NATIONAL GEOGRAPHIC'S SPACE PICTURES THIS WEEK LXII

Space Pictures This Week: Surfing Mars, Mercury Rising
By Andrew Fazekas, National Geographic News, 14 June 2013.

Mars reveals its secrets, a powerful Midwestern storm is viewed from orbit, and a new type of star is discovered in this week's best space pictures.

1. Room With a View

On June 3, 2013, NASA astronaut Chris Cassidy took advantage of the ultimate panoramic views of the cosmos, by stationing himself with his camera and telephoto lens inside the International Space Station's observation deck, known as the Cupola.

With its seven large portholes, the 10-foot dome-shaped module offers the perfect place to snap spectacular photos of celestial objects and Earth, some 250 miles (400 kilometres) below.

The Cupola is also used by the ISS crew as a cosmic control tower from which spacewalking activities and spacecraft-docking operations can be monitored. Like a crane operator inside a control cabin, astronauts use robotic workstations to command the station's robotic arm to help with assembly and maintenance of the station.

2. Surfing Martian Dunes

Bizarre images like the one above from NASA's Mars Reconnaissance Orbiter reveal multiple parallel grooves along the slopes of giant Martian sand dunes that have baffled planetary scientists for nearly a decade.

New research, however, now shows that these deep furrows, stretching out to 1.6 miles (2.5 kilometres) are formed only during early spring on dunes that are covered in layers of carbon-dioxide frost (also known as dry ice) during winters.

As the season changes and temperatures rise, the ice begins to crack and melt. Like miniature hovercrafts, ice blocks break off near the tops of the dunes and surf down on a cushion of vapours as the ice sublimates, creating the linear gullies behind them.

3. Stellar Gems

Shining like a collection of cosmic jewels 7,000 light-years from Earth, the open star cluster pictured above has revealed a previously unknown type of variable star.

Using a large telescope in the high Atacama Desert in Chile, a group of Swiss astronomers spent seven years studying and measuring the brightness of NGC 3766, a loosely packed group of 3,000 stars in the southern constellation Centaurus. Researchers discovered that 36 member stars within the constellation had highly unusual and never-before-seen patterns in the fluctuation of their brightness.

The cause of these changes in light output is yet to be determined, but astronomers are saying that the very existence of this new class of suns is a challenge to our understanding of stellar life cycles.

4. Boiling Storms

This highly detailed infrared image showing a powerful storm sweeping across some Midwestern states on June 12, 2013, is courtesy of the Earth-observation Suomi NPP satellite. Strong storms - resembling spreading molten lava - are visible near the bottom of the image, with parts reaching as far as Pennsylvania and Maryland. In these storms, warm, moist air rises, leading to instability in the atmosphere and generating strong winds, hail, and even tornadoes.

Launched in 2011 the Suomi National Polar-orbiting Partnership (NPP) mission is a partnership between NASA, the National Oceanic and Atmospheric Administration, and the Department of Defense and is designed to collect data on both short-term weather and long-term climate change.

5. Watery Mars Secrets

As it approaches its tenth anniversary in space, the Mars Opportunity rover spent much of May 2013 making a close inspection of a distinctly pale rock, seen at the centre of this image, while perched on top of Matijevic Hill, at the rim of the Endeavour crater.

Using its on-board rock-abrasion tool and x-ray spectrometer, the rover detected the distinct chemical fingerprints of clay minerals in the rock target, which indicates to scientists that it must have been altered at one point by water.

6. Mercurial Horizon

This might appear to be Earth's moon, but in fact this image is a striking portrait of Mercury's crater-filled surface taken by NASA's MESSENGER orbiter on April 23, 2013.

Mercury's southern hemisphere has many impact craters with central peaks, including the distinct bright spokes radiating out of the 50-kilometre-wide (31-mile-wide) Han Kan crater visible near the centre of this image.

Planetary scientists believe that this crater may be relatively young, compared with its surroundings, as evidenced by the fresh, white system of rays. The pattern is believed to have been formed when white-coloured ejecta material from underground was flung into space by an impact, and then splattered back down onto the darker surface.

[Source: National Geographic News. Edited.]