NATIONAL GEOGRAPHIC'S SPACE PICTURES THIS WEEK XCI

Best Space Pictures: Black Holes, Volcanic Smog
By Dan Vergano, National Geographic News, 24 January 2014.

Ole'! Chile showcases its skies and mountain heights in the week's best space pictures, along with Martian mysteries and an intriguing twin quasar.

1. Gleaming Glaciers

Glaciers in the southern Andes as seen from space.

High above Chile, the International Space Station's crew offers up a lovely look at the glaciers gleaming in the southern Andes, as seen in this January 22 image released by NASA. (See also: "Up on the Farm? Five Reasons NASA Needs Space Greenhouses.")

Beloved by hikers, Patagonia was easy to reach for the orbiting space lab, flying some 230 miles (370 kilometres) overhead.

The view shows O'Higgins Lake in Patagonia, one of the deepest lakes in the Western Hemisphere, fed by glaciers that have thinned in recent decades.

2. Sparkling Nebula

How about a swim? The sparkling lights of the Lagoon Nebula would surely entice any space traveller in the mood for a dip, its veil shimmering in this view released on January 22. (See also: "6 Space Events This Week: Taurids, Lagoon, and Neptune.")

Captured by the European Southern Observatory's telescopes in Chile, the nebula hangs only 5,000 light-years away, in the constellation of Sagittarius, the Archer. The giant gas cloud, about a hundred light-years across, is a nursery for new-born stars.

3. Polar Dunes

Sand dunes and the North Pole don't usually come to mind together, but they might for Martians.

The northern polar regions of the red planet, featured in this NASA view released on January 22, boast a dune made of sand mixed with carbon dioxide ice. Jets of carbon dioxide gas venting from the dune have marked its surface with dark spots.

4. Massive Black Holes

A pair of black holes, marked in magenta, whirl their way around a nearby galaxy in this look across the cosmos released on January 21 by NASA's Nuclear Spectroscopic Telescope Array.

At the centre of the galaxy lies a "supermassive" black hole that's millions of times more massive than the sun. Most galaxies have such monsters at their hearts, including our own Milky Way.

But not many boast a nicer "ultraluminous x-ray" black hole, like the second one (on the right) in the image. About a hundred times heavier than the sun, these black holes shine particularly bright with x-rays, for reasons still under investigation by astronomers.

5. Snake Shapes Slither Across Mars

Scared of snakes? Don't look at the wiggly shapes adorning Oxus Patera, a frozen volcanic caldera on Mars, as seen in this NASA image released on January 22.

The scalloped nicks along the spines of the caldera's ridges were likely cracks caused by the expansion and contraction of ice sometime in the ancient past on Mars, scientists suggest.

6. Volcanic "Vog"

Mix volcanic ash with fog and you get "vog," here seen as a blue-grey plume stretching across the South Pacific, pictured on January 7 via NASA's Aqua satellite.

Mixed with the sun's glint off the ocean, the vog stems from the Vanuatu Archipelago northeast of Australia, where two islands, Gaua and Ambrym, frequently release volcanic ash and gases.

7. Mars Gullies

Yowch! Gullies rake across the raw landscape of Mars in an image released this week by the Mars Reconnaissance Orbiter's HiRISE camera.

Some four billion years ago, a comet or asteroid splashed onto the southern highlands of Mars, creating the Argyre Impact Basin just south of the gullies.

After the impact, water or lava flow into the basin may have carved these gullies, which are more than 3.6 miles (6 kilometres) long.

8. Sands of Mars

Where's the water? Planetary geologists ponder what floods carried the bright deposits along the walls of a Martian canyon shown in this image released this week from the orbiting HiRISE camera.

Called Coprates Chasma, the canyon is just one arm of the massive Valles Marineris, a massive trough that stretches for 2,500 miles (4,000 kilometres) across the red planet. While the larger canyon is essentially a massive crack in the crust of Mars, portions of its branch canyons are thought to have been partly carved by water long ago.

9. Cosmic Doppelgangers

Blame Einstein for the optical illusion exemplified by the Twin Quasar, as seen in this Hubble Space Telescope picture released on January 20.

First spotted in 1979 and thought to be two objects, the two bright points at the centre of the image are actually just one quasar, a fantastically powerful, active galaxy very far away. A huge galaxy called YGKOW G1, about four billion light-years away, lies between Earth and this quasar. The giant galaxy actually splits light from the distant quasar into two parts, creating the double image we see as the Twin Quasar.

This "gravitational lens" was first predicted by Einstein in 1936, based on a possibility raised by his theory of gravity. Today astronomers use these lenses to see stars and galaxies, such as the Twin Quasar, that are too distant for normal viewing.

[Source: National Geographic News. Edited.]