Week's Best Space Pictures: Cassini's Crescent and Cassiopeia's Soul

Mars carves new channels and amateurs catch a falling star in this week's best space pictures.

NASA released this stunning photo of the Monkey Head Nebula to celebrate Hubble's 24th year in orbit.

Happy birthday, Hubble. Astronomers snapped this image of the Monkey Head Nebula—released on March 17—in honor of the famous space telescope's 24 years in orbit.

The nebula, formally known as NGC 2174, resides 6,400 light-years away, within the Orion constellation. It's a region known as a stellar nursery, where clouds of gas and dust coalesce to form young stars. (Learn more about star formation.)

Saturn looms as a thin crescent in this image, released on March 17, taken by cameras on board the international Cassini spacecraft.

Part of the planet's famed rings paint the left side of the image, breaking up Saturn's profile. Cassini captured the image from 1.4 million miles (2.3 million kilometers) away, in orbit around the ringed planet. (See "Saturn's Largest Moon Would Host Really, Really Weird Life.")

Before (left) and after (right) comparison of the Terra Sirenum region on Mars reveal a new gully (arrow) carved sometime between November 2010 and May 2013. Cameras aboard the Mars Reconnaissance Orbiter took the images.

Although it looks similar to gullies on Earth that are formed by flowing water, this Martian gully is likely the result of carbon dioxide frost, or dry ice. Planetary scientists can't be sure exactly when the new channel formed, but similar occurrences tend to happen during winter on the red planet. (See "Martian 'Blueberries' Really Pieces of Meteorites?")

A meteor streaks through the night sky near Wellington, New Zealand, in an image submitted to Your Shot on March 16.

Mark Gee traveled 20 minutes outside the city to photograph part of the Milky Way galaxy (map), and was lucky enough to catch a falling star.