Wilkins Ice Bridge: This picture shows the Wilkins Ice Shelf, on the western side of the Antarctic Peninsula. An ice shelf is a thick slab of ice that is attached to a coastline. We see here varying sizes of ice fragments mixed with ice mélange. A crack in the east reveals dark ocean water below.

Image Credit: NASA

Family Photo: Mars rovers appear to be shrinking with age! The biggest, baddest, newest rover is the Mars Science Laboratory rover (right). It's the size of a small sport-utility vehicle. Next up in size are the Mars Exploration Rovers (MER) Spirit and Opportunity (left, only one pictured here). Each is the size of a dune buggy. And in left center is the first-generation rover, Sojourner, which is the size of a microwave oven.

Why are the rovers getting bigger? The answer is one word: science. The mass and volume of science instruments -- tools the rovers use to study the Martian surface and environment -- have remained fairly constant at about 10 percent. To determine if Mars ever could have supported life, the Mars Science Laboratory rover will travel farther, carry more instruments, and sample more rocks and soils than ever before. Like a car with more gizmos, the newest robotic beast has to evolve to carry all that gear!

Image Credit: NASA/JPL-Caltech