Earth From Space: 15 Amazing Things In 15 Years

The sensors on Earth-observing satellites can, not only detect the heat given off by wildfires, they can 'count' the number of active fires around the world at any time. They also have provided a decade and a half of imagery of active fires and measurements of their smoke plumes. These views of wildfire from space have now become commonplace, but the sensors have provided scientists with real data on how far smoke travels from its source and how high into the atmosphere. The MISR instrument, the Multi-angle Imaging Spectroradiometer, on Terra has been instrumental in learning more about how wildfire smoke plumes get 'injected' high into the atmosphere and how the plumes mix with clouds.

From orbit, Earth's limb is the fuzzy blue halo that appears above the surface. Instruments like the Microwave Limb Sounder on the Aura satellite observe the limb to get a side view of the atmosphere. This perspective allows scientists to measure atmospheric chemistry layer-by-layer – letting us monitoring the gases that contribute to the ozone hole and for evaluating the impact of clouds on climate change. The Microwave Limb Sounder was the first to measure, from space, all the gases that are part of the ozone depletion cycle, giving scientists the first observations that revealed the full chemical process of ozone depletion as it occurs.

The two variables that still create the most uncertainty about how future climate change will unfold are clouds and tiny airborne particles called aerosols. Some clouds reflect the sun's rays while others trap outgoing heat that would otherwise be emitted to space. Likewise, some aerosols scatter light and cause a cooling effect while others absorb light and cause a heating effect. Aerosols can also seed clouds, further complicating the picture. Scientists have used the MODIS instruments on Terra and Aqua to begin a continuous, long-term record of clouds and aerosols that will ultimately help the science community better understand their mysterious ways. In more recent years, other NASA satellites have been launched to fly in tight formations with Terra and Aqua – providing complementary views of clouds and aerosols from different types of instruments.

Explorers have long gone forth and mapped the terrain of unknown territory, producing detailed topographic maps of mountains, rivers, hills, and plains. The Global Digital Elevation Models produced by the Advanced Spaceborne Thermal Emission and Reflection Radiometer, or ASTER, instrument aboard Terra, however, takes it to a whole new level. Among its capabilities, ASTER collects pairs of slightly offset images of Earth's surface. The image pairs work like our eyes – the slightly offset images give information about depth and allow scientists to visualize the Earth's terrain in 3D. The first Global Digital Elevation Model was released in 2009, stitched together from of 1.3 million scenes of the land surface. No more piecing together maps made by different people in different eras, it was the highest resolution topographic map, which covered 90 percent of Earth's surface consistently from nearly pole-to-pole. Scientists use elevation data to understand how the land changes over time, especially from natural disasters like landslides, earthquakes, floods, and tsunamis.

When tiny plants in the ocean bloom, they bloom for hundreds of miles. Phytoplankton, the base of the marine food chain, explode in population when cold, nutrient-rich waters from rivers or the deep ocean rise and mix with sun-lit surface waters. Globally, phytoplankton blooms account for about half of the net photosynthesis on Earth and are major players in taking carbon out of the atmosphere and transferring it to the ocean. With the bloom comes a feeding frenzy, as fish and marine mammals flock to the microscopic feast that supports their populations that in turn support the human demand for fish. Daily ocean color measurements from the MODIS instruments aboard the Terra and Aqua satellites have dramatically changed scientists' understanding of the complex biological and physical relationships between phytoplankton, marine ecosystems, and the global carbon budget.

Carbon monoxide is a colorless, odorless pollutant that emerges from wildfires, vehicle tailpipes and other human sources. Once in the atmosphere it is one of the ingredients for ground-level ozone, a harmful pollutant that contributes to smog – sometimes thousands of miles from where the carbon monoxide originated. An instrument on Terra called Measurements of Pollutants in the Troposphere, or MOPITT, was the first dedicated to tracking sources of carbon monoxide and following the gas across the globe. And the news is good. With MOPITT data, combined with data from the Atmospheric Infrared Sounder, or AIRS, on Aqua and the Tropospheric Emissions Spectrometer, or Tes, on Aura, as well as European satellite data, scientists have found that carbon monoxide emissions have declined at a rate of one percent per year since 2000.

Taking a full photograph of Earth from space takes some doing. In 2002, NASA scientists and visualizers stitched together strips of brand new data, in natural color, collected over four months from the Moderate Resolution Imaging Spectroradiometer, or MODIS, instrument aboard Terra and then they added a layer of clouds – creating this composite Blue Marble that became one of the most iconic Earth images ever.