Star trails create arches over the horizon in a long-exposure picture of the night sky taken from Mount Kilimanjaro in Tanzania.
The shot, captured in July and released this week, shows the apparent motion of the stars around Polaris, the star that's almost exactly aligned with Earth's north celestial pole. Also called the North Star, Polaris is the brightest dot in the constellation Ursa Minor.
Equatorial regions, such as Kilimanjaro, are the only places on Earth where the celestial poles sit right at the horizon.
Seen in a radar image released last week, Nimrod Glacier in Antarctica resembles a fast-flowing river of molten metal. In reality, the 84-mile-long (135-kilometer-long) glacier moves just six and a half feet (two meters) a day, carrying ice across the Transantarctic Mountains, from eastern Antarctica to the Ross Ice Shelf.
Taking images such as this one—from the German Aerospace Centre's TerraSAR-X satellite—year-round can help researchers measure the glacier's flow speed and study its structure.
Image courtesy DLR
It may look like mold under a microscope, but the above image, released December 15, is actually a map of where sunlight hit the moon's south pole.
Over six months, NASA's Lunar Reconnaissance Orbiter took 1,700 pictures of the moon's polar region. Each shot was then converted to a binary image: A pixel was dubbed a one if it was illuminated and a zero if it was dark. Stacking the images generated the illumination map.
Understanding which parts of the moon are always in darkness may be key to planning future missions to the moon—at least one permanently dark crater, for instance, seems to hold a significant cache of water ice. (See "Water on the Moon Confirmed by NASA Crashes.")
Image courtesy NASA/ASU
The tan-colored waters of Lago Alajuela stand in contrast to the dark green of Panama's surrounding rain forest in a December 17 picture taken by NASA's Earth Observing-1 satellite. Alajuela is one of two artificial lakes linked to the Panama Canal (not pictured). This shot was captured days after heavy rains forced officials to close the canal for the third time in its 96-year history.
The torrential downpour not only raised water levels in the lakes, they also choked the waters with sediments, forced thousands of residents to evacuate, washed out roads, and caused deadly landslides, according to NASA.
Image courtesy NASA Earth Observatory
"Colored" by Saturn
To human eyes, the icy surface of Saturn's moon Rhea would appear fairly monotone. But when viewed in a combination of infrared, ultraviolet, and green wavelengths, Rhea comes alive with color, as seen in a composite picture from NASA's Cassini orbiter released December 20.
The shot shows the hemisphere of Rhea that always faces Saturn. The left side of the visible disk faces in the same direction that Rhea orbits around Saturn.
Color differences are most likely due to regional changes in surface composition or the sizes and structures of the grains in the moon's icy soil. Such changes could be driven by debris preferentially hitting certain parts of the moon. The colors could also be caused by an effect called magnetic sweeping, in which charged particles in Saturn's magnetic field sweep over Rhea and become implanted in the soil.
Image courtesy NASA/SSI
The surf's not actually up off the coast of South Island, New Zealand: The large waves that seem to be rolling toward land aren't in the water, but in the air above. This December 21 picture, from NASA's Terra satellite, captured a phenomenon called atmospheric gravity waves.
Such waves form when buoyancy pushes air upward while gravity pulls it downward, giving rise to oscillations in the air. At the low point of a wave, more air touches the surface of the ocean, roughening the otherwise smooth water.
When sunlight hits water at the same angle as a satellite's view, smooth areas reflect light like mirrored surfaces while rough regions scatter light and appear darker. That means if atmospheric gravity waves are present, their pattern becomes visible in the water.
Image courtesy MODIS/NASA
Shuttle in Waiting
The external fuel tank for the space shuttleDiscovery undergoes examination in the Vehicle Assembly Building at NASA's Kennedy Space Center in Florida on December 23.
Problems with the tank scrubbed two launch attempts for Discovery earlier this year. The shuttle's next chance to fly to the International Space Station will be no earlier than February 3, 2011, NASA officials say.
Photograph courtesy Frank Michaux, NASA
Lasers on Mars
Dr. Evil would be glad to know that NASA's Mars Science Laboratory will be going to the red planet with a laser on its head.
The Chemistry and Camera instrument, seen above before a recent test firing at Los Alamos National Lab in New Mexico, uses a pulsed laser beam to vaporize a pinhead-size piece of material. The resulting flash of light can be analyzed to identify chemical elements inside the material.
The new laser technique will allow the rover, due to launch next year, to directly identify some of the lighter elements, such as carbon, oxygen, and hydrogen—something earlier Mars rover missions weren't able to do.
Photograph courtesy LANL/NASA
The moon's highs and lows are revealed in full color in a new topographic map produced by NASA's Lunar Reconnaissance Orbiter and released December 17. Using a laser pulse split into five beams, the spacecraft has made the most accurate map yet of the contours of the entire lunar landscape.
The above picture shows the moon's southern hemisphere, with higher regions seen in red and low places in blue.
The nebula lies about 5,800 light-years from Earth and is home to a cluster of relatively young stars born about eight million years ago. Powerful radiation from the stars is sculpting the surrounding dust, creating the ring-like structure seen at the center of this frame.
In visible wavelengths, much of the dust can't be seen. Instead the nebula glows with light from hydrogen gas being charged by the stars' radiation. The resulting object resembles a sprinting fowl, earning the space cloud its common name: the Running Chicken nebula.