On August 14, 1959, a U.S. satellite snapped the first pictures of Earth. Since then, many far more sophisticated imaging satellites have gone up, providing scientists with a wealth of information.
When Winds and Islands Collide
This image shows Von Karman vortices, a row of eddies that alternate in their direction of rotation. These patterns are formed when winds or ocean currents are disrupted, typically by an island or group of islands.
These vortices were formed when the winds moving east across the northern Pacific encountered the Aleutian Islands. The image was taken in 2002 by the Landsat 7 satellite.
The Mississippi River Delta is formed by the accumulation of sediment at the river's mouth. The turbid, nutrient-rich waters enter the Gulf of Mexico, where, every summer, one of the world's largest "dead zones" appears off the coasts of Louisiana and Texas.
This expanse of low-oxygen, or hypoxic, waters is produced by an overgrowth of algae caused by high nutrient concentrations. When the algae die and sink, bacteria consume them and consume the available oxygen, rendering the area uninhabitable.
Last year, the Gulf of Mexico dead zone was estimated at a record 8,800 square miles--about the size of New Jersey. The Advanced Spaceborn Thermal Emission and Reflection Radiometer (ASTER) instrument on the Terra satellite captured this image.
Thanks to improved satellite sensors, scientists have begun to track pollution produced by East Asian forest fires, industrial waste, and urban exhaust. A study released last year estimated that an amount of pollution equivalent to 15 percent of emissions from the U.S. and Canada had traveled to North America from East Asia between 2002 and 2005.
This image shows the pollution over Indonesia and the Indian Ocean in 1997. The white pixels represent the aerosols (smoke) leftover from the fires, while the green, yellow, and red pixels represent rising amounts of tropospheric ozone (smog).
Despite China's heroic efforts to clean up the air for last year's summer Olympics, Beijing remains buried under layers of pollution, the result of rapid industrialization.
The Beijing Traffic Management Bureau recently announced a 12-month extension of its successful traffic restriction program--which was implemented ahead of the games--along with tougher measures to curb emissions. A fifth of the city's 3.6 million private vehicles and a third of government vehicles will stay off the streets.
The city is barely perceptible in this SeaWiFS image, taken on November 20, 1999.
The tracks visible in these clouds off the coasts of France and Spain form when small, airborne sulfate particles emitted by ships and airplanes act as cloud condensation nuclei, or "seeds." The accumulation of these seeds forms the thin streaks of clouds seen here.
Clouds formed by these particles tend to be more reflective and carry more water than usual, but they don't release much precipitation. In the aggregate, these clouds could have a big impact on the global climate.
This image was taken on January 27, 2003, by the MODIS instrument on NASA's Aqua satellite.
This large solar flare, produced by an active region of the sun (AR9077), triggered magnetic storms and knocked out satellites when it created a solar storm on July 14, 2000. Nicknamed the Bastille Day Event, it was the third largest storm of its kind in the past 30 years, and the biggest solar radiation event since 1989. The Slinky-like loops represent magnetic field lines.
The orbiting Transition Region and Coronal Explorer (TRACE) satellite captured this close-up image after the flare erupted. Recorded in extreme ultraviolet light, it covers a 230,000-by-77,000 kilometer area on the sun's surface and shows a one-million-degree solar plasma cooling down.
A "glory" is a ring-shaped, rainbow-like phenomenon that is produced when cloud droplets diffract sunlight like a prism, splitting it into its constituent colors.
The Moderate Resolution Imaging Spectroradiometer (MODIS) on NASA's Aqua satellite captured this image in 2008 over the Pacific Ocean. The features at the upper right are Von Karman Vortices.
Alaska's Mount Redoubt Volcano erupted on March 22, 2009, spewing ash into the atmosphere and obscuring the skies. Four more eruptions followed. According to scientists at the Alaska Volcano Observatory, the ash plume reached a height of 50,000 feet above sea level.
Because they happened at night, the eruptions could only be detected in thermal infrared imagery; high temperatures appear black, while lower temperatures are white. The ash plumes become very cold as they rise high in the atmosphere, making them appear white in the image. The MODIS instrument on NASA's Aqua satellite captured the image on March 23, just as the fifth eruption was about to start.
Australia is often considered the poster child for climate change because of its record heat waves, prolonged droughts, monsoon flooding, wildlife extinction, and mosquito-born illnesses. Southwest Australia in particular has been plagued by severe droughts over the past few years. Following a devastating drought in 2002, which decimated the country's wheat and barley harvests, farmers expanded their crop area, producing record crops in 2003 and 2004.
The green area on the image, which was captured by the MODIS instrument on NASA's Terra satellite on March 16, 2004, represents the expanded crop area.
Phytoplankton blooms form in the Bering Strait when the ice begins to melt. The algae consume nutrients released by the melting ice and use sunlight for photosynthesis. The large blooms provide ample food for zooplankton, which are also plentiful in the Strait.
This Sea-viewing Wide Field-of-view Sensor (SeaWiFS) image, which was captured on June 27, 2000, shows two large blooms. The blue-green water on the right, off the west coast of Alaska, represents a bloom of coccolithophores, a single-celled species known for its white calcium carbonate plates, called coccoliths.
