The Blue Marble

thumb|upright=1.2|The Blue Marble, taken by [[Harrison Schmitt of the Apollo 17 crew in 1972. The original photograph was taken with the South Pole facing the top; however, cropped, rotated, and processed versions are the most commonly used, like this one.|right]]

The Blue Marble is a photograph of Earth taken on December 7, 1972, by Harrison Schmitt aboard the Apollo 17 spacecraft on its way to the Moon. Viewed from around from Earth's surface, a cropped, rotated, and processed version has become one of the most reproduced images in history.

Background

The Blue Marble was not the first clear color image taken of an illuminated face of Earth, since such images by satellites had already been made and released as early as 1967. Apollo 17 was the second mission to include such a photo taken by a human, after the 1968 photograph Earthrise taken by William Anders of Apollo 8.

Before the Blue Marble a picture of the fully illuminated Earth by the ATS-3 satellite was used in 1968 by Stewart Brand for his Whole Earth Catalog, after campaigning since 1966 to have NASA release a then-rumored satellite image of the entire Earth as seen from space. He got inspired during an LSD trip, seeing a "psychedelic illusion" of the Earth's curvature, convincing him that a picture of the entire planet would change how humans related to it. He sold and distributed buttons for 25 cents each that asked: "Why haven't we seen a photograph of the whole Earth yet?" During this campaign, Brand met Buckminster Fuller, who offered to help Brand with his project. Several of the pins made their way to NASA employees.

The astronauts had the Earth's South Pole facing upwards and the Sun above them (in spatial navigation terms, to their zenith) when they took the image. To the astronauts, the Earth had the appearance and size of a glass marble.

At that time, Africa was in noon and shows many weather systems, featuring a Shapyro–Keyser cyclone near to the center of the image. Cyclone Sixteen (16B) can be seen in the upper right of the image. This storm had brought flooding and high winds to the Indian state of Tamil Nadu on December 5, two days before the photograph was taken.

According to the photograph description by NASA it was taken at 05:39 a.m EST (10:39 UTC), 5 hours 6 minutes after launch of the Apollo 17 mission, Alternatively, Eric Hartwell has identified it as having been taken slightly earlier at 5 hours 3 minutes, when one crew member states having changed the f-number, presumably between AS17-148-22725, the first of the series of photos, and the following less exposed images like The Blue Marble. It is the third of a series of shots which were taken just before and are nearly identical, NASA photograph AS17-148-22725 and AS17-148-22726, the second also having been used as a full-Earth image.

The widely published versions are cropped, rotated with south pointing up relative to the capsule, and chromatically adjusted from the original photographs.

Authorship

NASA generally credits images to the whole crew of a mission. However, interviews For example, in 2013, Schmitt gave a phone interview for the website The Phoblographer in which he explained some of the camera settings, and recalled that the reason the photograph was taken stemmed from his hobby as an amateur meteorologist, with weather prediction being a personal mission goal; Schmitt did not anticipate the image's popular acclaim.

Processing

thumb|A side-by-side comparison of different white-balanced Blue Marble images.

The original camera film was rescanned in 2007 by the Arizona State University (ASU) for their Apollo Image Archive, producing an extremely high resolution raw version.

Legacy

As speculated by NASA archivist Mike Gentry, The Blue Marble is among the most widely distributed images in history.

thumb|The 1973 version of the [[Earth Flag, proposed by John McConnell using the Blue Marble]]

The phrase "blue marble" (as well as the picture itself) is frequently used, as in the Earth flag by environmental activist organizations or companies attempting to promote an environmentally conscious image.

Poet-diplomat Abhay Kumar penned an Earth anthem inspired by the Blue Marble which contains "all the peoples and the nations of the world, one for all, all for one, united we unfurl the blue marble flag".

Other references

The image has been used to validate state-of-the-art atmospheric reanalysis fifty years after it was taken.

There has also been a children's television program called Big Blue Marble.

Subsequent Blue Marble images

Subsequent similar images of Earth (including composites at much higher resolution) have also been termed Blue Marble images.

Blue Marble 2000

thumb|Blue Marble 2000. [[Hurricane Linda (1997)|Hurricane Linda can be seen off the coast of Mexico.]]

In 2000, there was a so-called Blue Marble 2000 image released. It was based on data from 1997 by the Geostationary Operational Environmental Satellite (GOES), Sea-viewing Wide Field-of-view Sensor (SeaWiFS) satellite and Polar Operational Environmental Satellites (POES), complemented with a digital elevation model from the U.S. Geological Survey.

Blue Marble 2002

thumb|Blue Marble composite images generated by NASA in 2002, based on data from 2001.

In 2002, NASA released an extensive set of satellite-captured imagery, including prepared images suitable for direct human viewing, as well as complete sets suitable for use in preparing further works. At the time, 1 km/pixel was the most detailed imagery available for free, and permitted for reuse without a need for extensive preparatory work to eliminate cloud cover and conceal missing data, or to parse specialized data formats. The data also included a similarly manually assembled cloud-cover and night-light image sets, at lower resolutions. One image was used as one of the default wallpapers for the first-generation iPhone in 2007.

Blue Marble Next Generation (2005)

thumb|[[NASA Earth Observatory animation called Blue Marble Next Generation (2005), showing Earth in 2004.]]

A subsequent release was made in 2005, named Blue Marble Next Generation. This series of digital image mosaics was produced with the aid of automated image-sifting upon images from NASA's Earth Observatory, which enabled the inclusion of a complete, cloud-free globe for each month from January to December 2004, at even higher resolution (500 m/pixel). The original release of a single-image set covering the entire globe could not reflect the extent of seasonal snow-and-vegetative cover across both hemispheres, but this newer release closely modeled the changes of the seasons.

A number of interactive viewers for these data have also been released, among them a music visualization for the PlayStation 3 that is based on the texture data.

Blue Marble 2007

Based on data from multiple satellites, from different times, were put together by a team of NASA merging layers of global data about every type of layer of features, from oceanic to atmospheric, to create the Blue Marble 2007.

Blue Marble 2012

thumb|Blue Marble 2012 – a composite satellite image.

On January 25, 2012, NASA released a composite image of the Western Hemisphere of Earth titled Blue Marble 2012. Robert Simmon is most notable for his visualization of the Western Hemisphere. The picture logged over 3.1 million views on the Flickr image hosting website within the first week of release. On February 2, 2012, NASA released a companion to this new Blue Marble, showing a composite image of the Eastern Hemisphere from data obtained on January 23, 2012. The data was obtained from six orbits of the Earth by the Suomi NPP over an eight-hour period. during an annual meeting of Earth scientists held by the American Geophysical Union in San Francisco. The images display all the human and natural matter that glows and can be detected from space. The data was acquired by the Suomi NPP satellite in April and October 2012 and then mapped over existing Blue Marble imagery of Earth to provide a realistic view of the planet. The Suomi NPP satellite completed 312 orbits and gathered 2.5 terabytes of data to get a clear shot of every parcel of the Earth's land surface. Named for satellite meteorology pioneer Verner Suomi, the satellite flies over any given point on Earth's surface twice each day and flies above the surface in a polar orbit.

The nighttime views were obtained with the new satellite's "day-night band" of the Visible Infrared Imaging Radiometer Suite (VIIRS), which detects light in a range of wavelengths from green to near-infrared, and uses filtering techniques to observe dim signals such as city lights, gas flares, auroras, wildfires, and reflected moonlight. Auroras, fires, and other stray light have been removed in the case of the Black Marble images to emphasize the city lights. The image was taken on July 6, 2015. The photograph, of the Western Hemisphere, is centered over Central America. The Western United States, Mexico and the Caribbean are visible, but much of South America is hidden beneath cloud cover. Greenland can be seen at the upper edge of the image.

The EPIC science team plans to upload 13 new color images per day on their website. The color balance has been adjusted to approximate an image that could be seen with the average human eye. In addition to images, scientific information will be uploaded as it becomes available after in-flight calibration is complete. The science information will be ozone and aerosol amounts, cloud reflectivity, cloud height, and vegetation information. The EPIC instrument views the Earth from sunrise in the west to sunset in the east 12 to 13 times per day as the Earth rotates at 15 degrees of longitude per hour. Clearly visible are storms forming over the Atlantic and Pacific Oceans, major slowly moving "cloud rivers", dust aerosol plumes from Africa, the Sun's reflection in the oceans, ship exhaust tracks in the clouds, rivers and lakes, and the variegated land surface patterns especially in the African deserts. The spatial resolution of the color images is about 10 km (6 miles), and the resolution of the science products will be about 20 km (10 miles). Once every three months, lunar images are obtained that are the same as those viewed from Earth during a full Moon. On occasion, the other side of the Moon will appear in the Earth images as the Moon crosses in front of the Earth.