A cave discovered near the source of Indonesia's massive earthquake-spawned tsunami contains the footprints of past gigantic waves dating up to 7,500 years ago, a rare natural record that suggests the next disaster could be centuries away — or perhaps only decades.

The findings provide the longest and most detailed timeline for tsunamis that have occurred off the far western tip of Sumatra island in Aceh province. That's where 100-foot (30-meter) waves triggered by a magnitude-9.1 earthquake on Dec. 26, 2004, killed 230,000 people in several countries, more than half of them in Indonesia.

Two American astronauts prepared to step out Tuesday on a rare Christmas Eve spacewalk to wrap up repairs to the cooling system at the International Space Station, NASA said.

The spacewalk is set to begin at 7:10 am (1210 GMT), marking the second outing to replace an ammonia pump module whose internal control valve failed December 11.

Another Chinese city has capped the total number of car licence plates it will issue annually, state media said Sunday, following moves by Beijing and other metropolises to curb pollution and congestion.

The world's most populous nation is also the world's largest car-buyer. But it is trying to curb poor air quality and other environmental damages caused by rapid development.

A vast store of water equivalent in area to Ireland lies beneath Greenland's icesheet, and it may provide answers to one of the big riddles of climate change, scientists reported on Sunday.

In 2011, U.S. scientists crossed the southern Greenland icesheet on an expedition to drill ice cores, a benchmark of annual snowfall.

A Chinese rocket launched Bolivia's first telecommunications satellite early Saturday with the president of the South American country declaring it a success.

The Long March-3B carrier rocket blasted off from the Xichang satellite launch center in China's southwestern Sichuan province at 00:42 am (1640 GMT Friday), television images showed.

Two U.S. astronauts on Saturday stepped outside the International Space Station for the first of three spacewalks to fix a broken equipment cooling system, NASA said.

"Today's spacewalk has officially begun," said a NASA commentator as the space agency broadcast live images of Japanese astronaut Koichi Wakata leading the operation from inside the space station.

Anti-whaling nations including the United States on Friday warned environmentalists and Japanese whalers against taking action that endangers human life as an annual confrontation brews in the remote Southern Ocean.

Australia, the Netherlands, New Zealand and the United States said in a joint statement that they respected the right to protest on the high seas, provided it was non-violent and conducted safely.

File photo of Tibetans passing the Potala Palace in the capital Lhasa, where pollution levels have reached new heights, shrouding the city in dust and halting flights

China's pollution reached new heights on Friday, as the Tibetan capital of Lhasa was shrouded in a cloud of dust that halted flights and rendered one of its most-recognizable landmarks nearly invisible.

Two Australian explorers have battled dangerous sea ice to reach the historic Mawson's Huts in Antarctica which have been isolated for years by a giant iceberg blocking the route in, officials said Friday.

The huts, in the eastern sector of the Australian Antarctic Territory, some 3,000 kilometers south of Hobart, were erected and occupied by the Australian Antarctic Expedition of 1911-1914 led by explorer Sir Douglas Mawson.

The European Space Agency has launched a satellite that it hopes will produce the most accurate three-dimensional map of our part of the Milky Way galaxy.

The agency says its Gaia satellite was lifted into space aboard a Russian-made Soyuz carrier system from French Guiana at 6:12 a.m. (0912 GMT; 4:12 a.m. EST) Thursday.