File:Aorounga Impact Crater, Chad.jpg

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English: The concentric ring structure of the Aorounga crater—renamed Aorounga South in the multiple-crater interpretation of SIR data—is clearly visible in this detailed astronaut photograph. The central highland, or peak, of the crater is surrounded by a small sand-filled trough; this in turn is surrounded by a larger circular trough. Linear rock ridges alternating with light orange sand deposits cross the image from upper left to lower right; these are called yardangs by geomorphologists. Yardangs form by wind erosion of exposed rock layers in a unidirectional wind field. The wind blows from the north-east at Aorounga, and sand dunes formed between the yardangs are actively migrating to the south-west.


International Space Station InsigniaISS Crew Earth Observations: ISS020-E-26195International Space Station Insignia
Identification
Mission ISS020 (Expedition 20)
Roll E
Frame 26195
Country or Geographic Name CHAD
Features AOROUNGA IMPACT CRATER, YARDANGS
Center Point Latitude 19.1° N
Center Point Longitude 19.2° E
Camera
Camera Tilt 42°
Camera Focal Length 800 mm
Camera Nikon D3
Film 4256 x 2832 pixel CMOS sensor, 36.0mm x 23.9mm, total pixels: 12.87 million, Nikon FX format.
Quality
Percentage of Cloud Cover 0-10%
Nadir What is Nadir?
Date 2009-07-25
Time 10:57:33
Nadir Point Latitude 21.5° N
Nadir Point Longitude 20.7° E
Nadir to Photo Center Direction Southwest
Sun Azimuth 242°
Spacecraft Altitude 187 nautical miles (346 km)
Sun Elevation Angle 86°
Orbit Number 1198
Original image caption
Aorounga Impact Crater, Chad

Aorounga Impact Crater is located in the Sahara Desert, in north-central Chad, and is one of the best preserved impact structures in the world. The crater is thought to be middle or upper Devonian to lower Mississippian (approximately 345–370 million years old) based on the age of the sedimentary rocks deformed by the impact. Spaceborne Imaging Radar (SIR) data collected in 1994 suggests that Aorounga is one of a set of three craters formed by the same impact event. The other two suggested impact structures are buried by sand deposits.

The concentric ring structure of the Aorounga crater—renamed Aorounga South in the multiple-crater interpretation of SIR data—is clearly visible in this detailed astronaut photograph. The central highland, or peak, of the crater is surrounded by a small sand-filled trough; this in turn is surrounded by a larger circular trough. Linear rock ridges alternating with light orange sand deposits cross the image from upper left to lower right; these are called yardangs by geomorphologists. Yardangs form by wind erosion of exposed rock layers in a unidirectional wind field. The wind blows from the northeast at Aorounga, and sand dunes formed between the yardangs are actively migrating to the southwest.

Date
Source NASA Earth Observatory
Author
  • NASA Expedition 20 crew
  • Image Science & Analysis Laboratory, NASA Johnson Space Center
Other versions
  • Version with alternate grading, corrected vignette and higher resolution
    Version with alternate grading, corrected vignette and higher resolution
This image or video was catalogued by Johnson Space Center of the United States National Aeronautics and Space Administration (NASA) under Photo ID: ISS020-E-026195.

This tag does not indicate the copyright status of the attached work. A normal copyright tag is still required. See Commons:Licensing.
Other languages:

العربية ∙ беларуская (тарашкевіца) ∙ български ∙ català ∙ čeština ∙ dansk ∙ Deutsch ∙ English ∙ español ∙ فارسی ∙ français ∙ galego ∙ magyar ∙ հայերեն ∙ Bahasa Indonesia ∙ italiano ∙ 日本語 ∙ македонски ∙ മലയാളം ∙ Nederlands ∙ polski ∙ português ∙ русский ∙ sicilianu ∙ slovenščina ∙ Türkçe ∙ українська ∙ 简体中文 ∙ 繁體中文 ∙ +/−

Image acquired with a Nikon D3 digital camera fitted with an 800 mm lens, and is provided by the ISS Crew Earth Observations experiment and Image Science & Analysis Laboratory, Johnson Space Centre.

Licensing[edit]

Public domain This file is in the public domain in the United States because it was solely created by NASA. NASA copyright policy states that "NASA material is not protected by copyright unless noted". (See Template:PD-USGov, NASA copyright policy page or JPL Image Use Policy.)
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current09:02, 10 August 2009Thumbnail for version as of 09:02, 10 August 20091,440 × 960 (472 KB)Originalwana (talk | contribs){{Information |Description={{en|1=The concentric ring structure of the Aorounga crater—renamed Aorounga South in the multiple-crater interpretation of SIR data—is clearly visible in this detailed astronaut photograph. The central highland, or peak, of

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