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Objectives

How Does Life Begin and Develop?

Objective 1
Sources of 0rganics on Earth

Objective 2
Origin of Life's Cellular Components

Objective 3
Models for Life

Objective 4
Genomic Clues to Evolution

Objective 5
Linking Planetary and Biological Evolution

Objective 6
Microbial Ecology

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?
Effects of Climate and Geology on Habitability

Objective 12: Define climatological and geological effects upon the limits of habitable zones around the Sun and other stars to help define the frequency of habitable planets in the universe.

 

The limits of a star system's habitable zone are determined in part by the stability of liquid water on the surface of planetary bodies, both instantaneously and over long time periods, as the parent star luminosity changes. Planetary habitability also depends on the stability of the planetary system, including the gravitational effects of large (Jovian-sized) planets or nearby stars on the distribution and dynamics of potential large impactors. Detection of habitable planets outside of our own Solar System will rely on spectroscopic observation of key atmospheric constituents--including water, carbon dioxide, ozone, and possibly others. Among the factors which affect liquid water's stability are the mass, composition, and dynamics (including effects of clouds) of a planet's atmosphere. The development of multidimensional general atmospheric circulation models--including the effects of clouds--for other planets will be critical in defining the distribution of liquid water in the universe.

Implementation

Near to mid-term:

  • Conduct a theoretical research program to model the role of clouds (both CO2 and H2O) on early Mars, to explore cloud formation, radiative effects, and effects on atmospheric dynamics, all of which affect the location of the outer edge of the liquid water region, or habitable zone.

  • Study the radiative effect of water clouds in a dense, runaway greenhouse atmosphere such as may have existed on Venus, and determine how this influences the location of the inner edge of the habitable zone.

  • Extend these models to include a broader range of planetary sizes and orbital radii, in order to explore more fully the role of climate in determining the extent of habitable zones in other putative solar systems.

  • Search for direct, in situ evidence for liquid water on Mars, along with other surface minerals (e.g., carbonates and sulfates) that may provide information about long-term climate evolution.

  • Develop better models of how hydrogen escapes from H2-rich, primitive atmospheres and how this would have affected atmospheric evolution on the early earth and on other, Earth-like planets.

  • Determine whether the primitive Earth (and, by extension, other planets) could have developed an organic-rich, atmospheric haze layer such as that found on Titan, and explore the consequences of such haze layers for atmospheric and biological evolution.

Future Extensions:

  • These models ultimately will generate a paradigm for planetary habitability to help guide, as well as be tested by, astronomical observations of extrasolar habitable planets. The interplay between these climate models and the Mars sample return analysis program will allow us to determine whether Mars is inhabited now or whether it may have been inhabited in the past.
         


Questions? Comments?

Responsible NASA Official:
Mary Voytek

Last Updated: October 27, 2014