Research Fast Facts
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
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
The chemical model simulates atmospheric photochemistry and
thermochemistry, allowing the initial atmospheric composition to evolve
to equilibrium with the stellar radiation and atmospheric thermal
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
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
VPL scientists provide two-way communication between astrobiology and
NASA mission concepts in Earth, Solar System and extrasolar planetary