Summer and winter leave their marks on Mars, too, as seen in a crater slope that is lined with markings that advance and retreat with the seasons. (See also: "Mission To Mars".)
Called "recurrent slope linea," the markings on the slope of the crater near Valles Marineris on Mars grow longer in warm months, and then retreat as the weather cools over the course of the Martian year. Scientists suspect that briny water or liquid carbon dioxide under the surface warms and colors the lines during warmer months on Mars.
Photograph courtesy NASA/JPL-Caltech/Univ. of Arizona
Can you see the crab? The famed Crab Nebula, first observed by Chinese astronomers in 1054, is the remnant of a stellar explosion, or supernova.
Astronomers this week reported the discovery of chemical traces of the gas argon amid the blasted-apart star debris of the nebula, the first detection of a noble gas in space.
That's not a surprise, since astronomers have known since the 1930s that most of the lighter elements in the cosmos are released from exploding stars, but the discovery makes a nice confirmation. The density of the gas seen in the nebula can also help explain the supernova's original star.
Photograph courtesy ESA/Herschel/PACS/MESS Key Programme Supernova Remnant Team; NASA, ESA and Allison Loll/Jeff Hester (Arizona State University)
The largest sea on Titan, Kraken Mare, appears as the body in black and blue resting just below the moon's north pole, in the center of the map. Most of the lakes appear to be liquid ethane and methane, basking in Titan's surface temperature of -290° Fahrenheit (-179° Celsius).
The second largest moon in the solar system, Titan is the only one with a thick atmosphere. Planetary scientists are still unraveling how Titan's weather works, looking for an explanation of why the lakes cluster on the northern half of the moon.
PHOTOGRAPH COURTESY NASA/JPL-Caltech/ASI/USGS
Asteroids Streak Past Dying Star
Asteroids dash past a dying star, the Helix nebula, seen in this image from NASA's Wide-field Infrared Survey Explorer (WISE) spacecraft.
Far from our solar system, a remnant white dwarf star at the heart of the nebula heats gas and dust sloughed away from the original star at the center of the nebula. The heated gas and dust glows, creating the nebula's beautiful appearance.
Much closer, asteroids (and the occasional spacecraft) zip past the nebula, seen as streaks across the sky. NASA has repurposed the WISE spacecraft as an asteroid hunter, taking advantage of its wide-field imaging capabilities.
PHOTOGRAPH BY NASA/JPL-CALTECH/UCLA
Saturn's Beguiling North Pole
Effectively a hurricane capping Saturn, the six-sided jet stream bounding the north pole of the planet is revealed by a Cassini spacecraft overflight.
Taken over ten hours on December 10, the images show "the hexagon" rotating about the top of the ringed planet. Inside the hexagon, vortices swirl in the opposite direction. The largest, the white swirl on the bottom right, is some 2,200 miles (3,500 kilometers) wide.
PHOTOGRAPH COURTESY NASA/JPS-CALTECH/SSI/HAMPTON UNIVERSITY