A northern white rhinoceros -- one of just four remaining worldwide -- died Sunday at the San Diego Zoo, officials said.

The 41-year-old female known as Nola saw her health take a quick turn for the worse.

In fact, countries are at such odds over whether to do away with the "leap second" -- an extra second periodically added to compensate for irregularities in the earth's rotation around the sun -- that they have put off deciding the matter until 2023, the United Nations announced Thursday.

Country representatives gathered for a conference in Geneva hosted by the UN's International Telecommunication Union (ITU) have been haggling over the issue since the beginning of the month without reaching agreement.

In the middle of a desiccated lake bed in South Africa's North West province, a seven-month-old calf is too weak to get up. It is doomed to die from thirst and hunger.

A devastating drought is claiming thousands of livestock in Africa's most developed economy and prompting many to fear famine.

Since it awoke in August from a 138-year slumber, Ecuador's Cotopaxi volcano has become one of the most-watched in the world, holding wary locals and fascinated scientists in thrall.

Cotopaxi, whose snowy peak rises majestically from the patchwork quilt of central Ecuador's high plains, rumbled to life on August 14, belching a column of ash in its first major eruption since 1877.

French astronaut Thomas Pesquet will carry the text of any climate change deal clinched in Paris in December into space with him next year, a French junior minister for research said on Thursday.

"We truly hope to be able to give you the text of the final resolution," Thierry Mandon told a news conference in Paris, adding that he was still hopeful of an agreement next month despite "much uncertainty" surrounding the talks.

A chimpanzee mother cared for her disabled infant in the wild in Tanzania, Japanese researchers reported in a study published this week, research they hope will help in understanding the evolution of social care in humans.

A team of Kyoto University researchers discovered that a "severely disabled" female chimpanzee baby was born in a group in Tanzania's Mahale Mountains National Park in 2011, and recorded behavior of the group for about two years.

A year ago on Thursday, the world held its collective breath as a European spacecraft dropped a tiny robot lab onto the surface of a comet hurtling towards the Sun.

The 12 months since that bumpy landing have yielded many exciting scientific finds, and more than a little drama, as Philae intermittently phoned home from its alien host between long bouts of sleep.

Two U.S. astronauts stepped out on a risky spacewalk Friday to complete the repair of an ammonia cooling system at the International Space Station.

Highly toxic ammonia is used to cool electronics at the orbiting outpost, and the thermal system has been plagued by problems.

A drought caused by the El Nino weather phenomenon is worrying farmers in the Colombian Andes who fear for their crop -- one of the world's most prized coffee beans.

"The harvest is about to be lost. We farmers are in total despair," said Raul Fajardo, 56, who grows coffee beans at 1,800 meters (5,900 feet) altitude on the slopes of the Galeras volcano.

A third of China's forests are under threat despite the Communist Party announcing a ban on commercial logging in natural forest, activists said Wednesday.

Vast swathes of woodlands have been destroyed during China's decades-long economic boom, but environmental concerns are rising up the agenda and the measure was included in guidelines the ruling party issued for the country's next five-year plan.