Atmospheric gases scatter blue wavelengths of visible light more than other wavelengths, giving the Earth’s visible edge a blue halo. At higher and higher altitudes, the atmosphere becomes so thin that it essentially ceases to exist. Gradually, the atmospheric halo fades into the blackness of space. (Credit:
NASA's Earth Observatory.)
Astronauts aboard the Space Shuttle Discovery recorded this rarely seen phenomenon of the full
Moon partially obscured by the
atmosphere of Earth. The image was recorded with an electronic still camera at 15:15:15 GMT, Dec. 21, 1999. (Credit:
NASA.)
Satellite image of Cyclone Gafilo, a powerful
Category 5tropical cyclone which struck
Madagascar in March 2004, causing devastating damage. This was taken just before landfall, when the system was at its peak intensity about 333 km (207 mi) east of Madagascar, with sustained windspeed of 260 km/h (160 mph). At least 250 people were listed dead, with more missing, and 300,000 people were left homeless due to Gafilo. (Credit:
Terra satellite,
NASA.)
Erg Chebbi (
Arabic: عرج شبّي) is the sole
Saharanerg in
Morocco. It is 22 km long (North-South) and 5 km wide. Its dunes reach a maximum height of 150 meters. It is located roughly 40 kilometers south-east of
Erfoud. The local center for tourists is the village of
Merzouga. (Credit:
Rosa Cabecinhas and Alcino Cunha.)
This map shows the tracks of all
tropical cyclones that formed worldwide from 1985 to 2005. The points show the locations of the storms at six-hourly intervals and use the color scheme shown on the right from the
Saffir-Simpson Hurricane Scale. (Credit:
Nilfanion.)
Winter is one of the four
seasons of temperate zones.
Meteorological winter is the season having the shortest days (which vary greatly according to
latitude) and the lowest temperatures. (Credit:
Richard Fabi.)
Cirrus clouds are composed of
ice crystals and shaped like hairlike filaments. They are formed at an altitudes above 5000 metres (16,500 feet). The streaks are made of
snowflakes that are falling from the cloud and being caught by the high level winds. The streaks point in the direction of the wind and may appear straight giving the clouds the appearance of a comma (
cirrus uncinus), or may by seem tangled, an indication of high level
turbulence. (Credit:
Piccolo Namek.)
Antarctica, the
continent surrounding the
Earth's
South Pole, is the
coldest place on earth and is almost entirely covered by
ice. Antarctica was discovered in late January
1820. Too cold and dry to support virtually any vascular plants, Antarctica's flora presently consists of around 250
lichens, 100
mosses, 25-30
liverworts, and around 700 terrestrial and aquatic
algal species. (Credit:
NASA.)