Author's School

Graduate School of Arts & Sciences

Author's Department/Program

Earth and Planetary Sciences

Author's Department/Program

Earth and Planetary Sciences


English (en)

Date of Award


Degree Type


Degree Name

Master of Arts (MA)

Chair and Committee

Raymond Arvidson


The Phoenix Lander touched down on the northern distal flank of the shield volcano Alba Patera in a ~150 km wide valley underlain by the Scandia Formation. The geomorphology and geology of the landing site is dominated by the ~0.6 Ga, 11.5 km wide, bowl-shaped impact crater, Heimdal, and its areally extensive ejecta deposits. The Lander is located ~20 km to the west of the crater and is sitting on a plains surface underlain by partially eroded Heimdal ejecta deposits. Heimdal was produced by a hypervelocity impact into fine-grained, ice-rich material and is inferred to have produced high velocity winds and a ground-hugging ejecta emplacement mode that destroyed or buried preexisting surfaces and rock fields out to ~10 crater radii. Patterned ground is ubiquitous, with complex polygon patterns and rock rubble piles located on older plains: ~3.3 Ga) to the west of the ejecta deposits. Crater size frequency distributions are complex and represent equilibria between crater production and destruction processes: e.g., aeolian infill, cryoturbation, relaxation of icy substrate). Rock abundances increase near craters for the older plains and rocks with their dark shadows explain the reason for the few percent lower albedo for these plains as opposed to the Heimdal ejecta deposits. Many rocks at the landing site have been reworked by cryoturbation and moved to polygon troughs. The evidence for cryoturbation and the lack of aeolian features imply that the soils sampled by Phoenix are locally derived and mixed with a subordinate amount of wind-blown dust.


Permanent URL: