GeoEye satellite image

This half-meter resolution image shows icefields near Adelaide Island (on the west), lying at the north side of Marguerite Bay off the west coast of the Antarctic Peninsula. GeoEye tasked its GeoEye-1 satellite to collect this image on April 18.

For commercial imaging satellites, every day is Earth Day: In honor of today's eco-conscious holiday, GeoEye is releasing four recent snapshots of the planet, taken by the company's GeoEye-1 satellite as it orbited 423 miles (681 kilometers) above.

Earth Day isn't just a day for pretty pictures. It's also an occasion to reflect on the state of the planet. This picture of broken-up icefields near Adelaide Island, off the coast of the Antarctic Peninsula, is a reminder that our planet's changing climate is a continuing cause of concern. The Antarctic Peninsula is considered one of the world's fastest-warming "hotspots," as documented by imagery from Europe's Envisat satellite.

"Ice shelves are sensitive to atmospheric warming and to changes in ocean currents and temperatures," Helmut Rott, a professor from the University of Innsbruck in Austria, explained in a statement issued earlier this month. "The northern Antarctic Peninsula has been subject to atmospheric warming of about 2.5 degrees Celsius [4.5 degrees Fahrenheit] over the last 50 years —a much stronger warming trend than on global average, causing retreat and disintegration of ice shelves."

Antarctica's situation serves as a "canary in the coal mine" for the effects of global climate change and the greenhouse-gas effect, to which industrial activity is an increasing contributor. But this isn't just an issue for penguins around the South Pole, or polar bears around the North Pole. Opinion surveys indicate that the public is increasingly seeing a connection between global changes in climate and the way weather works in their own region.

For more about the Antarctic Peninsula in particular, check out this report about the effect of climate change on penguin breeding patterns, this one about concerns for seal pups, this one about the encroachment of invasive species, and this video from 2007 about the continent's shrinking "cathedral of ice." Msnbc.com's Environment section has complete coverage of today's Earth Day goings-on.

Where in the Cosmos
GeoEye's picture of the Antarctic Peninsula was the subject of our latest "Where in the Cosmos" picture puzzle, posted to the Cosmic Log Facebook page. Stacy Thompson Layman was the Cosmic Log correspondent who first came up with the location shown in the picture (after a few hints), and to reward her late-night effort, I'm sending her a pair of 3-D glasses and a copy of "The World in 2050: Four Forces Shaping Civilization's Northern Future," which makes for relevant reading on Earth Day. To get in on future "Where in the Cosmos" puzzle contests, be sure to click the "like" button for Cosmic Log. Here are the three other GeoEye-1 snapshots:

GeoEye satellite image

A curl of land at the tip of Australia's Towra Point Nature Reserve, located on the southern shores of Botany Bay, looks a bit like an elephant and its trunk. A boat speeds through the bay at upper left. Situated on an ancient river delta deposit, the Towra Point reserve is designated as a wetland of international importance because it is a breeding ground and home to many vulnerable, protected or endangered species with diverse habitats. There is also a Towra Point Aquatic Nature Reserve in the surrounding waterways. GeoEye tasked its GeoEye-1 satellite to collect this image on Feb. 19.

GeoEye satellite image

This GeoEye satellite image shows a portion of the D. Ering Wildlife Sanctuary off the Siang River, directly above the Dibru-Saikhowa National Park, located about 7.5 miles (12 kilometers) north of Tinsukia, Assam, India. The sanctuary is named after the late legendary social reformer Daying Ering. The sanctuary consists of a series of islands in the Siang River that are home to endangered animals and many migratory birds. GeoEye tasked its GeoEye-1 satellite to collect this image on March 17.

GeoEye satellite image

This half-meter resolution image shows the Okavango Delta (or Okavango Swamp), located in Botswana in central southern Africa. The Okavango is the world's largest inland delta and formed where the Okavango River empties onto a swamp and into a basin in the Kalahari Desert. Most of the water is lost to evaporation and transpiration instead of draining into the sea. Botswana is one of the world's most ecologically sensitive areas. The Moremi Game Reserve spreads across the eastern side of the delta. GeoEye tasked its GeoEye-1 satellite to collect this image on April 12.

More views of Earth from space:

• Slideshow: Earth as Art 2010
• See the world from the space station
• Slideshow: How astronauts saw Earth
• Holiday calendar 2011: Earth from space

DigitalGlobe

An image from DigitalGlobe's WorldView 1 satellite shows Russia's Vostok Station in Antarctica, the site of a drilling operation that has just reached a subglacial freshwater lake. Lake Vostok may have lain undisturbed for 20 millions of years more than two miles beneath the surface, and thus could harbor living organisms unlike anything scientists have ever seen. The picture was taken on Feb. 8 from an altitude of 308 miles (496 kilometers).

The Russians say that drilling down to a 20 million-year-old lake in Antarctica, more than two miles beneath the surface, is the equivalent of putting an astronaut on the moon. If that's the case, this satellite photo from DigitalGlobe is the equivalent of watching Neil Armstrong and Buzz Aldrin at work.

The photo of Russia's Vostok Station was taken on Wednesday, just a couple of days after Russian researchers reached Lake Vostok in a delicate drilling operation that's been in the works since 1989. Scientists believe the gigantic subglacial reservoir may contain microbes or other organisms unlike any we've seen so far. The achievement also sets the stage for even more ambitious drilling projects that could take place someday on Europa, an ice-covered moon of Jupiter; or on Enceladus, a frozen Saturnian moon that spews forth geysers of water ice. Both those moons are thought to harbor huge subsurface oceans — and perhaps life as well.

The technological challenges involved in the drilling project, as well as the long-term implications raised by studying Lake Vostok, led the head of Russia's Arctic and Antarctic Research Institute, Valery Lukin, to say that "it's fair to compare this project to flying to the moon."

When the folks at DigitalGlobe's analysis group heard the news from Vostok Station, they checked into whether one of their three satellite eyes in the sky got a good look at the operation. They weren't disappointed. WorldView 1, orbiting more than 300 miles above the planet, got a clear shot showing the drilling tower and other structures at the facility.

"This goes to our ability to see anywhere on Earth on a daily basis," Chuck Herring, a director in DigitalGlobe’s analysis center, told me today.

The sun is illuminating the scene from the bottom of the picture, which means Vostok's structures and vehicles cast shadows that stretch up toward the top of the frame. The biggest shadow is cast by the station's main residence and office building, just above center. The drilling tower casts a long, thin shadow with a flag on top, above and to the left of the main building.

The shadows arrayed below and to the right of center are probably the vehicles used for overland transport to the Antarctic coast, said Peter Doran, an expert on polar lakes at the University of Illinois at Chicago. "They have these amazing, large vehicles with tracks," Doran told me. "They remind me of something out of 'Mad Max.'"

The square-sided area near the very center of the picture is apparently a built-up berm, most likely part of a storage facility for supplies or ice cores.

DigitalGlobe

This wider version of the WorldView 1 picture of Vostok Station shows more of the Antarctic wasteland surrounding the facility. Compared with the close-up, this view is rotated roughly 65 degrees clockwise. The skiway on which supply planes land can be seen running diagonally from top center to lower left, while the ice road to Russia's Mirny Station on the coast runs from the settlement toward lower right.

Paul Morin, director of the Polar Geospatial Center at the University of Minnesota, said one of the most remarkable things about the picture is ... how unremarkable it looks. "Stations like this look very much the same," he said. "Vostok is one of the most remote places on Earth. These guys have done an amazing feat, drilling at this location."

Doran said it was reassuring to see that everything looked normal, considering all the worries that researchers had about the Vostok drilling operation. Some observers feared that once the drill reached the lake, there'd be an explosive upwelling of water from the reservoir. To get international approval for the operation, the Russians had to conduct a detailed engineering analysis demonstrating that they were proceeding safely and surely.

"Even with all the numbers, you just had to wonder whether they had it right," Doran said. Based on the DigitalGlobe imagery,"it's clear that nothing really unusual happened," he said.

Morin said the imagery from DigitalGlobe and other providers has made a huge difference for scientists studying Antarctica's forbidding frontier. "Before commercial imagery, we had better pictures of Mars than we had of Antarctica," he observed. Aerial imagery of Vostok Station will be particularly helpful for scientists on the outside. "We have to stay abreast of what all these stations look like, because occasionally we have to go there," Morin said.

DigitalGlobe's Herring said his company is building up "a tremendous amount of imagery" every day — five times as much as any other commercial satellite image provider. "Right now our raw imagery archive grows by two petabytes of data per year," he said. That's 2 quadrillion bytes of data, which is a big or a small number, depending on your perspective. It's more image data than all the pictures that are stored on Facebook, but just a tenth the amount of data processed by Google on a daily basis.

No matter how you see it, keeping track of 2 quadrillion bytes' worth of images is a challenging task, but Herring said DigitalGlobe is up to the challenge.  "Combining our constellation with the analysis center, we've seen a huge value, a tremendous amount of value for our customers," he said.

WorldView 1 and DigitalGlobe's other satellites will continue to keep watch on Vostok, "to monitor change and understand the facility, and validate what's said in the press about what's going on there," Herring said. For now, the Russians have closed up shop at the drilling site and hunkered down for the Antarctic winter. The researchers will return to their field work in a few months.

In the meantime, the Russians will have to lay out their plans to extract water samples from the lake itself. "If they're going to do that, they've got to write a new document that would be approved by an international body," Doran said. "They're not done. This was just the first pinprick."

Where in the Cosmos? Today's satellite picture of Vostok Station served as this week's "Where in the Cosmos" picture puzzle on the Cosmic Log Facebook page. Every week, we're serving up a mystery picture and asking Facebook fans to tell us what the picture shows. It took only four minutes for Martin Lynge of Nuuk, Greenland, to register the right answer — and as a reward, we're sending Martin a pair of 3-D glasses (courtesy of Microsoft Research) plus a 3-D picture of yours truly that will serve to scare the neighbors in Nuuk. To get in on next week's "Where in the Cosmos" contest, be sure to check out the Facebook page and hit the "like" button.

More fun with space pictures:

• Feb. 3: Moon craters and Mars colors
• Jan. 27: 3-D color map of the universe
• Jan. 20: Stephen Hawking's curios explained 

Alan Boyle is msnbc.com's science editor. Connect with the Cosmic Log community by "liking" the log's Facebook page, following @b0yle on Twitter or adding Cosmic Log's Google+ page to your circle. You can also check out "The Case for Pluto," my book about the controversial dwarf planet and the search for other worlds.