European Space Agency Flickr Update

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Rub al Khali
20-05-2016 10:17 AM CEST

europeanspaceagency posted a photo:

Rub al Khali

Rolling sand dunes in the expansive Rub’ al Khali desert on the southern Arabian Peninsula are pictured in this image from the Sentinel-2A satellite.

Also known at the ‘Empty Quarter’, the Rub’ al Khali is the largest contiguous sand desert in the world. Precipitation rarely exceeds 35 mm a year and regular high temperatures are around 50°C.

The yellow lines and dots in this false-colour image are sand dunes. Looking closer at the dunes in the lower right, many have three or more ‘arms’ shaped by changing wind directions and are known as ‘star dunes’. They tend to ‘grow’ upwards rather than laterally, and reach up to 250 m in height in some parts of the Rub’ al Khali.

The dunes are interspersed with hardened flat plains – remnants of shallow lakes that existed thousands of years ago, formed by monsoon-like rains and runoff. The multispectral instrument on Sentinel-2 uses parts of the infrared spectrum to detect subtle changes in vegetation cover, but can also see changes in mineral composition where vegetation is sparse. In this image, shades of brown to bright purple show the mineral composition, possibly including salt or gypsum.

This image – also featured on the Earth from Space video programme – was captured by Sentinel-2A on 22 December 2015. The satellite is the first in the two-satellite Sentinel-2 mission for Europe’s Copernicus programme, and carries a wide-swath high-resolution multispectral imager with 13 spectral bands for a new perspective of our land and vegetation.

Credit: Contains modified Copernicus Sentinel data [2016], processed by ESA

Mars in opposition 2016
20-05-2016 09:18 AM CEST

europeanspaceagency posted a photo:

Mars in opposition 2016

This image shows our neighbouring planet Mars, as it was observed shortly before opposition in 2016 by the NASA/ESA Hubble Space Telescope.

Some prominent features of the planet are clearly visible: the ancient and inactive shield volcano Syrtis Major; the bright and oval Hellas Planitia basin; the heavily eroded Arabia Terra in the centre of the image; the dark features of Sinus Sabaeous and Sinus Meridiani along the equator; and the small southern polar cap.

Read more: Close up of the red planet

Credit: NASA, ESA, the Hubble Heritage Team (STScI/AURA), J. Bell (ASU), and M. Wolff (Space Science Institute)

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