Iron Isotope Biosignatures

• DOI: 10.1126/science.285.5435.1889
• Publication Date: 2002-07-27T09:37:20Z
• Authors: Brian L. Beard; Clark M. Johnson; Lea Cox; Henry Sun; Kenneth H. Nealson; Carmen Aguilar
• Keywords: Ferrihydrite

The 56 Fe/ 54 Fe of Fe-bearing phases precipitated in sedimentary environments varies by 2.5 per mil (δ values +0.9 to −1.6 mil). In contrast, the igneous rocks from Earth and moon does not vary measurably = 0.0 ± 0.3 Experiments with dissimilatory Fe-reducing bacteria genus Shewanella algae grown on a ferrihydrite substrate indicate that δ ferrous solution is isotopically lighter than 1.3 mil. Therefore, range may reflect biogenic fractionation, isotopic composition be used trace distribution microorganisms modern ancient Earth.