NASA Astrobiology Institute (NAI)

1. Sulfur and Phosphorus Cosmochemistry: Implications

   Project Investigators:

   Other Project Members

   Kristin Block (Masters Student)

   David Bryant (Collaborator)

   Jason Dworkin (Collaborator)

   H. G. Edwards (Collaborator)

   Terence Kee (Collaborator)

   Dante Lauretta (Collaborator)

   H. Melosh (Collaborator)

   Olivier Mousis (Collaborator)

   Alex Pavlov (Collaborator)

   Summary

   We are working to understand the evolution and development of phosphorus and sulfur biomolecules in modern life. These elements are both highly important in several biologic processes. Understanding how these elements reacted on the early earth will help us understand the origin of life. We have discovered several promising chemical routes to the formation of critical biomolecules, and suggest that these processes were due to unique conditions present in the earth's early history, including lightning and meteorite impacts.

   Astrobiology Roadmap Objectives:

   • Objective 3.1: Sources of prebiotic materials and catalysts
   • Objective 3.2: Origins and evolution of functional biomolecules
   • Objective 3.3: Origins of energy transduction
   • Objective 3.4: Origins of cellularity and protobiological systems
   • Objective 4.1: Earth's early biosphere
   • Objective 4.3: Effects of extraterrestrial events upon the biosphere
   • Objective 5.1: Environment-dependent, molecular evolution in microorganisms
   • Objective 7.1: Biosignatures to be sought in Solar System materials

   Project Progress

   We have solved one of the major problems in the origins of life- the development of condensed phosphates through simple geologic processes (Pasek et al., 2008, Angewandte Chemie International Edition). This work highlights how the oxidation of reduced P compounds leads to polyphosphates, the most simple and robust synthesis yet of these critical P compounds.

   Additionally, we have discovered the first terrestrial occurrence of reduced P compounds in natural samples. These phases are found in fulgurites, melts formed by lightning strikes (Figure 1), and highlight the relevance of phosphate reduction to geochemical environments.

   
   

   First identification of a reduced P species in a terrestrial sample. Scale bar 20 m. Image is a back-scattered electron map of a small grain near the center of a fulgurite. Light material is a CaHPO3 compound of unknown structure. It intermingles with CaCO3, and the dark grain at the bottom is a quartz grain.

   
   Fig 1. First identification of a reduced P species in a terrestrial sample. Scale bar 20 ?m. Image is a back-scattered electron map of a small grain near the center of a fulgurite. Light material is a CaHPO3 compound of unknown structure. It intermingles with CaCO3, and the dark grain at the bottom is a quartz grain.

   Cross-Team Collaborations

   Work with Jason Dworkin (NASA GSFC) on determining organic survivability during high energy events (in progress)
   Work with Roger Buick and Jelte Hartemeijer (U Washington) on determining phosphorus chemistry of ancient geologic sediments (in progress)
   Work with George Cody and Andrew Steele (CIW) on analyzing compounds in fulgurites (in progress)

Publications

Bryant, D.E.  (2008).  Electrochemical studies of iron meteorites.  Phosphorus redox chemistry on the early Earth.  International Journal of Astrobiology, Submitted.

Carter, E.A.  (2008).  Raman Spectroscopy and Scanning Electron Microscopy of a Fulgurite.  Journal of Geophysical Research, Submitted.

Mousis, O.  (2008).  Partical volatilization of the planetesimals that formed Titan.  Astrophysical Journal, In Press.

Pasek, M.A.  (2008).  Extraterrestrial flux of potentially prebiotic C, N, and P to the early Earth.  Origins of Lie and Evolution of Biospheres, 38(1):5-12.t.

Pasek, M.A.  (2008).  Lightning Reduction of Phosphate: Implications for Phosphorus Biogeochemistry.  Geochimica et Cosmochimica Acta, Submitted.

Pasek, M.A.  (2008).  Prebiotic condensed phosphates from oxidation of reduced phosphorus.  Angewandte Chemie International Edition, In Press.

Pasek, M.A.  (2008).  Rethinking early Earth phosphorus geochemistry.  Proceedings of the National Academy of Sciences USA, 105(3):853-858.