Friday, May 1, 2009

THE BEST PICTURES OF EARTH: Reader Picks of NASA Shots

Twin Blue Marbles (October 9, 2007) As beautifully simple as they may appear, the above images of Earth took an armada of NASA instruments and artists to compile.

Factoring in readings of polar sea ice, city lights, radar-based topography, and the light reflected off the planet's myriad surfaces, the above "Blue Marble" images show Earth from both sides in all its colorful glory.

STEREO's First View of the Sun (January 3, 2007)

Loops of highly charged particles shoot out from the sun's roiling surface, as seen in ultraviolet by the twin STEREO spacecraft.

The sun's surface regularly pumps out these coronal mass ejections--explosions caused by magnetic stress in the sun's atmosphere, which is shown above at roughly a million Kelvin (1.8 million degrees Fahrenheit). Solar flares surge into space with each eruption, causing auroras on Earth and disrupting communications and radio systems.

The active region at the base of each blast can be seen from Earth as sunspots, but the ultraviolet loops can only be observed from space.

Earth's City Lights (October 23, 2000)
Twinkle, twinkle, little cities. A spacecraft originally designed to look at clouds by moonlight was employed to make this view of Earth's artificial lighting.

Showing urbanization rather than population, this light data has been used by NASA scientists to analyze urban sprawl and the technological advancement of the world's cities.

The United States interstate highway system can be seen as a fine lattice, while the Nile River is a bright thread, thanks to the cities on its shores.

The image also reveals Western Europe "out-glowing" China, the Trans-Siberian Railroad stretching across Asia, and the bright arc of Japan hovering above a mostly dark Australia.

Agricultural Patterns (May 30, 2006)

Like patchwork quilts, satellite views of farming patterns around the world form the above montage of images taken by the Terra satellite.

At top-left, a regular grid pattern suggests that agriculture was shaped by 19th-century surveying in Minnesota. Meanwhile, center-pivot irrigation in Kansas is responsible for the circles visible in the second image. A well in the middle of each field serves as a pivot point for wheeled, spraying watering machines.

In the top-right image of northwest Germany, small and disorganized fields can be traced back to the less-planned farming of the Middle Ages.

Curious pie-shaped fields in the lower-left image are the result of a planned settlement near Santa Cruz, Bolivia. At the center of each field is a village, while a buffer of rain forest separates each community.

In Thailand, at bottom-center, rice paddies just outside Bangkok form skinny slices. The purple fields are flooded, a normal part of rice's life cycle.

At bottom-right, Brazil's woodland-savanna cerrado contains massive farms, a by-product of the flat land's inexpensive price.
Sunspots at Solar Maximum and Minimum (March 20, 2009)

It's been quiet lately on the sun, as seen in the two right-hand images. The normally stormy star is in a period of solar minimum, with fewer sunspots in 2008 than have been observed since 1957. But nine years ago the sun was vomiting intense magnetic activity and solar flares, as seen in the left-hand solar maximum images.

The top row of images depicts the sun as observed in visible light by the SOHO spacecraft, while the bottom row uses the same craft's Extreme Ultraviolet Imaging Telescope to capture solar flares.

Severe space weather, such as that shown in the left-hand images, poses a threat to humans' high-tech infrastructure, damaging electronic and electrical equipment.

Earth, as Seen From Saturn (January 16, 2007)
April 28, 2009--They're the best of Earth, as judged by Earthlings. NASA's Earth Observatory today announced the ten most popular pictures of our home planet from its Image of the Day catalog, the culmination of a user-voted contest marking the tenth anniversary of the observatory's Web site.

Providing many a computer wallpaper for space-savvy Internet users, the daily-updated site showcases images from NASA missions that collect information about Earth.

The most popular image was captured by instruments aboard the Cassini spacecraft and digitally composited by NASA illustrators to show Saturn and its rings--and a tiny, dot-size Earth, seen from almost a billion miles (more than a billion kilometers) away.

At the precise moment shown, Saturn was positioned between Cassini and the sun, so that the probe's cameras didn't have to contend with the star's intense glare. In addition to revealing Earth in the distance, being in Saturn's shadow helped the satellite spy previously unseen faint rings around the gas giant.

Ocean Sand, Bahamas (September 13, 2002)

Though viewers would be forgiven for thinking the above picture a work of abstract art, the image is actually a photograph captured by the Earth-orbiting Landsat 7 satellite.

Ocean currents in the Bahamas made the sand-and-seaweed sculpture in much the same way that winds create sand dunes in the Sahara.

Atafu Atoll, Tokelau, Southern Pacific Ocean (April 6, 2009)
A tiny atoll, part of a New Zealand territory, is seen as photographed from the International Space Station by an astronaut.

The Atafu Atoll is one of four atolls and islands that are part of the Tokelau Islands. Geology suggests that a volcanic island created the atoll. Coral reefs likely formed around the volcano, which then eroded beneath the water, leaving a ring of sand and reefs.

Atafu's main village can be seen to the left as a collection of small grey dots. Around 500 people responded to a 2006 census of the atoll

The Southern Lights (January 25, 2006)


The aurora australis, or southern lights, glimmer green over Antarctica in the picture above.

Four days after a massive solar flare, NASA researchers obtained readings from the now-defunct IMAGE satellite, which monitored Earth's magnetic field.

Overlaying the data onto a "Blue Marble" satellite photograph of Earth resulted in both the image above and an animation of the solar storm's effects on Earth's atmosphere.

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