On August 25, 2000, the
Moderate-resolution Imaging Spectroradiometer (MODIS) acquired this
spectacular image of a region in Africa's Sahara Desert, including the
southern part of the border between Algeria and Libya. Three large rock
massifs appear to be pushing up from beneath red sand dunes: from left
to right are the Tassili, Tadrart-Acacus, and Amsak massifs. Different
rock types account for rock colors varying from dark brown (Acacus) to
the pale tone of Amsak eastern portion (Amsak Mellet means Pale Amsak in
the local Tuareg dialect).
The dendritic structures of ancient riverbeds are clearly visible in the
Acacus-Amsak region. Multidisciplinary studies (including
paleo-climatology and paleo-botany) suggest that this area was wet
during the last glacial era, covered by forests and populated by wild
animals. On the same rocks, archaeologists have found a large number of
rock paintings and engravings, faint tracks of one of the most ancient
civilizations of the world. Starting about 12,000 years ago, the
hunters rapidly learned domestication of buffalo and goat, and developed
one of the first systems of symbolic art. Extremely dry weather
conditions began here about 5,000 years ago, perhaps leading to the
decline of this civilization but helping to preserve their ancient
masterpieces.
This natural color image (top) was produced using three MODIS bands
corresponding to red, green, and blue wavelengths. The ground resolution
is 250 meters per pixel and was made by "injecting" the high-resolution
red channel into lower resolution green and blue channels. The image
was processed by Telespazio's Earth Observation division, in its new
products development facility in Rome, Italy. The MODIS sensor flies
aboard NASA's Terra spacecraft, launched in December 1999.
Image courtesy Luca Pietranera, Telespazio, Rome, Italy