(Left) Preliminary rock and soil analyses. In this diagram, preliminary Alpha Proton X-Ray Spectrometer analyses of soils (small circles) extend the range of Viking soil analyses. Rock analyses are indicated by stars. The analysis of Yogi appears to be contaminated by dust adhering to the rock's surface. The rock composition can be estimated by subtracting a portion of dust; the resulting Yogi composition is very similar to that of Barnacle Bill (assuming 50% dust having the composition of drift analysis A-5 and using a linear mixing model to subtract the dust, which is only strictly valid if the dust, where present, is thicker than the APXS penetration depth). Barnacle Bill is also contaminated by dust, but to a lesser extent.
(Right) Preliminary X-ray data illustrates chemical differences between terrestrial rocks and meteorites inferred to have come from Mars. The martian meteorites (as well as Viking soil analyses) all plot to the left of the fields for Earth rocks. Pathfinder APXS analyses of rocks (stars) and soils (small circles) appear to plot in the gap between these previously defined fields, although they are similar to at lease one basaltic meteorite. The other two stars represent the compositions of Barnicle Bill and Yogi.

Images and data are from the Pathfinder Web site (or mirrors) that can be reached at http://mpfwww.jpl.nasa.gov. Educators can obtain a set of Mars Pathfinder images as well as a poster with classroom activities by contacting NASA CORE at 440-774-1051, ext. 249 or 293, or via e-mail to nasaco@leeca8.leeca.ohio.gov. See also the Web site at http://spacelink.nasa.gov/CORE.