Planetary Ground Penetrating Radar
Ground-penetrating radar (GPR) gathers information on subsurface features using radio waves that are transmitted into the subsurface that then reflect off differing layers and structures. The successful utilization of GPR in Bir Kiseiba, Egypt, a terrestrial location with many similarities to Martian terrains, helps to set the context for future planetary application of the instrument. A planetary model of a GPR, called STRATA, has been devised and was proposed for the Mars Science Laboratory mission, but not selected.
GPR is a non-invasive instrument that can supplement or substitute for activities like drilling used to determine information about features below the ground. Depending on the frequency applied, different depths up to several 10's of meters can be explored. Lower frequencies result in better penetration, but lower resolution. Higher frequencies produce better resolution and less penetration1. GPR is primarily used for the detection of features, especially those that can assist in understanding a region’s past history, such as buried fluvial channels beneath a contemporary desert as exemplified in Bir Kiseiba, Egypt.
Extreme aridity in Egypt enhances the capability of radar to distinguish geologically distinct layers. In Bir Kiseiba, three different layers were distinguished to the ground surface, wind blown sediments, soils produced by running water, and bedrock all produced unique reflections detected by the radar. Though the Sahara desert and dry surfaces on Mars have different climate histories and mineralogical compositions2, researchers expect the surfaces may respond similarly to the radar. Buried water systems can be revealed 10 to 15 m deep on Earth2 and it is expected that they can likewise be revealed on Mars.
It is this assumption that STRATA, the proposal for GPR on the Mars Science Laboratory (MSL), was grounded in. Assessing habitability and aqueous history of a region on Mars are main objectives of the MSL mission. The STRATA instrument would use a 400-MHz impulse to define stratigraphy at a spacial resolution of tens of centimeters to 10-15 m depth1. The application of GPR would focus on locating, recording, and assessing the history of aqueous deposition, as well as providing the context for other MSL instruments to assess the biological potential of the areas under investigation1. For more information visit the MSL home page.
1. Grant, J. A., C. J. Leuschen, A. E. Schultz, J. Rudy, R. S. Bokulic, and K. K. Williams (2005), STRATA: Ground penetrating radar for Mars rovers, Workshop on Radar Investigations of Planetary and Terrestrial Environments, Abstract 6009, Houston, TX.
2. Grant, J. A., T. A. Maxwell, A. K. Johnston, A. Kilani, and K. K. Williams (2004), Documenting drainage evolution in Bir Kiseiba, southern Egypt: Constraints from ground-penetrating radar and implications for Mars, J. Geophys. Res., 109, E09002, doi:10.1029/2003JE002232.
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