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Mars Pathfinder Science


The Tale of Barnacle Bill

Barnacle Bill was the first target for investigation which resulted in the discovery of andesitic material on Mars. Although the APXS data does indicate a minearalogical composition consistent with volcanic andesite the rough surface texture of bill suggests it could be a breccia which is composed of many different fragments of rock that combine to give an overall similar chemical composition. This hypothesis can be tested via reflectance spectroscopy. Namely

To this this hypothesis the following areas on Bill were selected for spectroscopy:

and the resulting spectra are shown below

The basic result is that the spectra show only two types:

The spectra are therefore more consistent with the andesite explanation for Bill rather than it being a breccia. If it is a breccia, then the heterogenous nature must occur on a finer scale (e.g. less than 1 cm) than is probed by the spot spectrometer.


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