduce the impacts of climate change by "fertilizing" the world's oceans with iron, warning of significant risks.

Environment Minister Tony Burke said Australia had worked with Nigeria and South Korea on an amendment to the London Protocol governing waste dumping at sea which would prohibit commercial fertilization activities.

Ghanaian college students plan Wednesday to launch a model of a satellite the size of a Coke can 200 yards (meters) into the air.

Organizers hope that it will be the start of this West African country's space program.

Scientists said Tuesday they have found a way to extract gold from ore using a seemingly unlikely pantry item -- cornstarch.

Traditional leaching employs poisonous cyanide to dissolve and extract the gold locked up in mineral ore -- but the method is polluting and controversial.

Researchers trying to explain declining elk numbers in the Yellowstone National Park (YNP) placed part of the blame Wednesday on a previously unlinked phenomenon -- a predatory trout invasion.

In a vicious circle of human interference that underscores the delicate balance of nature, the team said the illegal introduction of lake trout more than 20 years ago changed the diet of a key Yellowstone predator -- the grizzly bear.