Top Ten Astronomy Picture

1: That First Small Step

That shiny white thing in the upper left where humans first slipped the surly bonds of Earth, and walked on another world.

2: The Detail’s in the Devil Mars has an atmosphere, though it’s thin: about 1% of Earth’s atmospheric pressure, it doesn’t seem capable of doing much. But when you have a robotic probe like the Mars Reconnaissance Orbiter and its 50-cm resolution orbiting the Red Planet, you see far, far more, and learn that the air of Mars can create beauty.The image above shows a region of Mars near its mid-lower northern latitudes. It’s a close-up of the bed of a crater, and you can see the ripples of sand dunes, endemic on the Martian surface. The sand is similar to beach sand here on Earth, but is dark in color because it’s made of basalt, a greyish rock. Then why is Mars so red? It’s because of much finer-grain dust, which is reddish in hue. The dust lies on top of the sand, making everything look red.

3: Eternally Stargazing The skies there must be incredibly dark; located about 3000 km west of Chile in the Pacific Ocean, you might wonder how much more black the nights could be, and of course the answer is none.

4: Hubble’s Metamorphosis In May 2009, the Space Shuttle Atlantis roared into orbit to rendezvous with the ailing Hubble Space Telescope. After several exciting spacewalks, astronauts succeeded in making many upgrades to the venerable observatory, including installing new high-resolution cameras, fixing old shorted-out cameras, and replacing needed hardware like computer parts and gyroscopes. We all waited anxiously, and finally, in September, new images from the refurbished ’scope were released.

5: Beautiful plumage

The Cassini spacecraft has been orbiting Saturn since 2004, and has been returning a virtual firehose of incredible images and science ever since. I’d argue it’s one of the most dramatically successful space probes of all time. It’s certainly revolutionized our view of the ringed planet over and again.

6: The Cosmic Hand of Destruction This eerie shot, from the Chandra X-ray Observatory, is actually showing extremely hot gas around a pulsar, the rapidly spinning core of a once-exploded star. The pulsar — named PSR B1509-58 — is buried in the bright spot in the "wrist" of this structure. As the pulsar spins, it generates extremely strong magnetic winds which blow out and interact with previously existing gas in the region. Dense knots of gas form, and those are at the tips of the "fingers" (if only they were holding a "laser"). The red gas above is probably expanding material from the supernova explosion that formed the pulsar in the first place, something like 1700 years ago.

7: The Lunar abyss stares back One of the biggest news stories of the year was the confirmation of large quantities of water on the Moon, stored in the endless dark of crater floors at the lunar poles. If the crater is deep enough sunlight can never reach the bottom, and the temperature stays chillingly cold. Water can come in the form of comets, for example, which impact the Moon and blast water molecules over the surface. When sunlight hits them the molecules quickly fall apart, forming hydrogen and hydroxyl ions. But if the water settles to the floor of a polar crater, it can stay intact. Over billions of years, it builds up.

8: Earth from space

In November 2009, Rosetta swung by the Earth for its third and final assist. While it was still over 600,000 km (360,000 miles) away, it took this remarkable image of our home.

9: A Computer’s Spot in the Sun

30 Dark blemishes on the Sun have been known since antiquity; when the setting Sun’s disk is dimmed by dust in the air, you can sometimes see sunspots against its reddened face. Those are monster spots, and very rare, but even the normal run-of-the-mill sunspots aren’t well understood.

10: Pandora’s Galaxy

NGC 4522 is a spiral galaxy that lies 60 million light years away, a denizen of the Virgo Cluster, the nearest such collection of galaxies to our Milky Way.