NATIONAL GEOGRAPHIC'S BEST SPACE PICTURES THIS WEEK XXIX

Week's Best Space Pictures: Ripples Run, Astronauts Walk, and a Star Pulses
By Jane J. Lee, National Geographic News, 10 October 2014.

Ripples race across Mars, astronauts go for a walk, and a star pulses in this week's best space pictures.

1. No Ladder Needed

NASA astronaut Reid Wiseman (pictured) went for a walk on October 7 - a space walk.

Even astronauts need air-conditioning. Wiseman and fellow Expedition 41 crew member Alexander Gerst relocated a failed cooling pump to a storage area on the outside of the International Space Station.

The spacewalkers also installed backup power gear for robotics equipment on the orbiting lab. The 6-hour-and-13-minute effort was the first of three planned space walks for this expedition.

2. In a Different Light

Two images of one galaxy - dubbed Messier 82 - shine forth in an October 8 view from the Jet Propulsion Laboratory in Pasadena, California.

The picture on the left was taken with the Hubble Space Telescope, which captures visible light, and the one on the right was taken using the Chandra X-ray Observatory, which detects x-rays.

The double-barrelled look tells astronomers where the stellar action is happening inside Messier 82.

3. Rapidly Racing Ripples

Dunes chase ripples across part of Mars known as Nili Patera. This red planet region changes so often that HiRISE - the orbiter that passes over Nili Patera every couple of months - can't keep track of all the avalanches and dune collapses.

4. Cosmic Lighthouse

A pulsar in action appears in this view from a NASA/JPL animation. Pulsars seemingly "pulse" with light. They're made of a special, spinning type of neutron star, the superdense remnant core of an exploded star. Astronomers compare these pulses to the rotating beams seen from lighthouses.

In the animation, two spots on a pulsar pull in material from a surrounding disk of dust and debris. When the stellar stuff gets sucked into the star, it heats to extreme temperatures and cause two bright spots to appear. As the pulsar spins, observers see those bright spots as bursts of light. (See "Giant Blast of X-Rays Traced to Dead Star.")

Astronomer Jocelyn Bell Burnell discovered pulsars when she was still a graduate student at Cambridge University in 1967. The discovery garnered a Nobel Prize in physics, but the credit went to Burnell's supervisor Anthony Hewish, and a colleague of his, Martin Ryle. (See "6 Women Scientists Who Were Snubbed Due to Sexism.")

5. "Duck and Cover"

The sky isn't falling on Mars, but spacecraft orbiting the planet aren't taking any chances. An illustration demonstrates the "duck and cover" manoeuvre NASA will execute to protect its Mars orbiters (orange line) from an October 19 visit by comet Siding Spring (track in blue).

The comet will come within roughly 87,000 miles (139,500 kilometres) of the red planet's surface, screaming along at about 126,000 miles (202,777 kilometres) per hour.

Siding Spring's debris field will wash past Mars, and although scientists want to collect as much data as they can, they plan to use the planet as a shield to protect important instruments. They also hope the space agency's two working Mars rovers, Curiosity and Opportunity, catch the first ever view of a comet seen from the surface of another world.(See "NASA Preps Mars Orbiters for Comet Close Encounter.")

6. A Dusty Panorama

An enormous dust storm obscures the azure waters of the Persian Gulf in an image released on October 6. Astronauts on board the International Space Station captured the panorama sweeping over Iraq and its adjoining body of water while orbiting roughly 250 miles (402 kilometres) above the Earth.

Photo gallery by Mallory Benedict and Sherry L. Brukbacher.

[Source: National Geographic News. Edited. Some links added.]