4 items with the tag “carbon cycle

  • Molecular Biosignatures: Hopanoid Sources in Modern Systems
    NAI 2013 Massachusetts Institute of Technology Annual Report

    Molecular fossils preserved in sedimentary rocks provide a record of Earth’s early biosphere and its associated carbon cycle. Among the earliest and most abundant molecular fossils are the hopanoids. Derived primarily from bacteria, their diagenetic products, the hopanes, are detectable over timescales of billions of years and have been proposed to be among the most abundantly preserved molecules on Earth. However, an overall picture of their environmental, physiological, and taxonomic origins remains elusive. Are they primarily remnants of primary producers or of heterotrophic consumers? Do they primarily come from free-living marine communities, or from shallow mats, tidal zone communities, or even terrigenous runoff? Here we aim to obtain compound-specific carbon isotope data for hopanoids to infer their sources in modern systems, as proxies for understanding ancient environments.

    ROADMAP OBJECTIVES: 3.2 5.1 5.3 6.1
  • Molecular Biosignatures: Reconstructing Events by Comparative Genomics
    NAI 2013 Massachusetts Institute of Technology Annual Report

    Reconstructing ancient events in genome evolution provides a valuable narrative for planetary history. Phylogenetic analysis of protein families within microbial lineages can be used to detect horizontal gene transfers and the evolution of new metabolic pathways and physiologies, many of which are significant in reconstructing ancient ecologies and biogeochemical events. These gene transfers can also be used to constrain molecular clock models for early life evolution, applying principles of stratigraphy and date calibration. A better understanding of gene evolution, including partial horizontal gene transfer, is needed to improve these inferences and avoid systematic errors.

    ROADMAP OBJECTIVES: 3.2 3.4 4.1 4.2 4.3 5.1 5.2 6.1
  • Neoproterozoic Aerobic Transition
    NAI 2013 Massachusetts Institute of Technology Annual Report

    The Proterozoic carbon isotopic record contains evidence of a series of large perturbations to the global carbon cycle, some or all of which may be associated with changes in atmospheric O2. Our team is formulating a theoretical model to explain not only these disruptions but also the permanent increase in O2 levels that occurred by the end of the Proterozoic.

    ROADMAP OBJECTIVES: 1.1 4.1 4.2 5.2 6.1
  • Planetary Surface and Interior Models and SuperEarths
    NAI 2013 VPL at University of Washington Annual Report

    We use computer models to simulate the evolution of the interior and the surface of real and hypothetical planets around other stars. Our goal is to work out what sorts of initial characteristics are most likely to contribute to making a planet habitable in the long run. Observations in our own Solar System show us that water and other essential materials are continuously consumed via weathering (and other processes: e.g., subduction, sediment burial) and must be replenished from the planet’s interior via volcanic activity to maintain a biosphere. The surface models we are developing will be used to predict how gases and other materials will be trapped through weathering and biological processes over time. Our interior models are designed to predict tidal effects, heat flow, and how much and what sort of materials will come to a planet’s surface through resurfacing and volcanic activity throughout its history.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 5.2 6.1