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?
Sources of Organics on Earth
Objective 1: Determine whether the atmosphere of the early Earth, hydrothermal systems or exogenous matter were significant sources of organic matter.
Determining the primary sources and nature of organic matter from which living systems emerged on the prebiotic Earth is still a controversial endeavor. The key proposed sources include synthesis in the atmosphere of the early Earth; synthesis in warm hydrothermal systems or in geothermal subsurface environments; delivery to the early Earth by comets, meteorites and microscopic, interplanetary dust particles; or some combination of these possibilities. Each hypothesis leads to different predictions about the composition and availability of organic starting material and the nature of the earliest pre-metabolic processes leading to the origin of life. We must, therefore, determine the relative contributions of each of these sources of organic material to life's origins on the primitive Earth, and define and characterize those mechanisms that allowed adequate concentrations of these chemicals for the necessary interactions and reactions to occur.
Implementation
Near to mid-term:
- Using space missions and infrared
telescopes, explore how organics, initially synthesized in the interstellar
dust cloud from which the Solar System was formed, are chemically altered
before they are delivered to earth. This research will help to determine
the chemical structure and composition of exogenous organic compounds
and the extent to which they contributed to the inventory of prebiotic
organics on earth. This task will benefit from missions to analyze organic
material in both interplanetary dust particles as well as meteor showers.
In addition, ground, air (SOFIA) and space-based (SIRTF) observatories
will provide key data.
- Conduct realistic laboratory
simulations of chemical reactions under the conditions existing on planetary
bodies, on the surface of the primitive earth and in hydrothermal vents.
Investigate the potential of the synthesized compounds to contribute
to the formation of biological structures.
- Perform computer modeling of
prebiotic chemical synthesis in different environments taking into account
appropriate external constraints, such as energetics, temperature, pressure,
and surface catalysis potential.
- Examine the geological record
for evidence of environmental conditions on the early earth. Examine
ancient rock formations for the signature of early life in the form
of microfossils, isotope ratios and mineral assemblages, and obtain
evidence for the redox state of the earth mantle near the time of the
origin of life. A reducing mantle was essential to maintain a reducing
atmosphere on the prebiotic earth.
- Study natural environments (e.g., hydrothermal vents) as models for primordial chemistry.
Future extensions:
- Perform space missions to characterize
more precisely quantities and compositions of exogenous and sub-surface
organic material.
- Construct integrated models
of the chemistry on the prebiotic earth that include contributions from
different sources of organic matter and environmental constraints.
- Perform planetary subsurface
missions to obtain virgin endogenous material.
- Perform planetary missions to understand possibilities for prebiotic evolution.