The asteroid that smashed into the central Russian city of Chelyabinsk initially measured 19 meters (61 feet) across, packing the energy of dozens of Hiroshima bombs, a study said on Wednesday.

Scientists in the Czech Republic and Canada analysed video and audio footage and fragments recovered from the dramatic incident on February 15.

Chinese scientists have discovered the oldest known fossil of a pair of insects caught in the act of copulating, according to a study released Wednesday.

The imprint of the male and female froghoppers, lying belly to belly, was dug up in northeastern China. The fossil is believed to be 165 million years old, said the report in the journal PLOS ONE.

Paleontologists on Wednesday unveiled a new dinosaur discovered in the U.S. that proves giant tyrant dinosaurs like the Tyrannosaurus rex were around 10 million years earlier than previously believed.

A full skeletal replica of the carnivore — the equivalent of the great uncle of the T. rex — was on display at the Natural History Museum of Utah alongside a 3-D model of the head and a large painted mural of the dinosaur roaming a shoreline.

The world's first robot astronaut is pining for a conversation partner as he waits for Japanese spaceman Koichi Wakata aboard the International Space Station.

"Mr. Wakata, are you not here yet? I really want to see you soon," the pint-sized android said in a message released by its project team in Japan Wednesday.

Decomposed whale carcasses have been washing up on beaches in Ghana's oil-producing west, raising the ire of environmental groups worried the country's growing petroleum industry may be killing marine life.

A total of 20 dead whales have been discovered along Ghana's coastline in the last four years, including at least eight since September.

The amount of greenhouse gases in Earth's atmosphere hit a new record high in 2012, continuing an ever-faster rise that is driving climate change, the U.N. weather agency said Wednesday.

"The concentrations are reaching once again record levels," Michel Jarraud, who heads the World Meteorological Organization (WMO), told reporters in Geneva.

Researchers studying the effects of climate change on polar bears are experimenting with the idea of crowdsourcing data as improving technology allows anybody with an Internet connection to monitor the animals' annual migration in Canada.

Polar bears gather at this time of year on the Hudson Bay's southwestern shore to wait for the water to freeze so they can wander the ice and hunt for seals. The migration to the Wapusk National Park in Manitoba is far enough south to make the Western Hudson Bay polar bears one of the most accessible and studied populations of the species.

A giant extinct species of the platypus with powerful teeth has been discovered in Australia, with a scientist on Tuesday describing the duck-billed water animal as a Godzilla-like monster.

The new species, named Obdurodon tharalkooschild, was identified by a single but highly distinctive tooth found in the Riversleigh site in the northeastern Australian state of Queensland -- a World Heritage area rich in fossil deposits.

As many as one in five Sun-like stars may have a planet the size of Earth, and the nearest could be in systems visible to the naked eye, US astronomers said Monday.

The research is based on a new analysis of findings from NASA's Kepler space observatory, and appears in the Proceedings of the National Academy of Sciences.

India successfully launched its first mission to Mars on Tuesday, aiming to become the only Asian nation to reach the Red Planet with a program showcasing its low-cost space technology.

"It's lift off," said a commentator on state television as the red-and-black rocket blasted into a slightly overcast sky on schedule at 02:38 pm (0908 GMT) from the southern spaceport in Sriharikota.