How Does Life Begin and Develop?
Objective
1
Sources of 0rganics on Earth
Objective
2
Origin of Life's Cellular Components
Objective
4
Genomic Clues to Evolution
Objective
5
Linking Planetary and Biological Evolution
Does Life Exist Elsewhere in the Universe?
Objective
7
The Extremes of Life
Objective
8
Past and Present Life on Mars
Objective
9
Life's Precursors and Habitats in the Outer Solar System
Objective
10
Natural Migration of Life
Objective
11
Origin of Habitable Planets
Objective
12
Effects of Climate and Geology on Habitability
Objective
13
Extrasolar Biomarkers
What is Life's Future on Earth
and Beyond?
Objective
14
Ecosystem Response to Rapid Environmental Change
Objective
15
Earth's Future Habitability
Objective
16
Bringing Life with Us beyond Earth
Objective
17
Planetary Protection
Question: How Does Life Begin and Develop?
Linking Planetary and Biological Evolution
Objective 5: Describe the sequences of causes and effects associated with the development of Earth's early biosphere and the global environment.
It has already been established in specific instances that the environment has influenced the evolution of certain biota. For example, respiring animals have developed as atmospheric levels of oxygen increased. But the events that have triggered such linked trends and the forces that have sustained them are either unknown or poorly characterized. We can ask, did the geologically controlled availability of a particular trace element suddenly allow the synthesis of a key enzyme? Or, were biological developments themselves the initiators? To answer such questions, we must more accurately determine the times at which biological and geological events occurred, the sequences of the steps involved, and the budgets and distributions of geochemical reactants and products in the Earth's crust, oceans and atmosphere. In this way, we can attach dates and environmental contexts to evolutionary events, and thereby develop a robust, integrated history of the biosphere that incorporates biomolecular, paleoenvironmental, and paleobiological evidence.
Implementation
Near- to Mid-Term:
- Conduct intensive sampling
of ancient sediments to reconstruct, at high temporal resolution, their
settings at the times of their deposition.
- Examine such comprehensive
collections using geochemical and paleontological techniques at levels
of detail that allow the dissection of the record of key events in earth
history and the definition and testing of plausible relationships between
causes and effects.
- Elaborate the phylogenies
and mechanisms of evolution of key enzymes and of metabolic pathways
that had profound impacts on the environment (e. g., production of biomass,
oxygenic photosynthesis, sulfate reduction, nitrogen fixation, and methanogenesis).
- Define those features within
the record (morphological fossils or rock textures, biogeochemical signals)
that are related to those significant evolutionary transitions.
- Reconstruct the development
of the biogeochemical cycles of carbon and of its redox partners.
- Because of their clear relevance to planetary exploration, search specifically for strata that provide information about possible forms of life and chemical reactions in hydrothermal systems, aquifers, and evaporitic basins.
Future extensions:
- Determine the first appearances
of novel organisms and integrate them with molecular phylogenies using
quantitative approaches to the fossil record and precise geochronology.
A better understanding of the fossil records of extreme environments
will greatly improve the effectiveness of the search for life on other
worlds. These studies will lead to a better understanding of the evolution
of Earth's biosphere and environment.
- Develop chronologies on less than 10,000 year timescales to broaden our understanding of ecosystem responses to rapid changes, relevant to human-related timescales.