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  • The research of the NASA Astrobiology Institute's Virtual Planetary Laboratory (VPL) uses computer models of terrestrial planets to understand the nature and potential range of remote-sensing spectroscopic signs of planetary habitability and life which might be encountered by future planet detection and characterization missions.

  • The VPL is a suite of computer models for simulating the plausible range of atmospheric and surface compositions and climates for terrestrial planets. To do this, it combines radiative, climate, chemical, geological, exogenic and biological models.

  • The radiative transfer model employs a spectrum-resolving (line-by-line) multiple scattering algorithm to describe the spectrally dependent solar and thermal radiances and fluxes within and above realistic scattering, absorbing, emitting planetary atmospheres.

  • A simple, one-dimensional climate model combines the radiative fluxes and heating rates from the radiative transfer model with a vertical convective (mixing length) and conduction models to simulate the vertical thermal-equilibrium temperature profile of the surface-atmosphere system.

  • The chemical model simulates atmospheric photochemistry and thermochemistry, allowing the initial atmospheric composition to evolve to equilibrium with the stellar radiation and atmospheric thermal structure.

  • The geological model simulates outgassing and weathering processes that contribute to the atmospheric composition, and will incorporate both stagnant lid and plate tectonics, and reactive transport modeling for weathering.

  • The exogenic model simulates the effects of influx of extraterrestrial material (e.g. dust and meteor impacts) and atmospheric escape on the planet's environment.

  • Finally, the biological model simulates the impact of photosynthesis and respiration on the atmospheric composition, as well as the associated variations in the surface albedo spectrum, which can affect the solar radiative forcing and hydrological cycle at the surface. This theoretical research is supported by biological field work to understand spectral characteristics and gas fluxes for different forms of surface and aquatic life.

  • The objective of this project is to provide the fundamental research needed to support the remote-sensing detection of life, by improving our understanding of the use of spectra to discriminate between extrasolar planets with and without life.

  • This work is most directly relevant to the Astrobiology Roadmap Goals 1 and 7, on the nature of planetary habitability and the remote-sensing signs of life. However, work undertaken as part of the VPL planetary modeling effort also touches on aspects required to understand the Earth's early biosphere (Goal 4), biochemical adaptation to extreme environments (Goal 5), and environmental changes and the cycling of elements by ecosystems (Goal 6).

  • The work of the VPL provides valuable results to guide the design and search strategies for future NASA planet detection and characterization missions.

  • VPL scientists provide two-way communication between astrobiology and NASA mission concepts in Earth, Solar System and extrasolar planetary exploration.


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