Abalos Undae is a dune field on Mars, in the periphery of Planum Boreum, the Martian north pole. It is a part of the northern circumpolar dune fields, along with Olympia, Hyperboreae, and Siton Undae, which are officially named after nearby classical albedo features. It is located in the southwest channel that separates the Abalos Colles formation remnant from the main ice cap, and continues all the way to the channel's southern boundary. The dunes of the Abalos field may have formed from erosion of Rupes Tenuis, the polar scarp. Abalos Undae has its northernmost boundary in the neighbourhood of Abalos Mensa and continues in a southwestward direction after it emerges from the western end of a narrow channel separating Rupes Tenuis from Abalos Mensa. Enhanced colour images obtained by the High Resolution Imaging Science Experiment camera on board the Mars Reconnaissance Orbiter highlight the areas of the dunes where different materials are present. The blue areas indicate the presence of dunes of basaltic origin, while the light-colour areas are probably dust. The pictures are of sufficient resolution to show ripples on the dune surface. The ripples are generated by winds, as are the dunes. The dunes are considered stationary as a unit, with only small ripple movements present. Similarly to the rest of the dune fields around the periphery of Planum Borealis, the Abalos dune field is considered to consist of lag deposits resulting from the ablation of the sediment found in basal units. The Abalos dune field is considered one of the densest dune fields in the northern circumpolar region of Mars. Other fields of similar density in the region include the Olympia, Hyperboreae, and Siton Undae. The Abalos dune field consists of transverse dune linear sequences that, overall, form platforms of sand ranging from approximately 10 metres to 200 metres thickness. Abalos Undae, along with Hyperboreae and Siton Undae, is a sand tributary to mostly medium-density sand fields located east of Olympia Undae and extending to the prime meridian of Mars. Image analysis, performed using the method of spectral derivatives, indicates that Abalos Undae, and the rest of the densest dunes fields in the periphery of Planum Borealis, Olympia Undae and Hyperboreae Undae, show the highest pixel density indicating the presence of gypsum. The gypsum of Abalos Undae may be eroding due to scouring action by substrates of bedrock involved in plains formation.
