NATIONAL GEOGRAPHIC'S SPACE PICTURES THIS WEEK LXIII

Space Pictures This Week: Mercury's Marks, Miracle Delta
By Andrew Fazekas, National Geographic News, 21 June 2013.

A celestial penguin guards her egg and wildfires are spotted from space in this week's best space pictures.

1. Wind Shadow

Milky-coloured ripples on the Atlantic Ocean trail behind the Canary Islands (map) off the west coast of Africa in this June 15 image snapped by NASA's Terra satellite.

Thanks to a vantage point 450 miles (725 kilometres) above the Earth, strange patterns caused by strong winds on the ocean's surface become visible in the play of sunlight on the water.

The rocky, volcanic islands redirect the strong northwest winds that come up against the coast, forming a wind shadow on the southwest side of the islands. This shadow creates distinct helical cloud trails and alternately smooth and choppy waters, which change how light is reflected.

2. Night Light

Photograph by Dennis Mammana, TWAN

Like a celestial pipe organ in a grand cathedral, the skies above Fairbanks, Alaska, come alive with a curtain of green auroras in this image snapped in March. (Learn how a stunning aurora video was made.)

"'Normal' photos tend to blur [auroras] and don't capture the true detail of these marvellous curtains, so to freeze the action as much as possible, I kept my exposure time to only a second," said photographer Dennis Mammana on The World At Night website.

3. Galactic Penguin

The Hubble Space Telescope snapped this uncanny image, released June 20, of two interacting galaxies that look like a penguin guarding her egg.

Known collectively as Arp 142, the galactic pair lie some 326 million light-years from Earth in the constellation Hydra.

Over a period of millions of years, the celestial bird-shaped galaxy has lost its distinct pinwheel structure. Its red, spiral arms have become distorted by the pull of gravity from the neighbouring elliptical, egg-shaped galaxy.

Above the pair is a lone, unrelated bluish galaxy located about 230 million light-years from Earth.

4. Miracle Delta

This radar satellite image, released June 7, shows where southwestern Africa's Okavango River (bright yellow) empties into the Okavango Delta in northern Botswana. (Read about "Africa's Miracle Delta" in National Geographic magazine.)

This portrait of one of the most popular safari destinations on the continent is a composite based on images taken by the European ENVISAT orbiter between September 2009 and October 2010.

The Moremi Game Reserve appears in purple at the centre of the image, while in the lower right corner a cluster of reflections marks the town of Maun.

5. Mercury's Marks

This high-resolution image of the craggy surface of Mercury, released June 20, was taken by the cameras aboard NASA's MESSENGER orbiter. Multiple impact craters with fresh ray patterns appear scattered across an ancient lava basin.

Slightly larger than Earth's moon, Mercury lacks a meaningful atmosphere, so there is nothing to stop impacts from occurring and covering its sun-scorched surface with craters.

6. Where There's Smoke

The root cause of the record-setting pollution levels that have besieged Singapore this past week is clearly seen in this orbital photo from NASA's Aqua satellite taken on June 19.

Thick clouds of smoke originating from illegal wildfires on Sumatra (below, left) appear to blow straight toward southern Malaysia, where a choking haze of pollutants has blanketed Singapore. (Related: "Pollution in Singapore Hits Record Level.")

[Source: National Geographic News. Edited.]