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Astronomical Observations of Terrestrial Planet Atmospheres
Project Investigators: David Crisp, Victoria Meadows, Jeremy Bailey
Other Project Members
Sarah Chamberlain (Doctoral Student)Summary
In this project we use telescopes and spectrometers on the Earth to study the atmospheres of Venus and Mars to learn more about the current conditions and history of water on these planets. This work also supports ongoing space-based observations of these worlds.
Astrobiology Roadmap Objectives:
- Objective 1.2: Indirect and direct astronomical observations of extrasolar habitable planets
- Objective 7.2: Biosignatures to be sought in nearby planetary systems
Project Progress
New spectroscopic observations of Venus were obtained with the IRIS2 imaging spectrograph on the 3.9m Anglo-Australian Telescope in two observing runs in 2007 June-July as part of an international coordinated program with the ESA Venus Express spacecraft. The observations are being analyzed in conjunction with earlier datasets from the same instrument in 2004 and 2005 and provide information on the composition, chemistry and circulation of the Venus atmosphere at a range of levels.
A particular focus has been to look at the water vapor content of the Venus lower atmosphere. Venus is extremely dry as compared with the Earth, but its high D/H ratio indicates that a substantial loss of water has occurred in the past. In-situ spacecraft measurements gave a wide range of values for the H2O mixing ratio. Remote sensing observations using the near-IR nightside windows have given a more consistent picture pointing to a constant H2O mixing ratio ~30 ppm below the clouds.
The IRIS2 observations in the near-IR windows and are being used to refine this value. In the course of this work we have found substantial discrepancies between different water vapor spectral line lists in the near-IR region. A comparison of eight H2O line lists has shown that all line lists used for previous Venus studies are incomplete in hot line and/or contain systematic errors in line intensities. We are currently assessing the impact of these effects on past water vapor measurements, and analyzing our new data using the most complete modern lists.
The Venus IRIS2 observations have also been used to obtain temperature maps for the Venus mesosphere at an altitude of ~95 km by looking at the rotational line intensities in the 1.27 μm O2 airglow band. The temperatures are typically 15-30 K higher than those expected from the standard Venus International Reference Atmosphere (VIRA). The observation of high temperatures at this altitude is consistent with the “warm layer” detected by the SPICAV instrument on Venus Express, and is believed to be the result of compressional heating of downwelling gas near the antisolar point.
Mission Involvement
ESA Venus ExpressOur ground-based observations were part of a coordinated program with Venus Express observations. David Crisp is a US participating scientist on the Venus Express mission. Jeremy Bailey is part of an ESA selected Supporting Investigator team.Field Expeditions
NameAAT Observations of VenusDates6-29-2007 - 7-4-2007Location31:16:37 South 149:03:58 EastDescriptionNear-infrared imaging spectroscopy observations of the Venus nightside were obtained covering the full disk of Venus, and a wavelength range from 1.1 to 2.4 m. The observations were part of a coordinated program with the ESA Venus Express spacecraft. The observations are being used to study aspects of the structure and composition of the Venus atmosphere from the surface to the upper mesosphere.NameAAT Observations of VenusDates7-20-2007 - 7-26-2007Location31:16:37 South 149:03:58 EastDescriptionNear-infrared imaging spectroscopy observations of the Venus nightside were obtained covering the full disk of Venus, and a wavelength range from 1.1 to 2.4 m. The observations were part of a coordinated program with the ESA Venus Express spacecraft. The observations are being used to study aspects of the structure and composition of the Venus atmosphere from the surface to the upper mesosphere.Cross-Team Collaborations
The project involved collaboration with the Australian Centre for Astrobiology (ACA). Jeremy Bailey and Sarah Chamberlain are members of the ACA, and carried out the observations and analysis of the AAAT IRIS2 data.
- Astronomical Observations of Terrestrial Planet Atmospheres
- Earth as an Extrasolar Planet
- Effects of stellar flares on atmospheres of habitable planets
- Hydrodynamic Escape from Planetary Atmospheres
- Modeling Early Earth Environments
- Planet Formation and Dynamical Modeling
- Planetary Habitability
- Planetary Surface and Interior Models and Super Earths
- Stromatolites in the Desert: Analogs to Other Worlds
- The Virtual Planetary Laboratory – The Life Modules - Photosynthesis
- VPL Climate and Radiative Transfer Models
- VPL Model Interfaces and the Community Tool
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