Open AccessGround ice at the Phoenix Landing Site: Stability state and origin
Author(s) -
Mellon Michael T.,
Arvidson Raymond E.,
Sizemore Hanna G.,
Searls Mindi L.,
Blaney Diana L.,
Cull Selby,
Hecht Michael H.,
Heet Tabatha L.,
Keller H. Uwe,
Lemmon Mark T.,
Markiewicz Wojciech J.,
Ming Douglas W.,
Morris Richard V.,
Pike W. Thomas,
Zent Aaron P.
Publication year - 2009
Publication title -
journal of geophysical research: planets
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.67
H-Index - 298
eISSN - 2156-2202
pISSN - 0148-0227
DOI - 10.1029/2009je003417
Subject(s) - geology , ice divide , regolith , antarctic sea ice , geomorphology , pancake ice , melt pond , arctic ice pack , soil water , sea ice thickness , ice shelf , sea ice , atmospheric sciences , cryosphere , astrobiology , soil science , climatology , physics
A primary objective of the Phoenix mission was to examine the characteristics of high latitude ground ice on Mars. We report observations of ground ice, its depth distribution and stability characteristics, and examine its origins and history. High latitude ground ice was explored through a dozen trench complexes and landing thruster pits, over a range of polygon morphological provinces. Shallow ground ice was found to be abundant under a layer of relatively loose ice‐free soil with a mean depth of 4.6 cm, which varied by more than 10x from trench to trench. These variations can be attributed mainly to slope effects and thermal inertia variations in the overburden soil affecting ground temperatures. The presence of ice at this depth is consistent with vapor‐diffusive equilibrium with respect to a mean atmospheric water content of 3.4 × 10 19 m −3 , consistent with the present‐day climate. Significant ice heterogeneity was observed, with two major forms: ice‐cemented soil and relatively pure light toned ice. Ice‐cemented soils, which comprised about 90% of the icy material exposed by trenching, are best explained as vapor deposited pore ice in a matrix supported porous soil. Light toned ice deposits represent a minority of the subsurface and are thought to consist of relatively thin near surface deposits. The origin of these relatively pure ice deposits appears most consistent with the formation of excess ice by soil ice segregation, such as would occur by thin film migration and the formation of ice lenses, needle ice, or similar ice structures.