Planetary and Space Science 5 r

• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Subjects: Mars; Past climate; Permafrost; Cryoplanation; permafrost
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.547.7204; http://www.planetary.brown.edu/pdfs/3229.pdf

and mid-latitude surface processes 10Ma ago. Conditions favoring an active layer are not predicted to be common in the next 10Ma. The much higher obliquity excursions 1973; Pewe, 1991), where the year-average surface tem-perature is below the water freezing point (e.g., Williams hundreds of meters thick (e.g., Brown, 1970). The upper meter(s)-thick layer of the ground in permafrost regions can undergo a yearly freezing and thawing cycle; this is ARTICLE IN PRESSknown as the active layer (Fig. 1) (Miller and Black, 2003). In the spring, a thawing wave propagates downwards into the permafrost and in the fall and early winter, a freezing