Smithsonian.com

A playa (at least outside of the young urban vernacular) is a dry lake bed. The 2.5-mile “Racetrack Playa” on the west side of Death Valley National Park, in California, is famous for its mysterious sliding rocks.

In the 100 years since these large (about a foot tall and as much as several hundred pounds) sliding rocks were first noticed, apparently nobody has actually ever seen them move. They see only the long trails marked out in the cracked surface of the lake bed.

So why do they move? It’s not gravity: The playa is extremely flat. Geologists’ strongest hypothesis points to rain. Though the region is extremely dry, when it does rain, the silt and clay surface turns into a muddy Slip-N-Slide. Then, a strong gust of wind—up to 70 mph—can get the rock moving, and once in motion, slower winds can keep it going. The rocks change direction, the theory goes, with the wind.

(Hat tip to Alex B., who passed along this article from Geology.com)

(Photo by Flickr user TravOC)

Well, on Friday morning it was snowing at McMurdo Station, and the pilots scrubbed our flight down to Antarctica. It being Thanksgiving, the station had Saturday and Sunday off. It seemed we were not destined to become polar explorers on this particular weekend.

So we hightailed it to 12,300-foot, stupendously scenic Mt. Cook (which the Maori call Aoraki), New Zealand’s highest point. Here I ran across the kea, a famously mischievous parrot that lives only in the New Zealand mountains, up near treeline.

I had hiked up an incredibly steep trail set against blue-white glaciers that crowded the slopes of Mt. Sefton just across the valley. Aoraki itself loomed at the end of another valley, a cold white cloud streaming off its peak. My hillside was covered with grassy tussocks, strange, stunted trees, and rocks of gray, black and red.

Into this scene floated a green-and-brown parrot calling “kee-aaaâ€? in a reedy voice. It landed on a boulder, flashing red underneath the wings, then sidled down the rock and into a treetop to pick at foliage. These birds are renowned for being smart enough to get into trouble: they eat windshield wiper blades in parking lots, break into campers’ tents, and figure out how to raid tins of biscuits. Some have even learned the macabre habit of feeding on sheep.

By coincidence, the next person I ran into on the trail was Gyula Gajdon, a postdoctoral scholar at the University of Vienna who studies keas. He and an assistant were just beginning a project to track young keas after they leave the nest. Other aspects of his research investigate how the parrots share new skills by watching each other. It’s an ability called “cultural learningâ€? – something you attempt every time someone shows you a card trick and you say “Hey – how’d you do that?â€?

Hugh will be posting from Antarctica through late December. Follow his adventures at Polar Discovery.

German scientists recently unearthed the fossilized claw of an 390 million-year-old sea scorpion. The finding was, literally, huge: the claw was 18.1 inches long, making the beast that used it longer than 8 feet!

The scientist who actually found the claw, Markus Poschmann of the Mainz Museum in Germany, describes what happened when he was excavating a quarry in Prüm, Germany:

I was loosening pieces of rock with a hammer and chisel when I suddenly realised there was a dark patch of organic matter on a freshly removed slab. After some cleaning I could identify this as a small part of a large claw. Although I did not know if it was more complete or not, I decided to try and get it out.

The fossil analysis, published last week in the journal Biology Letters, identified the claw as sea scorpion Jaekelopterus rhenaniae, an extinct species that gave rise to modern scorpions and possibly all arachnids.

I’ll leave you with an intriguing question about the scorpion posed by a reader on Carl Zimmer’s blog, The Loom: “Would it taste like lobster?”

(Above, an Egyptian deathstalker scorpion, Leiurus quinquestriatus, under blacklight. Flickr, by furryscaly)

Unfazed by NASA’s snazzy imagery, the European Space Agency recently rolled out some glossy black photos of its own: the Earth at night, as seen by the Rosetta spacecraft some 75,000 kilometers above the Indian Ocean, just last Tuesday.

I’ve seen Earth-at-night posters before, but I particularly like this one, because it’s an entire hemisphere, and because of the blazing crescent, reminiscent of a new moon, that’s visible in the south. Look closely and you can make out parts of Africa, India and Asia, as well as marvel at the inky blackness of the Southern Hemisphere.

Images of the Earth are small potatoes for the unmanned Rosetta. Its day job–which it won’t start until 2014, after a ten-year commute–is to catch up to a distant comet and then send out an automated landing craft to touch down on the surface. To build up enough speed to get there on time, Rosetta is doing two separate slingshot-around-Earth maneuvers, aided by a slingshot around Mars, before hurtling out through the asteroid belt toward comet Churyumov-Geramisenko, more than 30 million kilometers away.

But just before Rosetta departs Earth forever, take another look at that illuminated crescent. That’s the 24-hour daylight of the Antarctic summer bleeding through onto the dark side of the Earth. And for the next six weeks, it’s going to be my home. Along with several National Science Foundation-sponsored scientists, I’ll be sleeping in tents, camping at penguin colonies and sampling lava flows on a dormant volcano. Also, drinking lots of instant soup. I’ll be posting regular updates to The Gist whenever I reach an Internet connection.

That’s assuming I ever see my luggage again. Stay tuned.

(Posted from Christchurch, New Zealand. Image: European Space Agency.)

On Friday, a 30-kilowatt refrigeration system began cooling the Svalbard Global Seed Bank, the Norwegian concrete vault that was designed to protect 4.5 million of the world’s seeds from global calamity.

Unlike the world’s 1,400 smaller seed banks, Svalbard’s is meant to withstand anything—typhoons, plant epidemics, climate change, even economic depressions and war. It’s buried some 400 feet deep inside a mountain, on an island 300 miles from Norway’s mainland. (You can feel Svalbard’s chilly isolation in the above photo, no?)

Already a chilly 23 degrees Fahrenheit, researchers say that, in the next two months of cooling, it will get down to 0 degrees. With temps that low, they say, the seeds will be safe for up to 1,000 years.

The vault is scheduled to open on February 26.

(Flickr, by stiangd)