Abalos Undae
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Abalos Undae is a dune field on Mars in the periphery of Planum Boreum, the Martian North pole. It is one of the officially named northern circumpolar dune fields, along with Olympia, Hyperboreae, and Siton Undae, and also one of the densest of the region. Its northernmost boundary is located in the southwest channel that separates the Abalos Colles formation from the main polar ice cap, and from there the dune field extends southwest all the way to the lowlands of Vastitas Borealis.
Abalos Undae dunes at Abalos Scopuli, the scarp of Abalos Mensa. The ice layers on the cap and basal formations are also visible. The picture was taken by the HiRISE camera on board the Mars Reconnaissance Orbiter and was enhanced by NASA in RGB colour.
Abalos Undae at Abalos Scopuli, the scarp of Abalos Mensa
Dunes in Abalos Undae. The blue areas indicate the presence of dunes of basaltic origin, while the light-colour areas are probably dust.
Gypsum deposits in the dunes of Abalos Undae
Olympia Undae
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Olympia Undae is a vast dune field in the north polar region of the planet Mars. It consists of a broad "sand sea" or erg that partly rings the north polar plateau from about 120° to 240°E longitude and 78° to 83°N latitude. Stretching about 1,100 km (680 mi) across and covering an area of 470,000 km2, Olympia Undae is the largest continuous dune field on Mars. It is similar in size to the Rub' Al Khali in the Arabian Peninsula, the largest active erg on Earth.
Olympia Undae dunes, as seen by HiRISE. Two sets of transverse dunes are visible, indicating varying wind direction. Olympia Undae is also known as the North Polar Erg.
Closeup, color-enhanced image of Olympia Undae dunes with melting/subliming ice-cap fragments. Note Barchan dunes and patterned ground. Width of image is about 1 km/3000 ft.
CRISM spectral signal for gypsum (polyhydrated sulfates) in Olympia Undae dunes.