2002 Annual Science Report
Arizona State University Reporting | JUL 2001 – JUN 2002
Nanoscale Minerals as Biomarkers
The most recent, and the strongest, cases for the biogenic origin of some of the magnetite crystals in Martian meteorite ALH 84001 is their supposed identity to those produced by the terrestrial magnetotactic bacteria of strain MV-1. The shape of these nanocrystals is one of the several characteristics contributing to this suggested identity. We have undertaken an ambitious program to use advanced methods of transmission electron microscopy to determine these shapes more precisely than was previously possible. For this purpose we are using electron holography and electron tomography, both of which provide significantly more 3-dimensional details than standard electron microscopy. We showed (Buseck et al., 2001) that the shapes of the crystals are known in far less detail than had been reported. On that basis we concluded that existing data are of insufficient quality to support the reported identity of meteoritic and biogenic crystals – their shapes were simply not sufficiently accurately known, a result we confirmed by subsequent work and reported in March at the Lunar and Planetary Science Conference (LPSC) (Weyland et al., 2002).
Work is progressing vigorously. We are currently machining a newly designed sample holder for the transmission electron microscopy (TEM) that will allow tilts over even greater angles, resulting in yet greater tomographic detail and accuracy. We have also spent much time developing rapid, robust phase unwrapping algorithms that can be relied on to operate automatically. Such algorithms will be essential for mass processing of tomographic holograms.
PROJECT MEMBERS:Peter Buseck
RELATED OBJECTIVES:Objective 8.0
Search for evidence of ancient climates, extinct life and potential habitats for extant life on Mars.