NATIONAL GEOGRAPHIC'S BEST SPACE PICTURES THIS WEEK L

Week's Best Space Pictures: A Galaxy Glows, Mars Gets a Bull's-Eye, and a Glacier Races
By Jane J. Lee, National Geographic News, 6 March 2015.

Galaxy clusters engage in shenanigans, NASA's next Mars mission paints a target, and a mitten appears on an ice cap in this week's best space pictures.

1. A Dusty Image

Dust wafts across the North African coast in this image taken by NASA's Terra satellite. The plumes originated from Senegal, Mauritania, and Gambia, and their thick brown appearance reveals that the dust was kicked up recently - it is still tightly packed before fanning out over its a long journey across the Atlantic Ocean. The Cape Verde Islands (at left) nestle in the waters just offshore. (For a different kind of long-distance dust journey, read about how cosmic dust can affect you.)

2. Rock Stop

The flat rock in the centre is Opportunity's next Martian target for examination. The image, taken with the rover's hazard-avoidance camera, includes the shadow of Opportunity's "tool turret" (at left).

This long-running rover is way past its expiration date. It arrived at the red planet in January 2004 and was intended for only 90 days of service. (Read about what it's been up to during a decade of exploration.)

3. Running Hot and Cold

Galaxy cluster Abell 2597 runs hot and cold in a feedback loop called cosmic precipitation. Galaxies within this cluster contain hot gases that cool by radiating heat into space.

Those cooler gas clouds then fall toward the supermassive black hole sitting in the centre, where jets shooting out of the black hole heat the gas back up. This seesaw in temperatures regulates the growth of certain galaxies. (See "Winds Blasting From Black Holes Shut Down Star Growth.")

4. Target Acquired

The ellipse painted on this image of Elysium Planitia - a flat plain on Mars - is the landing target for NASA's next mission to the red planet. Slated for launch in March 2016, that mission will delve into the Martian interior to learn how rocky planets formed in our solar system. (Read about Mars's "long-lost" ocean.)

5. A Magnifying Cluster

Galaxy cluster Abell 1689 shines forth in an image taken with the Hubble Space Telescope. These kinds of clusters - bursting with galaxies big and small - contain so much mass that they're able to bend light. (See how new observations of this cluster turned up a dusty oddball.)

If that light comes from more distant objects, the cluster can magnify their apparent brightness, making them visible to observers on Earth. (Learn how a massive galaxy cluster creates a cosmic mirage.)

6. Anyone Lose a Mitten?

No, this isn't a satellite image of the U.S. East Coast - it's a picture of Greenland's Flade Isblink ice cap. The "mitten" (at upper right) is actually a collapsed portion of the glacier courtesy of a subsurface lake that drained into a nearby fjord. (Read about a "lake" the size of West Virginia buried under Greenland's ice.)

The lake drained quickly at about 7,600 cubic feet (215 cubic meters) per second, causing a 230-foot-deep (70-meter) basin to appear. It's just luck that it's in the shape of a mitten. (More: Why is one of Greenland's glaciers racing to the ocean?)

Photo gallery by Sherry L. Brukbacher.

[Source: National Geographic News. Edited. Some links added.]