Reuters/San Francisco

Almost 40 years to the day after the Apollo 17 crew snapped the famed “blue marble” image of Earth floating in space on December 7, 1972, Nasa has unveiled “black marble” video views of the planet by night.
The cloud-free pictures, taken with a high-resolution visible and infrared imager aboard a Nasa and National Oceanic and Atmospheric Administration (NOAA) satellite, capture the night lights of Earth in unprecedented detail.
The sensor can capture the equivalent of three low-light images simultaneously, giving researchers the opportunity to study Earth’s atmosphere, land and oceans at night.
“It’s very high-quality data,” NOAA scientist Christopher Elvidge told reporters at the American Geophysical Union conference in San Francisco. “I rate it six times better spatial resolution.”
The so-called day-night band of the Visible Infrared Imaging Radiometer Suite, or VIIRS, can distinguish the night-time glow of Earth’s atmosphere as well as a light from a single ship at sea. The resolution is far sharper than what has been available previously.
VIIRS is aboard the Suomi NPP satellite, which orbits about 800km above Earth’s poles.
The data was acquired over nine days in April 2012 and 13 days in October 2012. It took the satellite 312 orbits and 2.5 terabytes of data to get a clear shot of every parcel of Earth’s land surface and islands. This new data was then mapped over existing Blue Marble imagery to provide a realistic view of the planet.
Scientists used the day-night sensor to watch the superstorm Sandy, illuminated by moonlight, hit the New Jersey shore on October 29.
It also captured the power outages that plunged the area into darkness as the storm tore into populated areas.
The National Weather Service is starting to use the VIIRS day-night sensor to forecast fog in coastal regions, including San Francisco.
Some VIIRS images have surprised scientists. The sensor, for example, captured light from the upper atmosphere illuminating clouds and ice in visible wavelengths – by night.