Three "super Earth" planets have been found orbiting a nearby star at a distance where life in theory could exist, according to a record-breaking tally announced on Tuesday by the European Southern Observatory (ESO).

The three are part of a cluster of as many as seven planets that circle Gliese 667C, one of three stars located a relatively close 22 light years from Earth in the constellation of Scorpio, it said.

China's Shenzhou-10 spacecraft has completed a challenging mission to manually dock with a space module and its three astronauts are expected to return to earth on Wednesday, state media said Tuesday.

The astronauts have completed their mission after docking twice with the Tiangong-1 space module, where they conducted medical experiments and delivered a lecture to schoolchildren, China's official Xinhua news agency said.

New evidence that fracking may contaminate drinking water was published Monday in a study sure to add fuel to the fight over the controversial method of extracting natural gas from cracks in rocks.

Researchers at Duke University analyzed 141 drinking water samples from private water wells across the gas-rich Marcellus shale basin in northeastern Pennsylvania.

Two space station astronauts took care of a little outside maintenance Monday.

Russian flight engineers Fyodor Yurchikhin and Alexander Misurkin replaced a main valve on the International Space Station and prepared for the arrival of a new lab later this year.

Climate change is creating more frequent and more unpredictable extreme weather events, forcing insurers to change how they assess the risk of natural disasters hitting a specific area, the Geneva Association think tank said Monday.

"Traditional approaches, which are solely based on analyzing historical data, increasingly fail to estimate today's hazard probabilities," the think tank for strategically important insurance and risk management issues, warned in a report.

Higher levels of air pollution reduced the frequency of North Atlantic hurricanes and other tropical storms for most of the 20th century, a study said Sunday.

Adding to evidence for mankind's impact on the weather system, the probe found a link between these powerful storms and aerosols, the scientific term for specks of matter suspended in a gas.

Three Chinese astronauts on the country's longest manned space mission on Sunday succeeded in manually docking their spacecraft with a module orbiting Earth, state media said.

Docking techniques are a crucial element of China's space program, which aims to build a station orbiting the planet by 2020.

Singapore woke up to clear blue skies on Monday thanks to favorable winds but Malaysia was still being suffocated by smog from forest fires in Indonesia, where cloud-seeding flights have produced little rain.

Officials in Singapore, which bore the brunt of the smog last week, warned against complacency, saying the situation could deteriorate again if monsoon winds carrying smoke and particulates from Indonesia's Sumatra island changed direction.

Forest fires in Indonesia, which have cloaked Singapore in record-breaking smog, are raging on palm oil plantations owned by Indonesian, Malaysian and Singaporean companies, environmental group Greenpeace said Saturday.

Singapore's worst environmental crisis in more than a decade has seen the acrid smoke creep into people's flats and shroud residential blocks as well as downtown skyscrapers, and the island's prime minister has warned it could last weeks.

Heightened radioactivity levels were found outside a nuclear waste tank in the U.S. state of Washington, officials said Friday, in a new alert about a site used to make Cold War-era bombs.

Governor Jay Inslee said there was no immediate public health threat, but urged federal authorities to accelerate action to deal with leaks at the Hanford site, which he sounded the alarm about four months ago.