Estimates of visibility of the surface of Venus from descent probes and balloons

Moroz, V.I.

doi:10.1016/s0032-0633(01)00128-3

Cited by 41 publications

(38 citation statements)

References 13 publications

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“…Above and below the clouds are haze layers of mostly submicrometer particles. Hazes below the clouds have a total optical depth of less than 3 [ Ragent et al , 1985] that, however, might have been as high as 10 in Venera 8 near terminator measurements [ Moroz , 2002]. Ragent et al [1985], reviewing the different in situ measurements of hazes, gives no information for altitudes below 10 km.…”

Section: Background and Theorymentioning

confidence: 99%

Venus surface thermal emission at 1 μm in VIRTIS imaging observations: Evidence for variation of crust and mantle differentiation conditions

Müller¹,

Helbert²,

Hashimoto³

et al. 2008

J. Geophys. Res.

110

114

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[1] The Venus Express spacecraft images the nightside thermal emissions using the Visible and Infrared Thermal Imaging Spectrometer (VIRTIS). At 1.02, 1.10, and 1.18 mm, thermal emission from the surface is observed. The signal is attenuated by scattering and absorption in the dense atmosphere. The measured flux at the top of the atmosphere is positively correlated with surface temperature and surface emissivity. The surface temperature of Venus is relatively well constrained as being mainly a function of altitude with a gradient lesser or equal to the adiabatic lapse rate. This study examines the correlation of VIRTIS images showing a signal of the surface at 1.02 mm with viewing geometry, stray sunlight, cloud opacity, and topography and applies semiempirical relations to remove their influence. The remaining contrast can be either ascribed to surface emissivity or unexpected temperature variations. Temperature variations due to active volcanism are unlikely to be persistent over the time of observations; therefore, the mosaic of all processed images is here interpreted in terms of surface emissivity variation. The emissivity variation found is correlated with geomorphological features established from Magellan synthetic aperture radar images. It is generally lower at tessera terrain. Some, but not all, volcanic edifices show increased emissivity. Large lava flows in the Lada terra-Lavinia planitia region also show an increased thermal emission. This might indicate a more felsic surface composition of tessera highlands and large-scale extrusive volcanism of ultramafic composition. Motivation[2] The search for exoplanets yields an ever increasing number of known planets. With further improvements in observation techniques it will hopefully soon be possible to detect Earth sized planets orbiting their stars at distances where liquid surface water is stable. The special interest in planets with these attributes is of course motivated by the desire to find habitable planets or even life. Size and orbital distance comparable to Earth is by no means an ideal indicator of habitability as the Earth's neighboring planets demonstrate. Venus with eight tenths of Earth's mass and nearly three fourths of Earth's orbital distance is quite inhospitable. The surface of Venus is extremely hot owing to greenhouse climate imposed by its dense CO 2 atmosphere and sulfuric acid clouds. Surface and atmosphere are also dry compared to Earth [Taylor, 2006].[3] Comprehensive understanding of why Venus so utterly failed to become remotely habitable has not yet been achieved [Crisp et al., 2002]. One missing piece for the reconstruction of the evolution of Venus is global knowledge on the composition of the crust. The surface has been extensively mapped at radar wavelengths by the Magellan mission [Pettengill et al., 1991] which further revealed a unique geology [e.g., Saunders et al., 1991;Head et al., 1992;Solomon et al., 1992;Schaber et al., 1992;Phillips et al., 1992;Stofan et al., 1992Stofan et al., , 1997Hansen et al., 1997;Grimm...

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Section: Background and Theorymentioning

confidence: 99%

Venus surface thermal emission at 1 μm in VIRTIS imaging observations: Evidence for variation of crust and mantle differentiation conditions

Müller¹,

Helbert²,

Hashimoto³

et al. 2008

J. Geophys. Res.

110

114

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“…The SPICAV FOV above Maxwell Montes (distance to observed point $ 400 km) has a diameter of 14 km, while at low latitudes the FOV can exceed 100 km. Cloud scattering leads to blurring of surface features by a spatial extent of up to 80 km (Moroz, 2002;Bézard et al, 2009). We therefore used a boxcar average of 80 km for chosen spectral ranges at the maximal radiances of the windows where the obtained surface footprint was below 80 km and we use real SPICAV FOV if the spot was higher than 80 km.…”

Section: The Data Reductionmentioning

confidence: 99%

The CO2 continuum absorption in the 1.10- and 1.18-μm windows on Venus from Maxwell Montes transits by SPICAV IR onboard Venus express

Fedorova

Bézard

Bertaux

et al. 2015

Planetary and Space Science

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“…As it wells upward, this radiation gets mixed with thermal emissions of the atmosphere and is partially absorbed and multiply scattered by atmospheric gases Wavelength in pm and clouds. These processes also lead to a horizontal blurring of the information on the spatial origin of the surface properties imprinted in the IR radiance on a scale of 100 km 21 . Since surface signatures are far outweighed by scattered sunlight on the dayside, only nightside measurements can be used to derive surface data.…”

Section: Radiative Transfer Simulation Model and Single-spectrum Retrmentioning

confidence: 99%

VIRTIS on Venus Express: retrieval of real surface emissivity on global scales

et al. 2015

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The extraction of surface emissivity data provides the data base for surface composition analyses and enables to evaluate Venus' geology. The Visible and InfraRed Thermal Imaging Spectrometer (VIRTIS) aboard ESA's Venus Express mission measured, inter alia, the nightside thermal emission of Venus in the near infrared atmospheric windows between 1.0 and 1.2 µm. These data can be used to determine information about surface properties on global scales. This requires a sophisticated approach to understand and consider the effects and interferences of different atmospheric and surface parameters influencing the retrieved values. In the present work, results of a new technique for retrieval of the 1.0 -1.2 µm -surface emissivity are summarized. It includes a Multi-Window Retrieval Technique, a Multi-Spectrum Retrieval technique (MSR), and a detailed reliability analysis. The MWT bases on a detailed radiative transfer model making simultaneous use of information from different atmospheric windows of an individual spectrum. MSR regularizes the retrieval by incorporating available a priori mean values, standard deviations as well as spatial-temporal correlations of parameters to be retrieved. The capability of this method is shown for a selected surface target area. Implications for geologic investigations are discussed. Based on these results, the work draws conclusions for future Venus surface composition analyses on global scales using spectral remote sensing techniques. In that context, requirements for observational scenarios and instrumental performances are investigated, and recommendations are derived to optimize spectral measurements for Venus' surface studies.

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Estimates of visibility of the surface of Venus from descent probes and balloons

Cited by 41 publications

References 13 publications

Venus surface thermal emission at 1 μm in VIRTIS imaging observations: Evidence for variation of crust and mantle differentiation conditions

Venus surface thermal emission at 1 μm in VIRTIS imaging observations: Evidence for variation of crust and mantle differentiation conditions

The CO2 continuum absorption in the 1.10- and 1.18-μm windows on Venus from Maxwell Montes transits by SPICAV IR onboard Venus express

VIRTIS on Venus Express: retrieval of real surface emissivity on global scales

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