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: Does Life Exist Elsewhere in the Universe?
Extrasolar
Biomarkers
Objective 13: Define an array of astronomically detectable spectroscopic features that indicate habitable conditions and/or the presence of life on an extrasolar planet.
Perhaps within the next decade
or so, we will be able to obtain infrared spectra of extrasolar planets
that are situated within the habitable zones of stars within approximately
15 parsecs (approximately 50 light years) of our own Solar System. Accordingly,
we must develop the database for interpreting those spectra, both for
evidence of habitable conditions (e.g., the presence of liquid water)
and for evidence of life. Aspects of the strategy include developing appropriate
observational approaches that optimize sensitivity and spectral and spatial
resolution, creating models of atmospheric chemistry and its evolution,
and achieving an understanding of the factors that control the composition
of biological gas emissions to the atmosphere. We must develop the ability
to discriminate between those environmental conditions and gas compositions
that indicate a geologically active but "lifeless" planet, versus those
conditions and compositions that compel a biological interpretation.
Implementation
Near- to Mid-Term
- Determine the atmospheric compositions
that are maintained during the lifetimes of habitable planets that lack
biospheres.
- Define the biological and
environmental controls upon the emission of biogenic gases, including
oxygen, to the atmosphere.
- Develop global models for
the composition of Earth's early atmosphere, with particular emphasis
upon the fate of reduced biogenic gases. o Calculate synthetic spectra
of Earth-like planetary atmospheres, both with and without free O2,
to aid in designing future space-based interferometry missions, such
as TPF.
- Identify a menu of biologically-produced
volatile atmospheric species that could be detected using an interferometric
telescope having a resolving power (l/Dl) of 100.
- Define the spectral signatures of the earth's surface that might be detected remotely and provide evidence of life.
Future extensions:
- The requirements for detecting extrasolar biospheres in association with a range of atmospheric compositions will be key drivers behind the designs of interferometric telescopes that will obtain spectra of extrasolar planets. The astrobiology research program therefore must contribute substantially to the optimization of those designs. The program must lead the continuing search for novel methods to detect remote biospheres spectroscopically.