2011 Annual Science Report

Massachusetts Institute of Technology Reporting  |  SEP 2010 – AUG 2011

Executive Summary

Our team’s primary focus this past year has been on evaluations of habitability. This work extends from the Earth’s past when complex life first appeared, to Mars and onwards to extrasolar planets.

Habitability of extrasolar planets
Using data from the Kepler mission and new ground-based detections, Lisa Kaltenegger and Dimitar Sasselov have identified potential and confirmed candidate planets that orbit within the Habitable Zone and could thus provide environments for basic and complex life to develop. They have also developed atmosphere models for extrasolar planetary environments for different geological cycles and varied environments that might permit the advent of complex life. The team modeled detectable spectral features that identify such planetary environments for future NASA missions like the James Webb Space Telescope.

Astrobiological Exploration of Mars
The Mars Science Laboratory (MSL) mission, due for launch on November 25th, 2011, has four primary science ... Continue reading.

Field Sites
28 Institutions
14 Project Reports
62 Publications
3 Field Sites

Project Reports

  • Molecular and Isotopic Investigations Across the Neoproterozoic

    We gathered new data on molecular and isotopic stratigraphic trends from Cryogenian and Ediacaran sequences from Canada, Oman and Mongolia. These continue to show that the biogeochemical carbon cycle was anomalous, and unlike any other period in Earth history, prior to the advent of complex animal life. While difficult to interpret in a robust way these data are reproducible, reflect real trends and are not the result of 'diagenetic alteration’ as some have proposed.

    ROADMAP OBJECTIVES: 4.2 5.2 6.1
  • Atmospheric Oxygen and Complex Life

    The biosynthesis of sterols requires oxygen but only in vanishingly low concentrations. Oxygen could be used by algae to make sterols in the surface ocean and, yet, at the same time, it would not be in sufficient concentration to destroy the mass-independent sulfur isotope signal for atmospheric oxygenation.

    Large sulfur isotope fractionations have been observed in sulfate reducing bacteria grown in a 'starvation’ regime, much as most natural populations experience. This casts doubt on the hypothesis that the large sulfur isotope fractionations seen in the Neoproterozoic rock record herald an increase in atmospheric oxygen and the inception of a new form of oxidative sulfur cycling.

    ROADMAP OBJECTIVES: 4.1 4.2 6.1
  • Proxies for Ocean Anoxia

    Episodes of widespread anoxia in past oceans are known as “Ocean Anoxic Events”. The ecosystem consequences of these events are actively debated. In this project, we are examining the chemical and isotopic signatures of the photosynthetic pigment, chlorophyll, to understand changes in ecosystems and the nutrients that fueled them. The seasonal oxygen minimum zone (OMZ) offshore Chile is being used as a modern analog.

    ROADMAP OBJECTIVES: 4.1 4.2 5.2 5.3 6.1
  • Astrobiological Exploration of Mars

    The Mars Science Laboratory (MSL) mission, due for launch in November 25th, 2011, has four primary science objectives for looking at habitable environments: assess the biological potential of at least one target environment by determining the nature and inventory of organic carbon compounds; characterize the geology of the landing region at all appropriate spatial scales by investigating the chemical, isotopic, and mineralogical composition of the surface and near-surface materials; investigate planetary processes of relevance to past habitability, including the role of water and carbon dioxide; and characterize the broad spectrum of surface radiation. Project scientist John Grotzinger and other MIT NAI team members have been contributing to numerous aspects of site selection, site evaluation and the optimal Mars environments for biosignature formation and preservation.

    ROADMAP OBJECTIVES: 1.1 2.1
  • Biomechanics of the Rangeomorph Fauna

    The oldest communities of fossil eukaryotes are found in the sedimentary rocks of Mistaken Point Newfoundland. These sediments were deposited in deep, slow-moving waters, at depths where light could not penetrate. Communities of fossil fronds preserved here reached up off the bottom, much like plants, but are thought to have lived by absorbing reduced compounds through their large surface area. In our work we show that growth off the seafloor provides an opportunity to reach higher flow velocity in this low flow environment. This exposure to flow breaks down diffusional limits, permitting more rapid uptake and growth. This opportunity is only available to larger-sized organisms, and this size advantage is exclusive to multicellular eucaryotes – not to competing bacteria with their smaller cell-size, and minimal multicellularity. Thus these communities and this advantage to multicellular form represents an important step in the evolution of complex multicellular life.

    ROADMAP OBJECTIVES: 4.2 5.2 6.1
  • Neoproterozoic Carbon Cycle

    The rock record late Neoproterozoic (540-800 Ma) appears to exhibit strong
    perturbations to Earth’s carbon cycle. This project seeks an understanding
    of the mechanisms that drive such events and their biogeochemical significance.

    ROADMAP OBJECTIVES: 3.2 4.2 5.1 5.2 6.1
  • Geochemical Signatures of Multicellular Life

    We continued our studies of the sterol complements of basal metazoa and their closest unicellular relatives and discerned what appears to be an evolutionary trend toward the universal use of cholesterol by higher animals. Inverse carbon isotope patterns of lipids and kerogen, that are a distinctive characteristic of organic matter found in Neoproterozoic sediments, record heterogeneous primary biomass comprising a dominant input from bacteria.

    ROADMAP OBJECTIVES: 3.2 4.2
  • Origins of Multicellularity

    By comparing animal genomes with genomes from their closest living relatives, the choanoflagellates, we can reconstruct the genome composition of the last common ancestor of animals.

    ROADMAP OBJECTIVES: 4.2
  • Protists of the Neoproterozoic

    T. Bosak (MIT), S. Pruss (Smith College), F. Macdonald (Harvard U.) and D. Lahr (U. Sao Paolo) discovered fossils of microscopic eukaryotes in limestone and dolostone strata deposited between the two Neoproterozoic low-latitude glaciations (between ~ 716 and 635 million years ago). These fossils include amoeba-like organisms that incorporated mineral-rich particles from the environment into their shells, mineral-rich shells of the oldest putative foraminiferans, and thick flask-shaped organic envelopes of the first putative ciliates, representatives of a major group of modern eukaryotes. These fossils demonstrate a previously unrecognized record of body fossils during the ~ 70 million years between the two “Snowball Earth” episodes and document the increasing diversity of morphologically and compositionally modern eukaryotes before the rise of complex animals.

    ROADMAP OBJECTIVES: 4.1 4.2 5.2 6.1
  • Timescales of Events in the Evolution and Maintenance of Complex Life

    For the first time, a precise and detailed chronology has been developed for numerous factors associated with the great mass extinction that ended to Paleozoic Era

    ROADMAP OBJECTIVES: 4.1 6.1
  • Evolution and Development of Sensory and Nervous Systems in the Basal Branches of the Animal Tree

    Animals interact with the world through complex sensory structures (eyes, ears, antennas, etc.), which are coordinated by collections of neurons. While the nervous and sensory systems of animals are incredibly diverse, a growing body of evidence suggests that many of these systems are controlled by similar sets of genes. We are looking at early branching and understudied lineages of the animal family tree (using the jellyfish Aurelia and the worm Neanthes respectively) to see if these animals use similar genes during neurosensory development as the better-studied fruit fly and mouse. This research is critical for determining which structures are shared between animals because of common ancestry (known as homologous structures) and those that evolved independently in different lineages. Ultimately, such research informs how morphologically and behaviorally complex animals evolve.

    ROADMAP OBJECTIVES: 4.1 4.2
  • Metabolic Networks From Single Cells to Ecosystems

    Members of the Segre’ group use systems biology approaches to study the complex network of metabolic reactions that allow microbial cells to survive and reproduce under varying environmental conditions. The resource allocation problem that underlies these fundamental processes changes dramatically when multiple cells can compete or cooperate with each other, for example through metabolic cross-feeding. Through mathematical models of microbial ecosystems and computer simulations of spatially structured cell populations, the Segre’ team aims at understanding the environmental conditions and evolutionary processes that favor the emergence of multicellular organization in living systems.

    ROADMAP OBJECTIVES: 4.1 4.2 5.1 5.2 6.1
  • Modelling Planetary Albedo & Biomarkers in Rocky Planets’/moons Spectra

    Using data from Kepler and new ground-based detections, Lisa Kaltenegger and Dimitar Sasselov have identified which confirmed and candidate planets orbit within the Habitable Zone and could provide environments for basic and complex life to develop. They have also developed atmosphere models for extrasolar planetary environments for different geological cycles and varied environments for the advent of complex life. The team modeled detectable spectral features that identify such planetary environments for future NASA missions like the James Webb Space Telescope.

    ROADMAP OBJECTIVES: 1.1 1.2 4.1 4.2 6.2 7.2
  • Paleontological Investigations of the Advent and Maintenance of Multicellular Life

    Understanding the origins and maintenance of complex life requires a two pronged approach: detailed investigations of the ecological and environmental context of the advent of complex life, as revealed by the fossil record, and exploration of the molecular underpinnings of how life becomes complex, how it is maintained, and how it is lost. The appearance of complex life that begins in the Ediacaran period around 580 million years ago and truly blossoms in the Cambrian Period about 530 million years ago reveals that ecological interactions – specifically predation – was a necessary component, and was depended upon the continuing oxygenation of the world’s oceans. Molecular investigations have revealed the genes and gene interactions that appear to be necessary for the advent of complex life, and what needs to be lost in order for complex life to become secondarily simplified. Together the fossil record and the molecular record indicate that evolving complex life involves both new genes and new ecologies within the context of permissive environmental circumstances.

    ROADMAP OBJECTIVES: 4.2