PYTi-NiCr SIGNATURES IN THE COLUMBIA HILLS ARE PRESENT IN CERTAIN MARTIAN

Introduction: Uniquely high levels of phosphorus and titanium were observed in several samples [1-3] by the APXS x-ray fluorescence measurements as the MER Spirit rover climbed Husband Hill (Columbia Hills, Gusev crater, Mars). A careful study of many such samples and their geochemical variability has revealed additional elements in this pattern, and that the derived multi-element signature is also unambigu-ously manifested in several martian meteorites. The Signature in Husband Hills Samples: The Wishstone and Watchtower classes of rocks [2-3] both contain elevated P and Ti, with Wishstone being the first type specimen encountered, prior to midway up Husband Hill. Samples in this class can contain >5 % P 2 O 5 and up to 3 % TiO 2. It was also noticed early-on that these materials are very low in Cr. Independence class samples have also been reported to contain high P and Ti [4]. Comparisons are shown in Figure 1. Several new samples, including some at the summit and beyond but not yet allocated to classes, also contain these enhancements. An unexpected occurrence of yttrium at a detectable level led to a search for Y in other samples. It is found that the Y correlates positively with P, Figure 2, a common geochemical occurrence. It was also found that for these low-Cr materials, the Ni is often also lower (<100 ppm) than typical and correlates linearly with the Cr. We have therefore identified an association of high P, Y and Ti, coupled with low Ni and Cr. In addition, these materials tend to have less Fe, less Mg and more K than other martian samples. The Signature in Martian Meteorites: Although lower by about a factor of 2 in P 2 O 5 content, the martian meteorite QUE 94201 not only exhibits high P, as noted by [3, 5, and others], but all the characteristics of the PYTi-NiCr signature, compared to classical SNCs (see element tabulations by Lodders [8]). The same is true of the Los Angeles meteorite and for lithology B of EETA79001 (but not lithology A). Figure 3 compares P, Ti and Cr contents of these and other martian meteorites. Other elements expected to be at higher levels, from meteorite analyses, include Al and especially Ga and some heavy REE. Implications: Connections between classes of rocks at Husband Hill, and most importantly the analogous samples available for study on Earth, have important potential consequences for further study.