Journal ArticleDOI
The upper atmosphere of Venus during morning conditions
U. von Zahn,K. H. Fricke,Donald M. Hunten,Dieter Krankowsky,Konrad Mauersberger,Alfred O. Nier +5 more
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The structure and composition of the Venus upper atmosphere between 130 and 650 km altitude were measured for a solar zenith angle of approximately 60 deg by the neutral gas mass spectrometer on board the Pioneer Venus multiprobe bus.Abstract:
The structure and composition of the Venus upper atmosphere between 130- and 650-km altitude were measured for a solar zenith angle of approximately 60 deg by the neutral gas mass spectrometer on board the Pioneer Venus multiprobe bus. Below 180 km a wavelike structure is quite evident in the CO2 and He number density profiles. For altitudes above 100 km a one-dimensional model of the Venus upper atmosphere during morningside conditions (MS model) is presented. Number densities at 150-km altitude are as follows: CO2 equals 4.2 x 10 to the 9th, N2 equals 1.1 x 10 to the 9th, CO equals 2.8 x 10 to the 9th, and He equals 4.8 x 10 to the 6th per cu cm. The homopause altitudes for N2 and He are at 136 and 130 km, respectively.read more
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Turbulence and stress owing to gravity wave and tidal breakdown
TL;DR: In this article, the effects of mean winds and gravity waves on the mean momentum budget were investigated and it was shown that the existence of critical levels in the mesosphere significantly limits the ability of gravity waves to generate turbulence.
Journal ArticleDOI
M stars as targets for terrestrial exoplanet searches and biosignature detection.
John Scalo,Lisa Kaltenegger,Antígona Segura,Malcolm Fridlund,Ignasi Ribas,Yu. N. Kulikov,John Lee Grenfell,Heike Rauer,P. Odert,Martin Leitzinger,Franck Selsis,Maxim L. Khodachenko,Carlos Eiroa,James F. Kasting,Helmut Lammer +14 more
TL;DR: It is concluded that attempts at remote sensing of biosignatures and nonbiological markers from M star planets are important, not as tests of any quantitative theories or rational arguments, but instead because they offer an inspection of the residues from a Gyr-long biochemistry experiment in the presence of extreme environmental fluctuations.
Journal ArticleDOI
Coronal mass ejection (CME) activity of low mass M stars as an important factor for the habitability of terrestrial exoplanets. II. CME-induced ion pick up of Earth-like exoplanets in close-in habitable zones.
Helmut Lammer,Herbert Lichtenegger,Yuri N. Kulikov,J.-M. Grießmeier,Naoki Terada,Nikolai V. Erkaev,Helfried K. Biernat,Helfried K. Biernat,Maxim L. Khodachenko,Ignasi Ribas,Thomas Penz,Thomas Penz,Franck Selsis +12 more
TL;DR: It is suggested that larger and more massive terrestrial-type exoplanets may better protect their atmospheres against CMEs, because the larger cores of such exoplanet would generate stronger magnetic moments and their higher gravitational acceleration would constrain the expansion of their thermosphere-exosphere regions and reduce atmospheric escape.
Journal ArticleDOI
Measurements of thermal structure and thermal contrasts in the atmosphere of Venus and related dynamical observations: Results From the four Pioneer Venus Probes
Alvin Seiff,Donn B. Kirk,Richard E. Young,Robert C. Blanchard,John T. Findlay,G. M. Kelly,Simon C. Sommer +6 more
TL;DR: The thermal structure of the Venus atmosphere and differences in structure with latitude (up to 60 deg) and clock hour (from midnight to 8 AM) have been measured in situ from a height of 126 km to the surface by instruments on the four Pioneer Venus entry probes as discussed by the authors.
Journal ArticleDOI
Comparative terrestrial planet thermospheres: 3. Solar cycle variation of global structure and winds at solstices
TL;DR: In this paper, a comparison of the combined seasonal-solar cycle responses of the thermospheres of Earth and Mars using the National Center for Atmospheric Research (NCAR) Thermospheric General Circulation Model (TGCM) utility to address the coupled energetics, dynamics, and neutral-ion composition above ∼100 km.
References
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Journal ArticleDOI
A global thermospheric model based on mass spectrometer and incoherent scatter data MSIS, 1. N2 density and temperature
A. E. Hedin,Joseph E. Salah,J. V. Evans,Carl A. Reber,G. P. Newton,Nelson W. Spencer,D. C. Kayser,D. Alcaydé,P. Bauer,L. L. Cogger,J. P. McClure +10 more
TL;DR: In this article, mass spectrometers on five satellites (AE-B, Ogo 6, San Marco 3, Aeros A, and AE-C) and neutral temperatures inferred from incoherent scatter measurements at four ground stations are combined to produce a model of thermospheric neutral temperatures and nitrogen densities similar to the Ogo6 empirical model (Hedin et al., 1974).
Journal ArticleDOI
Composition and structure of Mars' Upper atmosphere: Results from the neutral mass spectrometers on Viking 1 and 2
TL;DR: In this paper, the upper atmospheric mass spectrometers of the Viking 1 and 2 were used to study the composition and structure of Mars' upper atmosphere at all heights below 180 km and the isotopic composition of carbon and oxygen in the Martian atmosphere is similar to that in the terrestrial atmosphere.
Journal ArticleDOI
Measurements of thermal structure and thermal contrasts in the atmosphere of Venus and related dynamical observations: Results From the four Pioneer Venus Probes
Alvin Seiff,Donn B. Kirk,Richard E. Young,Robert C. Blanchard,John T. Findlay,G. M. Kelly,Simon C. Sommer +6 more
TL;DR: The thermal structure of the Venus atmosphere and differences in structure with latitude (up to 60 deg) and clock hour (from midnight to 8 AM) have been measured in situ from a height of 126 km to the surface by instruments on the four Pioneer Venus entry probes as discussed by the authors.
Journal ArticleDOI
Structure and meteorology of the middle atmosphere of Venus: Infrared remote sensing from the Pioneer Orbiter
Fredric W. Taylor,Reinhard Beer,M. T. Chahine,David J. Diner,L. S. Elson,R. D. Haskins,Daniel J. McCleese,John V. Martonchik,P. E. Reichley,S. P. Bradley,J. Delderfield,John T. Schofield,Crofton B. Farmer,Lucien Froidevaux,J. Leung,M. T. Coffey,John C. Gille +16 more
TL;DR: The results of the Pioneer Venus orbiter radiometric temperature-sounding experiment are presented with examples of each of the primary data products as discussed by the authors, where the measured temperature field is used to model the dynamics of the middle atmosphere from 60 to 140 km, and the thermal and solar fluxes are used to calculate the planetary radiation budget.
Journal ArticleDOI
Mass spectrometric measurements of the neutral gas composition of the thermosphere and exosphere of Venus
TL;DR: The neutral gas composition and density in the thermosphere of Venus is measured with a quadrupole mass spectrometer on the Pioneer Venus orbiter as discussed by the authors, where data are obtained near periapsis once per day approximately 150-250 km above the surface.