“blebby” Terrain and Domes on the Northern Plains of Mars: Evidence of Ancient Ice Ages?

Introduction: In recent years, a number of researchers have recognized signs of past glacial activity on Mars and features that could be extant rock glaciers [1,2]. There has also been the recognition of " pasted on " terrains which are interpreted as dust-covered snow or ice deposits [3]. Many of these features are attributed to relatively recent (within the last several million years) periods of high obliquity that led to Martian ice ages [4]. A reasonable question is what evidence might exist for more ancient ice ages? Unusual Northern Plains Terrain: We have un-dertaken an examination of unusual terrains and land-forms on the northern plains of Mars, focusing primarily Utopia and Acidalia Planitiae and their surroundings [5]. Among the unusual terrains that we have recognized is what we call " blebby terrain " , an example of which is provided in Fig. 1. Examples of the terrain that we have been examining occur on the western border of Utopia Planitia. The example in Fig. 1 is at 44° N, 67° E. As is shown in Fig. 1b, the terrain is bright in nighttime THEMIS images relative to the background. Thermal inertia (TI) values extracted from the THEMIS data [6] indicate that the higher TI portions of the terrain reach values on the order of 700 J/m