Space Pictures This Week: Martian Gas, Cloud Trails

Martian Ice Fans

Image courtesy U. Arizona/NASA

In a picture released January 24 by NASA and the Jet Propulsion Laboratory, black streaks of sand fan out over a seasonal ice cap at the Martian north pole.

Unlike on Earth, ice caps on the red planet are made of frozen carbon dioxide—similar to the dry ice found in Halloween punch bowls.

When sunlight filters down through the Martian ice, it warms the sand—and the ice in contact with the dirt—turning solid ice directly into a gas in a process called sublimation. Once the trapped gas finds an outlet it erupts, dragging sand from Mars' surface along with it. (Related: "Mars Snow Falls Like Dry Ice Fog.")

Published January 28, 2013

Night-Shining Clouds

Photograph courtesy NASA

These luminous blue clouds at the edge of space are called polar mesospheric clouds, or noctilucent clouds. Formed between 47 to 53 miles (76 to 85 kilometers) up in the atmosphere, they're most visible during late spring and early summer in both the Northern and Southern Hemispheres.

They get their blue glow when the sun dips below the horizon, shrouding the ground in darkness but giving off enough illumination to light up the clouds. The yellow-orange band at the bottom of the blue layer is the stratosphere.

This picture, released January 21, was taken by the crew of the International Space Station as they passed over the Pacific Ocean south of French Polynesia (map).

Published January 28, 2013

Mercury’s Michelangelo

Image courtesy JHUAPL/CIW/NASA

The Michelangelo basin, shown here in a close-up released January 24, resides in the Michelangelo quadrangle located in the southern polar regions of Mercury.

The image was taken as part of NASA's MESSENGER mission, whose satellite is the first spacecraft to orbit this innermost planet.

Since Mercury has no atmosphere, there is no wind to erode the many impact craters stamped onto its surface.

Published January 28, 2013

Snail Trails?

Image courtesy GOES Project/NASA/NOAA

NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) onboard the Aqua satellite snapped this image of clouds across the eastern Pacific, off the west coast of the U.S. and Canada, on January 15.

Scrawled across the fluffy clouds like drunken snail trails are ship tracks (center). These human-made clouds form when atmospheric water vapor condenses on small particles lofted into the air from a ship's exhaust. (See pictures of a possible new cloud type.)

Published January 28, 2013

See More of Our Favorite Space Pictures

Photograph courtesy NASA

Published January 28, 2013