The French-Italian Concordia station's programme of research includes glaciology, human biology and the atmosphere. ESA uses the base to prepare for future long-duration missions beyond Earth. During the winter, Concordia is under almost total darkness, with an average temperature of -51*C and a record low of -85*C. It is an ideal place to study the effects on small, multicultural teams isolated for long periods in an extreme, hostile environment. Auroras occur frequently over both the North and South polar regions, but are often difficult to see from populated areas Credits: ESA/IPEV/PNRA - E. Macdonald-Nethercott

While observing the turbulent outer atmosphere of the Sun, or corona, Solar Terrestrial Relations Observatory B (STEREO-B) gathered a novel view of our home planet and a celestial visitor in the inner solar system. Comet PanSTARRS was visible to the naked eye from Earth's northern hemisphere at the time, though STEREO might have had the better view.

Alaskan mountains seen from high altitude aboard the NASA P-3B during the IceBridge transit flight from Thule to Fairbanks on March 21, 2013.

NASA's Operation IceBridge is an airborne science mission to study Earth's polar ice. For more information about IceBridge, visit: www.nasa.gov/icebridge. Image Credit: NASA/Goddard/Christy Hansen. Larger image.

One of the Expedition 35 crew members on the International Space Station used a still camera with a 400 millimeter lens to record this nocturnal image of the Phoenix, Arizona area.

Spiral galaxies are some of the most beautiful and photogenic residents of the universe. Our own Milky Way is a spiral. Our solar system and Earth reside somewhere near one of its filamentous arms. And nearly 70 percent of the galaxies closest to the Milky Way are spirals.

But despite their common shape, how galaxies like ours get and maintain their characteristic arms has proved to be an enduring puzzle in astrophysics. How do the arms of spiral galaxies arise? Do they change or come and go over time?

Watching starbirth isn't easy: tens of millions of years are needed to form a star like our Sun. Much like archeologists who reconstruct ancient cities from shards of debris strewn over time, astronomers must reconstruct the birth process of stars indirectly, by observing stars in different stages of the process and inferring the changes that take place.