Planet Earth could be at higher risk of a space rock impact than widely thought, according to astronomers who suggested Tuesday keeping a closer eye on distant giant comets.

Most studies of potential Earth-smashers focus on objects in the asteroid belt roughly between Mars, Earth's outside neighbor, and Jupiter on its other flank, said the researchers.

SpaceX successfully landed its powerful Falcon 9 rocket in an upright position on Monday, a historic first in the company's bid to make rockets as reusable as airplanes.

"The Falcon has landed," a commentator said above the screams and cheers of people gathered at SpaceX headquarters in Hawthorne, California.

Australian scientists Tuesday hailed the discovery of two sea snake species feared to have become extinct years ago off the Western Australia coast.

The short-nose sea snake and the leaf-scaled sea snake had not been seen since disappearing from their only known habitat on Ashmore Reef in the Timor Sea more than 15 years ago, James Cook University researchers wrote in the Biological Conservation journal.

Two American astronauts will step out on a short spacewalk Monday to move a stalled rail car that is stuck outside the International Space Station, NASA said.

Commander Scott Kelly and Flight Engineer Tim Kopra will float out of the orbiting lab to move the mobile transporter rail car "a few inches," NASA said in a statement on Sunday.

SpaceX on Sunday counted down to its first rocket launch since an explosion after liftoff destroyed its unmanned Dragon cargo ship bound for the International Space Station six months ago.

The Falcon 9 rocket is poised to launch at 8:29 pm (0129 GMT Monday) from Cape Canaveral, Florida, announced the California-based company headed by Internet tycoon Elon Musk.

A razor-wire fence rolled out by Slovenia on Croatia's border to block the path of migrants is seriously threatening wildlife in the area, conservation group WWF warned Friday.

The group's statement came a day after Croatia wrote to the European Union saying Slovenia's fence, erected along 137 kilometers (85 miles) of the frontier, presented an "insurmountable obstacle" to the migration of wild animals. 

The Australian government is seeking corporate sponsorship for the Great Barrier Reef, sparking fears Wednesday that companies could potentially use such investments to hide poor green credentials.

The world's biggest coral reef has been under increasing threat from climate change, farming run-off, development and the coral-eating crown-of-thorns starfish.

Tim Peake, the first Briton to travel to the International Space Station, blasted off on Tuesday from the Baikonur cosmodrome with Russian space veteran Yury Malenchenko and Tim Kopra of NASA for a six-month mission.

Fire from the boosters of the Soyuz TMA-19M rocket cut a bright light through the overcast sky at the Russia-operated cosmodrome in Kazakhstan, after the spacecraft launched on schedule at 1103 GMT (17.03 pm local time), according to live television broadcasts.

A Cyprus lawmaker has stirred controversy online after posting a picture of himself at a table serving a dish of songbirds whose poaching is banned on the Mediterranean island.

Evgenios Hamboullas -- a member of the environment committee in the house of representatives -- uploaded the image to Facebook on Saturday with the catchline: "Soon in our restaurants! Happy Holidays!"

A Japanese space probe successfully entered "target orbit" and is on its way to rendezvousing with a far away asteroid, in a quest to study the origin of the solar system, authorities said Monday.

Earlier this month the unmanned explorer, Hayabusa 2, passed by Earth to harness the planet's gravitational pull in a bid to switch its orbital path to continue toward tiny Ryugu asteroid.