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Venus Express searching for life – on Earth
10 October 2008
| | This image composite shows the signatures of methane (CH4), carbon dioxide (CO2), ozone (O3) and nitrous oxide (N2O), minor species of the Earth’s atmosphere but powerful greenhouse gases, detected by the Visual and Infrared Thermal Imaging Spectrometer (VIRTIS) on board ESA’s Venus Express at infrared wavelengths, while the spacecraft was pointing Earth along its orbit around Venus. Our planet was just a pixel in VIRTIS’s field of view.
The spectral signatures of these molecules, or chemical fingerprints, are shown for two observing sessions and are plotted by the two curves displayed in two different colours. During the observations Earth was showing to Venus Express the ‘face’ simulated in the image at the top. The light detected by VIRTIS is the thermal emission from the Earth’s surface and, partially, the atmosphere.
These observations are relevant as they proof that a distant planet such as an extra-solar planet can reveal to an instrument like VIRTIS the signatures of chemical compounds composing the atmosphere and surface.
VIRTIS obtained these spectra on 5 and 6 August 2007. During these observations, Venus Express’s distance from Earth was about 78 million km, while the spacecraft’s distance from Venus was about 14 500 km.
Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA (Earth views: Solar System Simulator JPL-NASA) | |  |  | |
| | | | | | This image composite shows the signatures of water (H2O) and oxygen (O2) detected by the Visual and Infrared Thermal Imaging Spectrometer (VIRTIS) on board ESA’s Venus Express at visible and near-infrared wavelengths, while the spacecraft was pointing Earth along its orbit around Venus. Our planet was just a pixel in VIRTIS’s field of view.
The spectral signatures of these molecules, or chemical fingerprints, are shown for several observing sessions and are plotted by curves displayed in different colours. Each curve correspond to the Earth showing a different face to Venus Express (see the simulated Earth images at the top), and at different distances. The light detected by VIRTIS was mainly reflected by clouds.
These observations are relevant as they proof that a distant planet such as an extra-solar planet can reveal to an instrument like VIRTIS the signatures of chemical compounds that may be preliminary signs of a possible planet’s habitability. Within this wavelength range, molecules such as chlorophyll can also be detected.
In addition, repeated spectral observations, and the fact that the results vary, can provide fundamental clues about the presence of a weather system on the planet (such as clouds moving in the sky), of glaciers and oceans located on different regions, and also give information about the rotation of the planet around its parent star.
VIRTIS obtained these spectra between April and August 2007. During the period of observations, Venus Express’s distance from Earth ranged between about 62 and 175 million km, while the spacecraft’s distance from Venus ranged between 1000 and 20 000 km.
Credits: ESA/VIRTIS/INAF-IASF/Obs. de Paris-LESIA (Earth views: Solar System Simulator JPL-NASA) | | | | |
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