A note that Albert Einstein gave to a courier in Tokyo, briefly describing his theory on happy living, has surfaced after 95 years and is up for auction in Jerusalem.

Lake Baikal is undergoing its gravest crisis in recent history, experts say, as the government bans the catching of a signature fish that has lived in the world's deepest lake for centuries but is now under threat.

Holding one-fifth of the world's unfrozen fresh water, Baikal in Russia's Siberia is a natural wonder of "exceptional value to evolutionary science" meriting its listing as a World Heritage Site by UNESCO.

Scientists have for the first time witnessed the crash of two ultra-dense neutron stars, cataclysmic events now known to have generated at least half the gold in the Universe, excited research teams revealed Monday.

Shockwaves and light flashes emitted by the cosmic fireball traveled some 130 million light-years to be captured by Earthly detectors on August 17, they revealed at simultaneous press conferences around the globe as a dozen science papers were published in top academic journals.

Russia on Friday launched a European satellite dedicated to monitoring the Earth's atmosphere, the protective layer that shields the planet from the sun's radiation, live footage from the cosmodrome showed.

Two U.S. astronauts have installed a high-definition video camera at the International Space Station and made more progress on repairs to the lab's robotic arm, NASA said.

NASA spokesman Rob Navias described the camera equipment as offering "new eyes" to the orbiting outpost, as live video showed astronaut Randy Bresnik in sharp detail, floating in his white spacesuit.

Two NASA astronauts wrapped up a successful spacewalk Thursday to repair the International Space Station's aging robotic arm, the U.S. space agency said.

The outing by Americans Randy Bresnik and Mark Vande Hei ended at 3 pm (1900 GMT), marking a "very successful day," a NASA spokesman said.

U.S. astrophysicists Barry Barish, Kip Thorne and Rainer Weiss were awarded the Nobel Physics Prize on Tuesday for the discovery of gravitational waves, the Nobel jury said.

An Ariane 5 rocket put two commercial satellites into orbit after an initial attempt was aborted earlier this month, operator Arianespace said early Saturday.

A reusable, water-powered Mars lander that will allow humans to explore the Red Planet from an orbiting 'base camp' as early as the 2030s was unveiled Friday by US defence giant Lockheed Martin.

Governments and private firms are collaborating on projects to send humans to new frontiers, with NASA planning missions next decade into the space between Earth and the Moon to prepare for trips to Mars.

Iran's on-off space programme has received a boost after a recent satellite launch was seen to annoy Washington, with Tehran dusting off plans for a manned mission, perhaps with Moscow's assistance.