2000 Annual Science Report
NASA Jet Propulsion Laboratory Reporting | JUL 1999 – JUN 2000
Fractionation of Transition Metal Isotopes
The primary focus of this research is to determine if fractionations of transition metal isotopes can be used as biomarkers. We are also interested in the possible use of such fractionations to study changes in metal geochemical cycling through time, which could provide insight into past changes in environmental conditions and/or changing use of metals in biochemistry. The biomarker applications are of primary interest to the JPL/Caltech Team. The other applications are also of interest to the Harvard Team, which also supports this research.
In Year 1 and 2, most of our focus was on methods development and initial applications, with iron and molybdenum isotopes getting the bulk of attention. The most relevant finding to biomarker studies was our demonstration that iron isotopes can be fractionated by chemical processes in the absence of biology. This was demonstrated using ion exchange chromatography. Our interpretation of the data is that fractionation occurs during equilibration between dissolved iron complexes in solution, which suggests that some of the natural variations in iron isotopic composition may be due to non-biological chemistry. This interpretation also provides insight into the mechanism(s) of biological iron isotope fractionation. This work was presented in 1999 at the V. M. Goldschmidt Conference, GSA and AGU, and published in Science in April, 2000.
We intend to follow up on these findings in Year 3 by conducting non-biological experiments using systems more relevant to nature than those used to date, and by exploring natural systems where biological influence is unlikely.
We also observed natural variations in the isotopic composition of Mo, which suggest a possible application for paleoredox studies. This will be a major area of emphasis in Year 3 in collaboration with the Harvard Team. Two manuscripts on Mo isotopes are in preparation.
PROJECT MEMBERS:Ariel Anbar
E. (Beth) Holman
RELATED OBJECTIVES:Objective 5.0
Describe the sequences of causes and effects associated with the development of Earth's early biosphere and the global environment.
Identify the environmental limits for life by examining biological adaptations to extremes in environmental conditions.
Search for evidence of ancient climates, extinct life and potential habitats for extant life on Mars.