Venus Atmospheric Composition in situ Data: A Compilation

Abstract

The Venus atmosphere is of significant interest yet only rudimentary solid data has been gathered about its composition and chemistry. These measurements are scattered through time and place and are limited by parameters such as resolution and error margins as well as reinterpretations. This paper presents an extensive compilation of published in situ data for the atmospheric composition of Venus. It also includes remotely gathered measurements and some extrapolated and modeled data for the lower atmosphere. The composition tables are divided in four categories: noble gases, reactive gases, noble and non-noble isotopes. These tables were first presented in 2016 within the scientific heritage appendix of the Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission proposal. These tables provide respective measurements, error margins, techniques, altitudes, instruments, mission and references. The objective of this paper is to provide a simple, comprehensive list of available measurements to date; in particular, the in situ data, to serve as a quick overall Venus atmosphere data reference.

Key point / Plain language summary:

A compilation of in situ Venus atmospheric data from a variety of journals and difficult to locate sources.

1. Introduction

Venus is our nearest planetary neighbor, excluding the Moon, yet we only have rudimentary knowledge of its deep atmosphere and geology. This is not for the lack of trying. Several spacecraft have been sent to Venus, either as orbiters, atmospheric probes, or landers, with differing levels of success. There have been opportunistic observations of Venus using instruments on spacecraft ‘flybys’ that were headed elsewhere as well as numerous Venus observations conducted from Earth-based telescopes or made with the naked-eye. The motivation for this paper was to create an easily accessible manuscript that contains the sum total of all previous measured and modeled Venus composition data that could be used as a straightforward reference. Specifically, the renewed interest in sending spacecraft to Venus, as demonstrated by the recent NASA Discovery and New Frontiers Mission opportunities, justified such a compilation. In the early stages, it appeared that this task would be both simple and quick but it became quickly evident that without proper guidelines, this effort would devolve into a multifaceted morass. Therefore, we compiled an extensive list of published in situ measurements of the Venus atmosphere with some additional data derived from modeling.

The Venus environment is characterized by extreme conditions from the global sulfuric acid clouds to the high temperatures and pressures present at the surface (740 K and 95.6 bar). This challenging environment resulted in relatively few in situ measurements and remote observations are for the most part, limited to the region above the clouds. This dearth of hard data restricts what can be ascertained directly and requires the use of models in order to predict complex composition and processes within the Venus atmosphere. As a result, it is not uncommon for some extrapolated/modeled data to be quoted as ‘fact’, particularly for the deep atmosphere (below the clouds to the surface). There exist a large variety of Venus data compilations and presentations but an inescapable fact is that the in situ compositional data of the deep atmosphere, originates from the Venera, VeGa and Pioneer Venus missions. The last of these missions, VeGa 2, completed its task in June 1985. It should be noted that none of the entry/descending probes of the Venera or Pioneer missions were able to collect composition data until the probes became sub-sonic which typically occurred below 64km in almost all of the cases. More recent data was obtained through remote Earth-based, fly-by or orbiter observations. Tables 1a and 1b lists the spacecraft and Earth/space-based facilities that have gathered data about Venus and whose data is reflected in this compilation.

Table 1a:

Missions to Venus and Spacecraft that returned Venus data

Date Launched	Name (Nation)a	Type	Venus Dateb (Lat, Long)	Comments
27 Aug 1962	Mariner 2 (USA)	Flyby	14 Dec 1962 (n/a)	First successful Venus flyby
12 Jun 1967	Venera 4 (USSR)	Probe	18 Oct 1967 (unknown)	First spacecraft to transmit data from a planet’s atmosphere
14 Jun 1967	Mariner 5 (USA)	Flyby	19 Oct 1967 (n/a)
5 Jan 1969	Venera 5 (USSR)	Probe	16 May 1969 (3°S, 18°)
10 Jan 1969	Venera 6 (USSR)	Probe	17 May 1969 (5°S, 23°)
17 Aug 1970	Venera 7 (USSR)	Lander	15 Dec 1970 (5°S, 351°)	First transmissions from the surface of another planet
27 Mar 1972	Venera 8 (USSR)	Lander	22 Jul 1972 (10°S, 335°)
3 Nov 1973	Mariner 10 (USA)	Flyby	5 Feb 1974 (n/a)
8 Jun 1975	Venera 9 (USSR)	Orbiter/Lander	22 Oct 1975 (32°N, 291°)	First image of Venus surface
14 Jun 1975	Venera 10 (USSR)	Orbiter/Lander	25 Oct 1975 (16°N, 291°)	Transmitted 65min from surface; Surface images
20 May 1978	Pioneer Venus 1 (USA)	Orbiter	4 Dec 1978 (n/a)	Radar map 73°N/63°S @ 75km resolution; in operation for ~14yrs
8 Aug 1978	Pioneer Venus 2 (USA)	Multiprobe 1 large 3 small	9 Dec 1978 (4.4°N, 304°; Large Probe)	Small probes: North (59.3°N,4.8°); Day (31.3°S,317°); Night (28.7°S,56.7°) Two of three survived impact
9 Sep 1978	Venera 11 (USSR)	Flyby/Lander	25 Dec 1978 (14°S, 299°)	Date reflects surface landing
14 Sep 1978	Venera 12 (USSR)	Flyby/Lander	21 Dec 1978 (7°S, 294°)	Lander relayed data for 110 minutes after reaching the surface.
30 Oct 1981	Venera 13 (USSR)	Flyby/Lander	1 Mar 1982 (7.5°S, 305°)	First color images of Venus surface; relayed data for 127 mins
4 Nov 1981	Venera 14 (USSR)	Flyby/Lander	5 Mar 1982 (13.25°S, 310°)	Lander relayed data for 57 minutes after reaching the surface.
2 Jun 1983	Venera 15 (USSR)	Orbiter	10 Oct 1983 (n/a)	Mapping
7 Jun 1983	Venera 16 (USSR)	Orbiter	14 Oct 1983 (n/a)	Mapping
15 Dec 1984	VeGa 1 (USSR)	Flyby/Probe/Lander	11 Jun 1985 (7.2°N, 177.8°)	Balloon-gondola gathered atmos data (survived 46.5 hrs); lander relayed data for 56 mins
21 Dec 1984	VeGa 2 (USSR)	Flyby/Probe/Lander	15 Jun 1985 (6.45°S, 181.08°)	Balloon-gondola gathered atmos data (survived 46.5 hrs); lander relayed data for 57 mins
4 May 1989	Magellan (USA)	Orbiter	10 Aug 1990 (n/a)	Radar mapping; 98% coverage; remained in orbit ~4 yrs
4 Aug 2004	MESSENGER (USA)	Flyby	24 Oct 2006 5 Jun 2007 (n/a)	Destination: Mercury Remote measurements/images of Venus atmosphere
9 Nov 2005	Venus Express (Europe)	Orbiter	7 May 2006 (n/a)	Global mapping; remote analyses; plasma, cloud, atmos studies; final mission duration ~9 yrs
20 May 2010	Akatsuki (Japan)	Orbiter	7 Dec 2015 (n/a)	Failed initial orbit 2010 insertion; atmos dynamics & cloud physics; ongoing

^aMission design and operation: NASA(USA), Lavochkin(USSR), ESA(Europe), JAXA(Japan)

^bDate of flyby/entry/landing of spacecraft; if known, Venus latitude and longitude of final resting spot.

Table 1b:

Earth- and Space-based facilities referenced in this study for Venus data

Facility/Spacecraft	Instrument	Comments
Apache Point Observatory	3.5 m Telescope	TripleSpec spectrograph
Extreme Ultraviolet Explorer (EUVE)	Wolter-Schwarzschild Type II grazing incidence mirror	Launch: June 1992 Deactivated: Jan 2001
Mauna Kea Observatories	Canada-France-Hawaii 3.6m Telescope	Fourier Transform Spectrometer
International Ultraviolet Explorer (IUE)	Long Wavelength Primary Camera: High Dispersion Mode/Small Aperture	Launch: Jan 1978 Decommission:Sept 1996
NRAO Very Large Array	Radio observations	Microwave frequencies
Observatoire de Haute Provence, France	1.9 m Telescope	Michelson Interferometer

1.1. Overview of Previous Venus Atmospheric Data Compilation Studies

The Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging (DAVINCI) mission proposal included a science heritage table within its appendix on the atmospheric composition of Venus. While conducting background research for this mission, it was evident that there needed to be one comprehensive, clear-cut table of the existing measured Venus atmospheric data. Limaye et al. (2018) present a comprehensive review of Venus thermal structure and radiative balance results but not the composition. Some previous compilations, although unquestionably excellent such as the Venus International Reference Atmosphere, aka VIRA, (Kliore et al. 1985), are now outdated while others were unclear or did not explain how values were derived. Imagine the frustration when significant literature digging was required to determine whether a value was an extrapolation, or has been accepted as ‘fact’ because the original source receded far into citation history, or had been derived solely from models or from well-studied estimates. This additional research was, unsurprisingly, neither straightforward nor swift due to difficulty in obtaining original sources, if cited at all. It was also easy to fall into a false sense of knowledge regarding the breadth of data because, at first, the data appear comprehensive but upon closer inspection, the data is limited in scope either by vertical resolution, massive error bars, or having no measurements whatsoever, i.e., oxygen at depth. This paper includes the aforementioned Venus data compilation from the DAVINCI proposal and recently obtained remote data. It is hoped that this presentation of the current knowledge of Venus’ atmospheric composition data will save future investigators the frustration and effort of tracking down the proverbial needles in a haystack. The intent is to not to debate whether a measurement or estimate was made correctly or not; rather it is to report in one place currently known and published measurements regarding the Venus atmosphere.

2. Methodology

2.1. Measurement Discussion

The data in these tables list measured values and a concerted effort was made to only include data from original sources. Modeled data were mostly avoided, unless well justified, in order to maintain the basic original data integrity of the tables. As such, the values presented in this paper are taken verbatim from the sources using original units and connotations unless noted otherwise. Later papers that quote the same value from an earlier source are not included. Some values that were tweaked over the years are also included if the reworked values have clear explanations and techniques. In order to ease access and understanding, the tables include a comment column for each item to provide information that is not reflected is the main body of the table. For example, a statement about how the data value was derived or settled upon would be noted from the original source. Theoretical or modelled data are indicated.

While compiling this data and speaking with researchers in the community, it became apparent that is not always obvious how the measurements are reported. The terms abundance and ‘mole fraction’ have been used interchangeably which, at times, has led to confusion as to what exactly the measurements represent. As this situation appears to occur fairly often, it seemed to be a useful exercise to clarify the measurement definition with a brief overview. When we refer to one of the first major and commonly cited compendiums of measured data, von Zahn et al. (1983), the reported measurements for each species are provided as mixing ratios: “We provide … mixing ratios x_i = n_i/Σ n_i, (with n_i being the number density of species i) of all those gases which have been positively identified in Venus’s atmosphere below 100 km.” The number density is a fixed number of particles (or molecules) for a given volume not to be confused with number fraction, which is defined as the number of molecules of a species n_i divided by the total number of all molecules n_total. Confusion creeps in when the term abundance appears because this term is not precise and requires context as to whether the value refers to the total amount of a species or as a comparison ratio to the whole. Additionally, measured values are also reported as ppmv (parts per million by volume) and should not be confused with concentration. The ‘v’ in this context (ppmv or ppm_v) refers to the volume mixing ratio to differentiate it from other types of mixing ratios (e.g. Schwartz and Warneck, 1995). The purpose of describing these minutiae is to illustrate how easily confusion could occur. Fortunately, we are dealing with gases which allows straightforward calculations to compare measurements. In atmospheric chemistry, the mixing ratio usually refers to the mole ratio (r_i) as shown in Eq. 1 where N_i is the number of moles of species i such that N_i = n_i/Avogadro’s number.

$$r_i=\frac{N_i}{N_{\mathit{\text{total}}}-N_i}$$ (1)

The mole fraction, x_i, is defined in Eq. 2 as:

$$x_i=\frac{N_i}{{\sum }_{i=1}^k{N}_i}=\frac{N_i}{N_{\mathit{\text{total}}}}$$ (2)

If N_i ≪ N_total, then r_i is almost identical (r_i ≈ x_i) to the mole fraction, x_i. This is particularly true if N_i is small which is the case on Venus where CO₂ and N₂ dominate the atmosphere at fractions of ~96.5% and ~3.5%, respectively. Therefore, the mixing ratio on Venus is essentially the mole fraction and represents the same quantity.

For the purposes of this compilation all measurements, unless noted otherwise, are stated as mole fractions for the reasons just described.

2.2. Measurement Errors

The errors shown within the tables reflect what was noted in the original sources. Unfortunately, many sources do not specify the error ranges, whether the error was 1 or 3 sigma or if the error came about due to instrumental bias.

3. Data Tables

• 3.1Noble Gases: Table 2
• 3.2Noble Gas Isotopes and Associated Isotopic Ratios: Table 3
• 3.3Reactive Gases: Table 4
• 3.4Isotopic Ratios of the Reactive Gases: Table 5

Table 2:

Noble gases

Element	Mole Fraction	Error	Altitude	Technique	Instrumenta	Mission	Comment	Reference (w/relevant pages)
He	12 ppm	+24, −8 ppm	< 100 km	Extrapolation	mass spectrometer PV-BNMS (bus) PV-ONMS (orbiter)	Pioneer Venus	Extrapolated from measurements taken above 130km	von Zahn et al. 1983: pp. 325, 406–407 Tables II & XI
He	9 ppm	± 6 ppm	middle to lower atmosphere	Extrapolation	UV spectroscopy	EUVE	Measured He 584 Å, calculated brightness as function of He mixing ratio using radiative transfer code. Extrapolate to lower atmosphere. Error accounts for uncertainty in eddy diffusion.	Krasnopolsky and Gladstone 2005: p. 399
Ne	7 ppm	± 3 ppm	< 100 km	Compiled in situ data	mass spectrometers	Venera 11/12 Pioneer Venus	von Zahn recommended mean value Combination of 3 adopted values (corrected/normalized)	von Zahn et al. 1983: pp. 325, 408–409 Tables II & XII
Ne	10 ppm	-	< 24 km	in situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman et al. 1980a; pp.7886–7887, Table 2
Ne	12 ppm	+5, −3 ppm	23 – 1 km	in situ	mass spectrometers	Venera 11/12	Value reflects 20Ne mixing ratio relative to measured Ar	Istomin et al. 1980b: p. 16
Ne	< 8 ppm	-	51.6 km	in situ	LGC	Pioneer Venus	Sum of all neon peaks	Oyama et al. 1980; p. 7897, Table 2
Ne	10.6 ppm	+31.6–9.6 ppm (3σ) ± 3.7 ppm (1σ)	41.7 km	in situ	LGC	Pioneer Venus	Sum of all neon peaks	Oyama et al. 1980; p. 7897, Table 2
Ne	4.31 ppm	+5.54–3.91 ppm (3σ) ± 0.65 ppm (1σ)	21.6 km	in situ	LGC	Pioneer Venus	Sum of all neon peaks	Oyama et al. 1980; p. 7897, Table 2
Ar	70 ppm	± 25 ppm	< 100 km	Compiled in situ data	mass spectrometers gas chromatograph	Pioneer Venus Venera 11/12	von Zahn recommended mean value Combination of reported values (corrected/normalized) Referenced to 36Ar	von Zahn et al. 1983: pp. 325, 409–410 Tables II & XIII
Ar	70 ppm	+50, −30 ppm	< 25 km	in situ	LNMS	Pioneer Venus	Sum of three Ar isotopes; see Hoffman Ar isotope data below	Hoffman et al. 1980b: pp. 7876, Table 2
Ar	100 ppm	-	26 km to surface	in situ	mass spectrometers	Venera 13/14	Sum of 36Ar, 38Ar, and 40Ar	Istomin et al. 1982: p. 214, Table III
Ar	110 ppm	± 20 ppm	23 – 1 km	in situ	mass spectrometers	Venera 11/12	Sum of 36Ar, 38Ar, and 40Ar Expected sensitivity 1 ppm	Istomin et al. 1980b: p. 15
Ar	150 ppm	± 50 ppm	23 – 1 km	in situ	mass spectrometers	Venera 11/12	Sum of three Ar isotopes Expected sensitivity 1 ppm Value superceded by Istomin et al 1980b.	Istomin et al 1980a: p. 217, Table 1
Ar	60.5 ppm	+39.5–46.8 ppm (3σ) ± 5.5 ppm (1σ)	51.6 km	in situ	LGC	Pioneer Venus	Value sums Ar isotopes	Oyama et al. 1980: p. 7897, Table 2
Ar	63.8 ppm	± 13.6 ppm (3σ) ± 1.6 ppm (1σ)	41.7 km	in situ	LGC	Pioneer Venus	Value sums Ar isotopes	Oyama et al. 1980: p. 7897, Table 2
Ar	67.2 ppm	± 2.3 ppm (3σ) ± 0.3 ppm (1σ)	21.6 km	in situ	LGC	Pioneer Venus	Value sums Ar isotopes	Oyama et al. 1980: p. 7897, Table 2
Ar	40 ppm	± 20 ppm	< 42 km	in situ	gas chromatograph	Venera 12	Eight atmospheric samples Results presented as(4±2) × 10−3 %	Gel’man et al. 1979: Table 1
Kr	0.05 ppm	± 0.025 ppm	< 100 km	Compiled in situ data	LNMS	Pioneer Venus	No clear choice between the two Kr data measurements; discussed in von Zahn reference Note 84Kr values	von Zahn et al. 1983: pp. 410–412 Tables II & XIV
	0.7 ppm	± 0.35 ppm	< 100 km	Compiled in situ data	mass spectrometers	Venera 11/12
Kr	47 ppb	+22, −35 ppb	< 30 km	in situ	LMNS	Pioneer Venus	Sum of 80−84Kr Upper limit 69 ppb Measured relative to 36Ar	Donahue et al 1981: pp. 514–515 Donahue and Pollack 1983: Table I
Xe	< 40 ppb	-	< 30 km	in situ derived	LNMS	Pioneer Venus	Sum of 128–132Xe Upper limit 120 ppb Values derived from data gathered and influenced by conflicting results on krypton	Donahue et al 1981: pp. 513–514

^aAcronyms: BNMS - Bus Neutral Mass Spectrometer; ONMS - Orbiter Neutral Mass Spectrometer; LNMS – Large probe Neutral Mass Spectrometer; LGC - Large probe Gas Chromatograph

Table 3:

Noble gas isotopes and associated isotopic ratios

Element	Mole Fraction	Error	Altitude	Technique	Instrumenta	Mission	Comment	Reference (w/relevant pages)
3He/4He	< 3 × 10−4	-	< 24 km	in situ	LNMS	Pioneer Venus	Upper limit value; see discussion in references Calculated from ratio: 3He ≈ 3.6 ppb	Hoffman et al. 1980a; p. 7887, Table 3 von Zahn et al. 1983: p. 426, Table XVI
20Ne	9 ppm	-	< 24 km	in situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman et al. 1980a; p. 7887, Table 2
20Ne	10 – 15 ppm	-	23 to 1.5 km	in situ	mass spectrometers	Venera 11/12	Expected instrument sensitivity 5 ppm	Istomin et al. 1980a: p. 217
20Ne	~10 ppm	-	26 km to surface	in situ	mass spectrometers	Venera 13/14		Istomin et al. 1982: p. 213
22Ne	1 ppm	-	< 24 km	in situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman et al. 1980a; p. 7887, Table 2
22Ne/20Ne	0.07	± 0.02 (1σ)	~62 km	in situ	LNMS	Pioneer Venus	Measured in enriched noble gas sample via the isotope ratio measurement cell (IRMC)	Hoffman et al. 1980a; p. 7887, Table 3
20Ne/22Ne	11.8	± 0.7	< 25 km	in situ	mass spectrometer	Pioneer Venus		Donahue 1986: p. 196
20Ne/22Ne	11.9	± 0.7 (1σ)	26 km to surface	in situ	mass spectrometer	Venera 13	1st in situ cycle of Venus 13 MX-6411	Istomin et al. 1982: p. 213, Table II
20Ne/22Ne	11.7	± 0.7 (1σ)	26 km to surface	in situ	mass spectrometer	Venera 13	3rd in situ cycle of Venus 13 MX-6411	Istomin et al. 1982: p. 213, Table II
20Ne/36Ar	0.3	± 0.2	< 24 km	in situ	LNMS	Pioneer Venus		Hoffman et al. 1980a; p. 7887, Table 3
21Ne/22Ne	< 0.067	-	< 100 km	theory			Noted as common planet origin hypothesis	Baines et al 2013: p. 146, Table 1
22Ne/21Ne	< 10	-	26 km to surface	in situ	mass spectrometers	Venera 13/14	Estimate based on raw telemetry	Istomin et al. 1982: p. 214
21Ne/22Ne	< 0.06	-	< 100 km	theory				Donahue 1986: p. 196
36Ar	13 ppm	-	~ 135 km	in situ	mass spectrometer PV-BNMS	Pioneer Venus	Upper limit Relative to CO2	Mauersberger et al. 1979: p. 672
40Ar	28 ppm	-	~ 135 km	in situ	mass spectrometer PV-BNMS	Pioneer Venus	Upper limit Relative to CO2	Mauersberger et al. 1979: p. 672
36Ar	< 9 ppm	-	< 100 km	extrapolation	mass spectrometer PV-BNMS	Pioneer Venus	Upper limit; see 135km data Relative to CO2	Mauersberger et al. 1979: p. 673
40Ar	< 20 ppm	-	< 100 km	extrapolation	mass spectrometer PV-BNMS	Pioneer Venus	Upper limit; see 135km data Relative to CO2	Mauersberger et al. 1979: p. 673
36Ar	31 ppm	± 12 ppm	< 100 km	Compiled in situ data	mass spectrometers	Venera 11/12, Pioneer Venus	von Zahn recommended value Combines reported values with relative 36Ar abundance of 44.2% to [Ar] on Venus	von Zahn et al. 1983: pp. 410, 424, 428 Tables XIII & XVI
36Ar	30 ppm	+20, −10 ppm	< 24 km	in situ	LNMS	Pioneer Venus	Abundance relative to CO2	Hoffman et al. 1980a: pp.7886–7887, Table 2
38Ar	6 ppm	-	< 24 km	in situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman et al. 1980a: pp.7886–7887, Table 2
40Ar	31 ppm	-	< 24 km	in situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman et al. 1980a: pp.7886–7887, Table 2
40Ar	33 ppm	+22, −11 ppm	< 25 km	in situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman et al. 1980b: pp.7876–7877, Table 2
36Ar	63 ppm	see comment	< 24 km	in situ	mass spectrometers	Venera 11/12	Originally reported as 42±2% of total Ar (Artotal= 150±50ppm)	Istomin et al. 1980a: p. 217
38Ar	12 ppm	see comment	< 24 km	in situ	mass spectrometers	Venera 11/12	Originally reported as 8±2% of total Ar (Artotal= 150±50ppm)	Istomin et al. 1980a: p. 217
40Ar	75 ppm	see comment	< 24 km	in situ	mass spectrometers	Venera 11/12	Originally reported as 50±2% of total Ar (Artotal= 150±50ppm) 40Ar abundance = 36Ar+38Ar	Istomin et al. 1980a: p. 217
38Ar/36Ar	0.18	± 0.02	< 24 km	in situ	LNMS	Pioneer Venus		Hoffman et al. 1980a: pp.7886–7887, Table 3
38Ar/36Ar	0.197	± 0.002	23 – 1 km	in situ	mass spectrometers	Venera 11/12	Originally reported as 36Ar/38Ar (5.07±0.05) Expected instrument sensitivity 1ppm	Istomin et al 1980b: pp. 4, 15
40Ar/36Ar	1.03	± 0.04	< 24 km	in situ	LNMS	Pioneer Venus		Hoffman et al. 1980a: pp.7886–7887, Table 3
84Kr	0.6 ppm	± 0.2 ppm	23 – 1 km	in situ	mass spectrometers	Venera 11/12	Relative to Ar	Istomin et al. 1980b: p. 16
84Kr	0.5 – 0.8 ppm	-	23 – 1.5 km	in situ	mass spectrometers	Venera 11/12	Expected instrument sensitivity 1 ppm	Istomin et al. 1980a: p. 217
84Kr	25 ppb	+3, −18 ppb	< 30 km	in situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Donahue et al 1981: p. 515 Donahue and Pollack 1983: Table I
84Kr	10 – 100 ppb	-	26 km to surface	in situ	mass spectrometer	Venera 13	Preliminary results	Istomin et al. 1982: p. 214
84Kr	< 0.2 ppm	-	< 24 km	in situ	LNMS	Pioneer Venus	Upper limit mixing ratio if 36Ar is 30 ppm	Hoffman et al. 1980a: p. 7887, Table 2
83Kr	7.2 ppb	-	< 30 km	in situ	LNMS	Pioneer Venus	Range 0 – 19 ppb Measured relative to 36Ar	Donahue et al 1981: p. 515
82Kr	12.2 ppb	-	< 30 km	in situ	LNMS	Pioneer Venus	Range 6 – 17 ppb Measured relative to 36Ar	Donahue et al 1981: p. 515
80Kr	3.6 ppb	-	< 30 km	in situ	LNMS	Pioneer Venus	Range 0 – 10.2 ppb Measured relative to 36Ar	Donahue et al 1981: p. 515
86Kr	4.3 ppb	-	< 30 km	in situ	LNMS	Pioneer Venus	Upper limit 9 ppb Measured relative to 36Ar	Donahue et al 1981: p. 515
84Kr/36Ar	0.004	± 0.002 (1σ)	< 24 km	in situ	LNMS	Pioneer Venus	Based on total 84 amu peak	Hoffman et al. 1980a: p. 7887, Table 2
131+132Xe	10 – 100 ppb	-	26 km to surface	in situ	mass spectrometer	Venera 14	Preliminary results	Istomin et al. 1982: p. 215
128Xe	1.5 ppb	-	< 30 km	in situ	LNMS	Pioneer Venus	Range 0 – 4.7 ppb Measured relative to 36Ar	Donahue et al 1981: p. 514
129Xe	9.5 ppb	-	< 30 km	in situ	LNMS	Pioneer Venus	Range 0 – 35 ppb Measured relative to 36Ar	Donahue et al 19817: p. 514
130Xe	4 ppb	-	< 30 km	in situ	LNMS	Pioneer Venus	Range 0 – 10 ppb Measured relative to 36Ar	Donahue et al 1981: p. 514
131Xe	14 ppb	-	< 30 km	in situ	LNMS	Pioneer Venus	Range 0 – 40 ppb Measured relative to 36Ar	Donahue et al 1981: p. 514
132Xe	10 ppb	-	< 30 km	in situ	LNMS	Pioneer Venus	Range 0 – 47 ppb Measured relative to 36Ar	Donahue et al 1981: p. 514
132Xe	1.9 ppbv	-	all	computed			Implied from 84Kr/132Xe value as cited in Pepin 1991	Pepin 1991: p. 18
84Kr/132Xe	0.004	± 0.002 (1σ)	< 24 km	in situ	LNMS	Pioneer Venus	Based on total 84 amu peak	Hoffman et al. 1980a: p. 7887, Table 2

^aAcronyms: BNMS - Bus Neutral Mass Spectrometer; ONMS - Orbiter Neutral Mass Spectrometer; LNMS – Large probe Neutral Mass Spectrometer; LGC - Large probe Gas Chromatograph

Table 4:

Reactive Gases

Element	Mole Fraction	Error	Altitude	Technique	Instrumenta	Mission	Comment	References (w/relevant pages & tables)
O2	43.6 ppm	+25.2 ppm (3σ) ± 2.9 ppm (1σ)	51.6 km	in situ	LGC	Pioneer Venus	Questioned by von Zahn et al. 1983	Oyama et al. 1980; p.7897, Table 2
O2	16.0 ppm	+7.4 ppm (3σ) ± 0.9 ppm (1σ)	41.7 km	in situ	LGC	Pioneer Venus	Questioned by von Zahn et al. 1983	Oyama et al. 1980; p.7897, Table 2
O2	< 20 ppm	-	< 42 km	in situ	gas chromatograph	Venera 12	Originally written as 0.002% Estimate due to instrument caveats	Gel’man et al. 1979: p. 5
O2	< 30 ppm	-	52 km	in situ	LNMS	Pioneer Venus	Sample taken prior to clogged inlet	Hoffman et al. 1980b: pp. 7878, Table 2
O2	< 30 ppm	-	22 km	in situ	LNMS	Pioneer Venus	Value is an upper limit due to subtractions of various contributions	Hoffman et al. 1980b: pp. 7878, Table 2
O2	< 50 ppm	-	< 60 km	calculated	scanning spectrophotometers	Venera 12	Discussed in reference §2.5; upper limit added	Moroz 1981: Space Sci Rev. p 20, Table VI (value not cited in orig ref Moroz 1979a)
N2	3.5 %	± 0.8 %	< 100 km	Compiled in situ data	mass spectrometers gas chromatographs	Pioneer Venus Venera 11/12	Value recommended for < 45 km Potentially varies with altitude	von Zahn et al. 1983: p. 359, Table II & V
N2	5.38 v%	± 0.29 v% (1σ)	60–70 km	Remote data	neutron spectrometer	MESSENGER	Supports possible N2 discontinuity at ~45km	Peplowski and Lawrence 2016: Abstract discussion
N2	4 %	± 0.2 %	< 24 km	in situ	LNMS	Pioneer Venus		Hoffman et al. 1980a: p. 7888, Table 2
N2	4.60 %	± 0.14% (3σ) ± 0.02% (1σ)	51.6 km	in situ	LGC	Pioneer Venus	Noted as most accurately determined component within this instrument	Oyama et al. 1980; p.7896, Table 2
N2	3.54 %	± 0.04% (3σ) ± 0.005% (1σ)	41.7 km	in situ	LGC	Pioneer Venus	Noted as most accurately determined component within this instrument	Oyama et al. 1980; p.7896, Table 2
N2	3.41 %	± 0.01% (3σ) ± 0.002% (1σ)	21.6 km	in situ	LGC	Pioneer Venus	Noted as most accurately determined component within this instrument	Oyama et al. 1980; p.7896, Table 2
N2	2.5 %	± 0.5%	< 42 km	in situ	gas chromatograph	Venera 12	Eight atmospheric samples	Gel’man et al. 1979: Table 1
N2	4.5 %	± 1.3%	< 100 km	extrapolated	mass spectrometer PV-BNMS	Pioneer Venus		von Zahn et al. 1980: p. 7835
N2	~4.0 %	-	26 km to surface	in situ	mass spectrometers	Venera 13/14		Istomin et al. 1982: p. 214
N2	4.0 %	± 0.3%	23 – 1 km	in situ	mass spectrometers	Venera 11/12	A negligible background for methane existed in the regime of the chemically active component analysis	Istomin et al. 1980b: p. 12 (COSPAR XXII)
N2	4.5 %	± 0.5%	23 – 1 km	in situ	mass spectrometers	Venera 11/12	Superseded by value from Istomin 1980b?	Istomin et al. 1980a: p. 216 (COSPAR XXIII)
H2	10 ppm	-	< 140 km	derived from in situ	orbiter ion mass spectrometer	Pioneer Venus	Based on photochemical model	Kumar et al. 1981: abstract
H2	Not detected*	-	52–22 km	in situ	LGC	Pioneer Venus, L	If present, upper limit < 10 ppm	Oyama et al. 1980; p.7898, Table 3
H2O	30 ppmv	±15 ppmv	0–45 km	See comment			In depth discussion; commonly cited value	Taylor et al. 1997. in Venus II pp.336–341, Table II
H2O	30 ppm	± 6 ppm	33 km	Remote data	Fourier Transform Spectrometer	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission spectra	Pollack et al. 1993: Table IV
H2O	30 ppm	± 7.5 ppm	23.5 km	Remote data	Fourier Transform Spectrometer	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission spectra	Pollack et al. 1993: Table IV
H2O	30 ppm	±10 ppm	12 km	Remote data	Fourier Transform Spectrometer	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission spectra	Pollack et al. 1993: Table IV
H2O	3.5 – 15 ppm	-	0	Remote data	Fourier Transform Spectrometer	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission spectra	Pollack et al. 1993: Table IV
H2O	40 ppm	-	≤ 55km	Remote data	Fourier Transform Spectrometer	Earth based Telescope	Used best-fit spectrum model Mixing ratio presented as 4×10−5	Bézard et al. 1990:p. 510, Table 1
H2O	30 ppm	+15, −10 ppm	30–40 km	Remote data	Fourier Transform spectrometer	Earth based Telescope	High resolution, NIR Venus night side 2.3 μm window	de Bergh et al. 1995: p. 81
H2O	30 ppm	±10 ppm	15–25 km	Remote data	Fourier Transform spectrometer	Earth based Telescope	High resolution, NIR Venus night side 1.74 μm window	de Bergh et al. 1995: p. 82
H2O	30 ppm	±15 ppm	0–15 km	Remote data	Fourier Transform spectrometer	Earth based Telescope	High resolution, NIR Venus night side 1.1–1.3 μm window	de Bergh et al. 1995: p. 82
H2O	20 ppm	-	surface	in situ	Photometers	Venera 11/12	Refinement of previous data	Moroz et al. 1979: p. 612
H2O	100 ppm	-	< 55 km	selected value (see comment)	photometers gas chromatographs mass spectrometers	Venera 9,10,11,12 Pioneer Venus	Paraphrased from text […likely correct value. The extent to which the various deviations from this mean value result from natural variability instrumental difficulties remains unknown.] Value chosen based on Moroz optical method, models by Pollack et al., and Craig et al. (see von Zahn refs therein)	von Zahn et al. 1983: pp. 370–375, Table III, VII
H2O	0.135%	± 0.015% (3σ) ± 0.002% (1σ)	21.6 km	in situ	LGC	Pioneer Venus	Data potentially skewed by trapped sulfuric acid droplet	Oyama et al. 1980; p.7896, Table 2
H2O	0.519%	± 0.068% (3σ) ± 0.008% (1σ)	41.7 km	in situ	LGC	Pioneer Venus	Data potentially skewed by trapped sulfuric acid droplet	Oyama et al. 1980; p.7896, Table 2
H2O	< 0.06%	-	51.6 km	in situ	LGC	Pioneer Venus	Data potentially skewed by trapped sulfuric acid droplet	Oyama et al. 1980; p.7896, Table 2
H2O	< 0.1%	-	< 52 km	in situ	LN mass spectrometer	Pioneer Venus	Upper limit only	Hoffman et al. 1980b: pp. 7879, Table 2
H2O	31 ppmv	± 2 ppmv (1σ)	30–40 km	Remote data	IR spectra (VIRTIS-H)	Venus Express	dispersion order 5,6; 2.3 μm window	Marcq et al. 2008: p. 7, §3.2.3
H2O	34 ppm	±10 ppm	32–42 km	Remote data	Fourier Transform spectrometer	Earth based Telescope	Venus night side; 2.34–2.43 μm window • CO mixing ratio of 45 ppm at ~42 km	de Bergh et al. 1991: p. 548
HDO	1.3 ppm	± 0.2 ppm	32–42 km	Remote data	Fourier Transform spectrometer	Earth based Telescope	Venus night side; 2.34–2.43 μm window CO mixing ratio of 45 ppm at ~42 km	de Bergh et al. 1991: p. 548
CO2	96.5 %	± 0.8 %	< 100 km	selected value (see comment)	-	-	Typically quoted value Based on previous N2 measurements From text: [Assume that ratio n(N2)/n(CO) is constant throughout the lower and middle atmosphere (hut little observational support)]	von Zahn et al. 1983: pp. 336–336, Table II
CO2	96.4%	± 1.0% (3σ) ± 0.1% (1σ)	21.6 km	in situ	LGC	Pioneer Venus		Oyama et al. 1980; p.7895, Table 2
CO2	95.9%	+4.1%, −5.8% (3σ) ± 0.7% (1σ)	41.7 km	in situ	LGC	Pioneer Venus		Oyama et al. 1980; p.7895, Table 2
CO2	95.4%	+14.6%, −20.1% (3σ) ± 2.5% (1σ)	51.6 km	in situ	LGC	Pioneer Venus		Oyama et al. 1980; p.7895, Table 2
CO	45 ppm	±10 ppm	cloud layer	Remote data	Interferometer	Earth based Telescope	Reported as CO/CO2 ratio of 45 ppm Value at the ‘reflecting layer’	Connes et al. 1968: p. 742
CO	51 ppm	± 1 ppm (1σ)	cloud layer	Remote data	IR spectra	Earth based	A review of Earth-based spectra. Reanalysis of Connes et al. 1968 data Presumes well-mixed atmosphere	Young 1972: p. 654
CO	30 ppm	-	≤ 22 km	Remote data	Fourier Transform Spectrometer	Earth based Telescope	Used best-fit spectrum model Mixing ratio noted originally as 3×10−5	Bézard et al. 1990: p. 510, Table 1
CO	45 ppm	-	42 km	Remote data	Fourier Transform Spectrometer	Earth based Telescope	Used best-fit spectrum model Mixing ratio noted originally as 4.5×10−5	Bézard et al. 1990: p. 510, Table 1
CO	32.2 ppm	+61.7, −22.2 ppm (3σ) ± 7.2 ppm (1σ)	51.6 km	in situ	LGC	Pioneer Venus	Direct measurement	Oyama et al. 1980; p.7897, Table 2
CO	30.2 ppm	± 18 ppm (3σ) ± 2.1 ppm (1σ)	41.7 km	in situ	LGC	Pioneer Venus	Direct measurement	Oyama et al. 1980; p.7897, Table 2
CO	19.9 ppm	± 3.12 ppm (3σ) ± 0.4 ppm (1σ)	21.6 km	in situ	LGC	Pioneer Venus	Direct measurement	Oyama et al. 1980; p.7897, Table 2
CO	28 ppm	± 14 ppm	< 42 km	in situ	gas chromatography	Venera 12	Eight atmospheric samples Results presented as (2.8±1.4)×10−3 %	Gel’man et al. 1979: Table 1
CO	24 – 2 ppmv	± 3, 2 ppmv (1σ) respectively	36 km	Remote data	IR spectra (VIRTIS-H)	Venus Express	latitudinal variability dispersion order 6; 2.3 μm window	Marcq et al. 2008: p. 6, §3.2.1
CO	13.8 – 33.2 ppmv	± 4 ppmv	36 km	Modeled from Remote data	IR spectra (VIRTIS-M-IR)	Venus Express	possible variability in troposphere band ratio technique; 2.3 μm window	Tsang et al. 2009: p. 436, §2.2.3
CO	23 ppm	± 5 ppm	36 km	Remote data	Fourier Transform Spectrometer	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission spectra Gradient: 1.20 ± 0.45 ppm/km	Pollack et al. 1993: Table IV
CO	17 ppmv	± 1 ppmv	12 km	in situ	gas chromatography	Venera 11/12		Marov et al 1989. In The Planet Venus, pp. 25–67. Noted in LF1998
COS [sic]	40 ppmv	± 20 ppmv	29–37 km	in situ	gas chromatography	Venera 13/14	(4±2)·10−3 volume concentration, %	Mukhin et al. 1983: Table 2, p 171
OCS	4.4 ppm	± 1 ppm	33 km	Remote data	Fourier Transform Spectrometer	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission spectra Gradient: −1.58 ± 0.30 ppm/km	Pollack et al. 1993: Table IV
OCS	0.25 ppm	-	≤ 50 km	Remote data	Fourier Transform Spectrometer	Earth based telescopes	Used best-fit spectrum model Mixing ratio noted originally as 2.5×10−7	Bézard et al. 1990: p. 511, Table 1
OCS	14 ppmv	6 ppmv	30 km	Remote data	IR spectra	Earth based telescopes		Bézard 1994. Comunication at the 30th COSPAR Scientific Assembly; Cited in Taylor et al in Venus II, p. 347
OCS	0.35 ppmv	± 0.1 ppmv	38 km	Remote data	IR spectra	Earth based telescopes		Bézard 1994. Comunication at the 30th COSPAR Scientific Assembly; Cited in Taylor et al in Venus II.p. 347
OCS	2.5 – 4 ppmv	± 1 ppmv (1σ)	33 km	Remote data	IR spectra (VIRTIS-H)	Venus Express	latitudinal variability; CO anticorrelated dispersion order 5,6; 2.3μm window	Marcq et al. 2008: p. 7, §3.2.2
OCS	*Not detected	-	52–22 km	in situ	LGC	Pioneer Venus	If present, upper limit < 2 ppm	Oyama et al. 1980; p.7898, Table 3
OCS	< 3 ppm	-	> 24 km	in situ	LNMS	Pioneer Venus	Debatable data due to sulfuric acid droplet	Hoffman et al. 1980a; p. 7886, Table 2
OCS	< 500 ppm	-	< 20 km	in situ	LNMS	Pioneer Venus	Debatable data due to sulfuric acid droplet	Hoffman et al. 1980a; p. 7886, Table 2
SO2	4 ppm	-	58 km	model	UV spectrometer	Pioneer Venus	Model constrained using PV-OUVS data	Winick and Stewart 1980: p. 7854
SO2	180 ppm	± 70 ppm	42 km	Remote data	Fourier Transform Spectrometer	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission spectra	Pollack et al. 1993: Table IV
SO2	130 ppmv	± 50 ppmv (1σ)	35 km	Remote data	IR spectra (VIRTIS-H)	Venus Express	dispersion order 5,6; 2.3 μm window assume uniform abund vertical profile	Marcq et al. 2008: p. 7, §3.2.4
SO2	130 ppm	± 60 ppm	< 42 km	in situ	gas chromatography	Venera 12	Eight atmospheric samples Results presented as (1.3±0.6)×10−2 %	Gel’man et al. 1979: Table 1
SO2	185 ppm	+350, −155 ppm (3σ) ± 43.1 ppm (1σ)	21.6 km	in situ	LGC	Pioneer Venus		Oyama et al. 1980; p.7898, Table 2
SO2	176 ppm	+2000, 0 ppm (3σ) + 296, 0 ppm (1σ)	41.7 km	in situ	LGC	Pioneer Venus		Oyama et al. 1980; p.7898, Table 2
SO2	< 600 ppm	-	51.6 km	in situ	LGC	Pioneer Venus		Oyama et al. 1980; p.7898, Table 2
SO2	< 300 ppm	-	< 24 km	in situ	LNMS	Pioneer Venus	Upper limit value due to clogged inlet	Hoffman et al. 1980a: pp. 7888–7889, Table 2
SO2	<10 ppm	-	55 km	in situ	LNMS	Pioneer Venus		Hoffman et al. 1980a: pp. 7888–7889, Table 2
SO2	150 ppm	-	52 km	in situ	UV spectrometer	VEGA 1	Gradient discussed	Bertaux et al. 1996: p. 12737, Table 4
SO2	65 ppm	-	52 km	in situ	UV spectrometer	VEGA 2	Gradient discussed	Bertaux et al. 1996: p. 12737, Table 4
SO2	125 ppm	-	42 km	in situ	UV spectrometer	VEGA 1	Gradient discussed	Bertaux et al. 1996: p. 12737, Table 4
SO2	140 ppm	-	42 km	in situ	UV spectrometer	VEGA 2	Gradient discussed	Bertaux et al. 1996: p. 12737, Table 4
SO2	38 ppm	-	22 km	in situ	UV spectrometer	VEGA 1	Gradient discussed	Bertaux et al. 1996: p. 12737, Table 4
SO2	38 ppm	-	22 km	in situ	UV spectrometer	VEGA 2	Gradient discussed	Bertaux et al. 1996: p. 12737, Table 4
SO2	25 ppm	± 2 ppm	12 km	in situ	UV spectrometer	VEGA 1	Gradient discussed	Bertaux et al. 1996: p. 12737, Table 4
SO2	20 ppm	-	12 km	in situ	UV spectrometer	VEGA 2	Gradient discussed	Bertaux et al. 1996: p. 12737, Table 4
SO2	130 ppm	± 40 ppm	35–45 km	Remote data	spectrometer	Earth based	Venus nightside emission; 2.3 μm window	Bézard et al. 1993: p. 1588
SO2	150 ppm	-	22 km	Compiled in situ data	UV spectrometer mass spectrometers gas chromatograph	Venera 12 Pioneer Venus	von Zahn recommended value	von Zahn et al. 1983: pp. 390–392, Tables III & X
SO2	<10 ppm	-	55 km	Compiled in situ data	UV spectrometer mass spectrometers gas chromatograph	Venera 12 Pioneer Venus	von Zahn recommended value	von Zahn et al. 1983: pp. 390–392, Tables III & X
SO2	*Not detected	-	23 – 4 km	in situ	mass spectrometers	Venera 11/12	If present, upper limit < 25 ppm	Istomin et al. 1980b: p. 17
SO	20 ppb	± 10 ppb	cloud-top	Remote data	LWP Camera	Intl UV Explorer		Na et al. 1990: abstract & p. 7490
H2S	3 ppm	± 2 ppm	< 24 km	in situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman et al. 1980a: pp. 7789, Table 2
H2S	Not detected*	-	52–22 km	in situ	LGC	Pioneer Venus	If existent, upper limit < 2 ppm	Oyama et al. 1980; p.7898, Table 3
H2SO4	8 ppmv	-	46 km	Remote data	microwave: VLA	Earth based	Rapidly declines below this altitude	Jenkins et al. 2002: p.324
CH4	Not detected*	-	22–52 km	Data	LGC	Pioneer Venus	If present, upper limit < 0.6 ppm	Oyama et al. 1980; p.7898, Table 3
CH4	980 ppm	-	> 50 km	in situ	LNMS	Pioneer Venus	Observation questioned; no plausible explanation. See discussion in reference.	Donahue and Hodges 1993: p. 592
CH4	2800 ppm	-	Near surface	in situ	LN mass spectrometer	Pioneer Venus	Observation questioned; no plausible explanation. See discussion in reference.	Donahue and Hodges 1993: p. 592
CH4	< 0.1 ppm	-	30 km	Remote data	spectrometers	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission IR spectra	Pollack et al. 1993: Table IV
CH4	< 2.0 ppm	-	24 km	Remote data	spectrometers	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission IR spectra	Pollack et al. 1993: Table IV
C2H4	Not detected*	-	22–52 km	in situ	LGC	Pioneer Venus	If existent, upper limit < 1 ppm	Oyama et al. 1980; p.7898, Table 3
C2H6	~2 ppm	-	< 24 km	in situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman et al. 1980a: pp. 7789, Table 2
C2H6	Not detected*	-	22–52 km	in situ	LGC	Pioneer Venus	If existent, upper limit < 1 ppm	Oyama et al. 1980; p.7898, Table 3
C3H6	Not detected*	-	22–52 km	in situ	LGC	Pioneer Venus	If existent, upper limit < 5 ppm	Oyama et al. 1980; p.7898, Table 3
Cl	<10 ppm	-	< 24 km	in situ	LNMS	Pioneer Venus	Upper limit; deduced from measurements.	Hoffman et al. 1979b: p. 50 Hoffman et al. 1980a: Table 2
HCl	0.1 ppm	± 0.03 ppm (1σ)	70–75 km	Remote data	SOIR	Venus Express	orbit 136	Bertaux et al. 2007: p. 648
HCl	0.17 ppm	± 0.03 ppm (1σ)	70–75 km	Remote data	SOIR	Venus Express	orbit 247	Bertaux et al. 2007: p. 648
HCl	0.4 ppmv	-	cloud-top	Remote data	Fourier Transform Spectrometer	CFHT Earth based	Altitude at 35mbar level	de Bergh et al. 1989: abstract 6.09P
HCl	0.5 ppm	-	~18 km	Remote data	Fourier Transform Spectrometer	Earth based telescopes	Used best-fit spectrum model Mixing ratio presented as 5×10−7	Bézard et al. 1990: p. 511, Table 1
HCl	0.48 ppm	± 0.12 ppm	23.5 km	Remote data	spectrometers	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission spectra	Pollack et al. 1993: Table IV
HCl	0.4 ppm	-	~64 km	model			Value based on chemical modelling and related observations	von Zahn et al. 1983: pp. 401–403, Table III
HCl	0.5 ppmv	± 0.15 ppmv	15–30 km	Remote data	IR spectra	Earth based		Bézard 1994. Communication at the 30th COSPAR Scientific Assembly; Cited in Taylor et al in Venus II.p. 347
HF	0.005 ppm	-	~64 km	model			Based on chemical modelling and related observations	von Zahn et al. 1983: p. 403, Table III; Parisot and Moreels 1984: p. 73
HF	0.001–0.003 ppb	-	75–85 km	Remote data	SOIR	Venus Express	orbit 114	Bertaux et al. 2007: p. 648
HF	5 ppbv	± 2 ppbv	30–40 km	Remote data	IR spectra	Earth based		Bézard 1994. Communication at the 30th COSPAR Scientific Assembly; Cited in Taylor et al in Venus II.p. 347
HF	0.001–0.005 ppm	-	33.5	Remote data	Fourier Transform Spectrometer	Earth based telescopes	Radiative transfer program/model with two Venus nightside emission spectra	Pollack et al. 1993: Table IV
HF	4.5 ppb 0.0045 ppm	-	~32 km	Remote data	Fourier Transform Spectrometer	Earth based Telescope	Used best-fit spectrum model Mixing ratio presented as 4.5×10−9	Bézard et al. 1990: p. 510, Table 1
N2O	*Not detected	-	22–52 km	in situ	LGC	Pioneer Venus	If present, upper limit < 10 ppm; optimum case	Oyama et al. 1980; p.7898, Table 3
Hg	*Not detected	-	< 24 km	in situ	LNMS	Pioneer Venus	Upper limit of 5ppm reported but discussion implies uncertain detection.	Hoffman et al. 1980a: pp. 7789, Table 2

^aAcronyms: BNMS - Bus Neutral Mass Spectrometer; ONMS - Orbiter Neutral Mass Spectrometer; LNMS – Large probe Neutral Mass Spectrometer; LGC - Large probe Gas Chromatograph

Table 5:

Isotopic Ratios of the Reactive Gases

Element	Ratio	Error	Altitude	Technique	Instrument	Mission	Comment	References (w/relevant pages & tables)
D/H in H2O	0.016	± 0.002	~54 km	in situ	mass spectrometer LNMS	Pioneer Venus	Measured when inlets were clogged with H2SO4 droplets	Donahue et al. 1982: p. 630, 633
D/H in H2O	0.019	± 0.006	32–42 km	Remote data	Fourier Transform spectrometer	Earth based Telescope	Venus night side; 2.34–2.43 μm window CO mixing ratio of 45 ppm at ~42 km D/H equal to ½ × [HDO]/[H2O]	de Bergh et al. 1991: p. 548
D/H	0.025	± 0.005	54 km	in situ	Mass Spectrometer	Pioneer Venus	Derived from H2SO4 droplets trapped at 54km	Atreya, personal communication
12C/13C in CO2	86	± 12	Cloud tops	Remote data	Michelson Interferometer	Earth-based	Derived from 13CO2 abundance	Bézard et al. 1987: p.623 & Table IV
12C/13C in CO2	89.3	± 1.6	23 – 1 km	in situ	mass spectrometers	Venera 11/12	Presented as 13C/12C: 1.12±0.02 × 10−2 Includes contributions from CH+ ions	Istomin et al. 1980b: p. 13
12C/13C in CO2	84.0	± 4.2	23 – 1 km	in situ	mass spectrometer LNMS	Pioneer Venus	Presented as 13C/12C ≤ 1.19±0.06 × 10−2	Hoffman et al. 1980a; p. 7887, Table 3
14N/15N	Earth atmos value	± 20%	< 100 km	in situ derive	Mass Spectrometer	Pioneer Venus	Assumes well mixed atmosphere. 14N/15N = 273 ± 56; see ref note	Hoffman et al 1979: abstract Value in Lodders&Fegley 1998: Table 5.5
l8O/16O	2.0 × 10−3	± 0.1 × 10−3	< 24 km	in situ	mass spectrometer LNMS	Pioneer Venus	Contributions from CO2 and SO2	Hoffman et al. 1980a; p. 7888, Table 3
l8O/16O in CO2	0.002	± 0.0125	Cloud tops	Remote data	Michelson Interferometer	Earth-based	Derived from 12C16O18O abundance Reported as 16O/18O= 500± 80	Bézard et al. 1987: p. 623 & Table V
35Cl/37Cl in HCl	2.9	± 0.3	Cloud tops	Remote data	IR spectra	Earth-based	Primary data presented in Connes et al. 1967. Calculated from HCl lines in the 2–0 R-Branch (Table 1, p.1231) [value 2.869]	Cited value Young 1972: p. 640; Connes et al. 1967 orig data

^aAcronyms: LNMS – Large probe Neutral Mass Spectrometer

4. Summary

These Tables are by no means the last word on Venus atmospheric data, both measured and modelled, but rather provide a useful overall reference for future work. We look forward to obtaining new information about Venus’ atmosphere from the cloud-tops to the surface and the exciting, new missions that hopefully, will eventually and inevitably be sent to Venus.