Waist deep in sparkling blue water off the white beaches of the Indian Ocean spice island of Zanzibar, seaweed farmer Mtumwa Vuai Ameir gently ties seedlings to wood poles.

Seaweed farmed on the Tanzanian archipelago is one of Zanzibar's key exports -- used for food, cosmetics and medicines in Asia, Europe and North America -- but now the vital industry is struggling with warmer waters killing the crops.

Large parts of Australia's Great Barrier Reef could be dead within 20 years as climate change drives mass coral bleaching, scientists warned Friday.

The World Heritage-listed reef is currently suffering its worst bleaching in recorded history with 93 percent of corals affected due to warming sea temperatures.

Russia's new Vostochny cosmodrome hosted its first rocket launch Thursday, the Roscosmos space agency said, after a last-minute delay a day earlier led to President Vladimir Putin criticizing the program's officials.

The Soyuz 2.1a rocket carrying three satellites took off at 11.01 am local time (0201 GMT), the national space agency said in a statement, after the countdown was automatically halted for technical reasons 24 hours previously.

Einstein's theory of general relativity is to be put to the test by a newly launched satellite in an experiment that could upend our understanding of physics.

The French "Microscope" orbiter will try to poke a hole in one of Einstein's most famous theories, which provides the basis for our modern understanding of gravity.

Solar Impulse 2, an experimental plane flying around the world without consuming a drop of fuel, landed Sunday in California, one leg closer to completing its trailblazing trip.

"The Pacific is done, my friend. I love it, but it's done," said clearly relieved Swiss adventurer Bertrand Piccard, who piloted from Hawaii to California, just before landing.

China plans to send a rover to Mars to explore the Red Planet, a top space official announced on Friday, in the latest step of its ambitious space program.

Authorities approved the mission in January, said National Space Administration director Xu Dazhe told a press conference in Beijing, according to a transcript.

A huge, five-million-year-old whale tooth has been discovered on an Australian beach, providing the first evidence of the now extinct killer sperm whale outside the Americas.

The 30-centimeter-long (12-inch) fossilized tooth, which is larger than that of a Tyrannosaurus rex, was found by a fossil enthusiast at Beaumaris Bay near Melbourne in February.

What happens when the site of the world's worst nuclear accident is left all but abandoned for nearly 30 years?

In the case of Chernobyl, it becomes a unique chance to see how wildlife recovers in what is a giant nature reserve, bereft of humans but tainted by radiation.

Igor Magala can still remember the metallic taste he got in his mouth as he drove up to the Chernobyl nuclear power station on the morning of April 26, 1986.

The night before, Magala -- the deputy construction boss at the plant -- had received a phone call telling him there had been an accident and summoning him in to help, but he had few other details.

The growth of genetically-modified crops has dipped for the first time following two decades of steady increases, according to a study released Wednesday.

Twenty years after the first genetically-modified plant was marketed, the worldwide acreage of GM crops reached 181.5 million hectares in 2014.