Venus Atmospheric Composition In Situ Data: A Compilation

Abstract

The Venus atmosphere is of significant interest yet only rudimentary solid data have 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 nonnoble 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.

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 originate 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 subsonic which typically occurred below 64 km in almost all of the cases. More recent data were obtained through remote Earth‐based, flyby or orbiter observations. Tables  and list the spacecraft and Earth/space‐based facilities that have gathered data about Venus and whose data are reflected in this compilation.

Missions to Venus and Spacecraft That Returned Venus Data

Date launched	Name (nation)	Type	Venus date (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 65 min from surface; surface images
20 May 1978	Pioneer Venus 1 (USA)	Orbiter	4 Dec 1978 (n/a)	Radar map 73°N/63°S at 75‐km resolution; in operation for ~14 years
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 min 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 min
4 Nov 1981	Venera 14 (USSR)	Flyby/Lander	5 Mar 1982 (13.25°S, 310°)	Lander relayed data for 57 min 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 atmospheric data (survived 46.5 hr); lander relayed data for 56 min
21 Dec 1984	VeGa 2 (USSR)	Flyby/Probe/Lander	15 Jun 1985 (6.45°S, 181.08°)	Balloon‐gondola gathered atmospheric data (survived 46.5 hr); lander relayed data for 57 min
4 May 1989	Magellan (USA)	Orbiter	10 Aug 1990 (n/a)	Radar mapping; 98% coverage; remained in orbit ~4 years
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, atmospheric studies; final mission duration ~9 years
20 May 2010	Akatsuki (Japan)	Orbiter	7 Dec 2015 (n/a)	Failed initial orbit 2010 insertion; atmospheric dynamics and cloud physics; ongoing

Mission design and operation: NASA (USA), Lavochkin (USSR), ESA (Europe), JAXA (Japan). Date of flyby/entry/landing of spacecraft; if known, Venus latitude and longitude of final resting spot.Mission data to 2000 (Siddiqi, ). 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 3.6‐m 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

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. () 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, also known as VIRA (Kliore et al., ), 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 are limited in scope either by vertical resolution, massive error bars, or having no measurements whatsoever, for example, 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.

Methodology

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 modeled data are indicated.

While compiling these 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. (), the reported measurements for each species are provided as mixing ratios: “we provide … mixing ratios x_i = n_i/ ∑ n_i (with n_i being the number density of species i) of all those gases which have been positively identified in Venus' 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 & Warneck, ). The purpose of describing these minutiae is to illustrate how easily confusion could occur. Fortunately, we are dealing with gases which allow straightforward calculations to compare measurements. In atmospheric chemistry, the mixing ratio usually refers to the mole ratio (r_i) as shown in equation , where N_i is the number of moles of species i such that N_i = n_i/Avogadro^′s number. [Image Omitted. See PDF]

The mole fraction, x_i, is defined in equation  as [Image Omitted. See PDF]

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.

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.

Data Tables

Noble Gases: Table  Noble Gases

Element	Mole fraction	Error	Altitude	Technique	Instrument	Mission	Comment	Reference (with 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. (), pp 325, 406–407 Tables 2 and 11
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 (), 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	von Zahn et al. (), pp. 325, 408–409, Tables 2 and 12
• Combination of three adopted values (corrected/normalized)
Ne	10 ppm	‐	< 24 km	In situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman, Hodges, Donahue, et al. (), 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	Istomin et al., (), p. 16
• Relative to measured Ar
Ne	<8 ppm	‐	51.6 km	In situ	LGC	Pioneer Venus	Sum of all neon peaks	Oyama et al. (), 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. (), 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. (), 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	von Zahn et al. (), pp. 325, 409–410 Tables 2 and 13
• Combination of reported values (corrected/normalized)
• Referenced to 36Ar
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, Hodges, Wright, et al. (), 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. (), p. 214, Table 3
Ar	110 ppm	± 20 ppm	23–1 km	In situ	mass spectrometers	Venera 11/12	• Sum of 36Ar, 38Ar, and 40Ar	Istomin et al. (), p. 15
• Expected sensitivity 1 ppm
Ar	150 ppm	± 50 ppm	23–1 km	In situ	mass spectrometers	Venera 11/12	• Sum of three Ar isotopes	Istomin et al. (), p. 217, Table 1
• Expected sensitivity 1 ppm
• Value superceded by Istomin et al. ().
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. (), 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. (), 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. (), p. 7897, Table 2
Ar	40 ppm	± 20 ppm	< 42 km	In situ	gas chromatograph	Venera 12	• Eight atmospheric samples	Gel'man et al. (), Table 1
• Results presented as(4±2) × 10−3 %
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	von Zahn et al. (), pp. 410–412, Tables 2 and 14
0.7 ppm	± 0.35 ppm	< 100 km	Compiled in situ data	mass spectrometers	Venera 11/12
• Note 84Kr values
Kr	47 ppb	+22, −35 ppb	< 30 km	In situ	LMNS	Pioneer Venus	• Sum of 80–84Kr	Donahue et al. (), pp. 514–515; Donahue and Pollack (), p. 1006,  Table 1
• Upper limit 69 ppb
• Measured relative to 36Ar
Xe	< 40 ppb	‐	< 30 km	In situ derived	LNMS	Pioneer Venus	• Sum of 128–132Xe	Donahue et al. (), pp. 513–514
• Upper limit 120 ppb
• Values derived from data gathered and influenced by conflicting results on krypton

BNMS = Bus Neutral Mass Spectrometer, ONMS = Orbiter Neutral Mass Spectrometer, LNMS = Large probe Neutral Mass Spectrometer, LGC = Large probe Gas Chromatograph.

Noble Gas Isotopes and Associated Isotopic Ratios: Table  Noble Gas Isotopes and Associated Isotopic Ratios

Element	Mole fraction	Error	Altitude	Technique	Instrument	Mission	Comment	Reference (with relevant pages)
3He/4He	< 3 × 10−4	‐	< 24 km	In situ	LNMS	Pioneer Venus	• Upper limit value; see discussion in references	Hoffman, Hodges, Donahue, et al. (), p. 7887, Table 3; von Zahn et al. (), p. 426, Table 16
• Calculated from ratio: 3He ≈ 3.6 ppb
20Ne	9 ppm	‐	< 24 km	In situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman, Hodges, Donahue, et al. (), 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. (), p. 217
20Ne	~10 ppm	‐	26 km to surface	In situ	mass spectrometers	Venera 13/14		Istomin et al. (), p. 213
22Ne	1 ppm	‐	< 24 km	In situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman, Hodges, Donahue, et al. (), 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, Hodges, Donahue, et al. (), p. 7887, Table 3
20Ne/22Ne	11.8	± 0.7	< 25 km	In situ	mass spectrometer	Pioneer Venus		Donahue (), p. 196
20Ne/22Ne	11.9	± 0.7 (1σ)	26 km to surface	In situ	mass spectrometer	Venera 13	First in situ cycle of Venus 13 MX‐6411	Istomin et al. (), p. 213, Table 2
20Ne/22Ne	11.7	± 0.7 (1σ)	26 km to surface	In situ	mass spectrometer	Venera 13	Third in situ cycle of Venus 13 MX‐6411	Istomin et al. (), p. 213, Table 2
20Ne/36Ar	0.3	± 0.2	< 24 km	In situ	LNMS	Pioneer Venus		Hoffman, Hodges, Donahue, et al. (), p. 7887, Table 3
21Ne/22Ne	< 0.067	‐	< 100 km	theory			Noted as common planet origin hypothesis	Baines et al. (), 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. (), p. 214
21Ne/22Ne	< 0.06	‐	< 100 km	theory				Donahue (), p. 196
36Ar	13 ppm	‐	~ 135 km	In situ	mass spectrometer PV‐BNMS	Pioneer Venus	• Upper limit	Mauersberger et al. (), p. 672
• Relative to CO2
40Ar	28 ppm	‐	~ 135 km	In situ	mass spectrometer PV‐BNMS	Pioneer Venus	• Upper limit	Mauersberger et al. (), p. 672
• Relative to CO2
36Ar	< 9 ppm	‐	< 100 km	extrapolation	mass spectrometer PV‐BNMS	Pioneer Venus	• Upper limit; see 135‐km data	Mauersberger et al. (), p. 673
• Relative to CO2
40Ar	< 20 ppm	‐	< 100 km	extrapolation	mass spectrometer PV‐BNMS	Pioneer Venus	• Upper limit; see 135‐km data	Mauersberger et al. (), p. 673
• Relative to CO2
36Ar	31 ppm	± 12 ppm	< 100 km	Compiled in situ data	mass spectrometers	Venera 11/12, Pioneer Venus	• von Zahn recommended value	von Zahn et al. (), pp. 410, 424, 428, Tables 13 and 16
• Combines reported values with relative 36Ar abundance of 44.2% to [Ar] on Venus
36Ar	30 ppm	+20, −10 ppm	< 24 km	In situ	LNMS	Pioneer Venus	Abundance relative to CO2	Hoffman, Hodges, Donahue, et al. (), pp.7886–7887, Table 2
38Ar	6 ppm	‐	< 24 km	In situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman, Hodges, Donahue, et al. (), pp.7886–7887, Table 2
40Ar	31 ppm	‐	< 24 km	In situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman, Hodges, Donahue, et al. (), pp.7886–7887, Table 2
40Ar	33 ppm	+22, −11 ppm	< 25 km	In situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman, Hodges, Wright, et al., (), 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. (), 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. (), 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)	Istomin et al. (), p. 217
•40Ar abundance = 36Ar+38Ar
38Ar/36Ar	0.18	± 0.02	< 24 km	In situ	LNMS	Pioneer Venus		Hoffman, Hodges, Donahue, et al. (), 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)	Istomin et al. (), pp. 4, 15
•Expected instrument sensitivity 1ppm
40Ar/36Ar	1.03	± 0.04	< 24 km	In situ	LNMS	Pioneer Venus		Hoffman, Hodges, Donahue, et al. (), 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. (), 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. (), p. 217
84Kr	25 ppb	+3, −18 ppb	< 30 km	In situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Donahue et al. (), p. 515; Donahue and Pollack (), Table 1
84Kr	10–100 ppb	‐	26 km to surface	In situ	mass spectrometer	Venera 13	Preliminary results	Istomin et al. (), p. 214
84Kr	< 0.2 ppm	‐	< 24 km	In situ	LNMS	Pioneer Venus	Upper limit mixing ratio if 36Ar is 30 ppm	Hoffman, Hodges, Donahue, et al. (), p. 7887, Table 2
83Kr	7.2 ppb	‐	< 30 km	In situ	LNMS	Pioneer Venus	• Range 0–19 ppb	Donahue et al. (), p. 515
• Measured relative to 36Ar
82Kr	12.2 ppb	‐	< 30 km	In situ	LNMS	Pioneer Venus	• Range 6–17 ppb	Donahue et al. (), p. 515
• Measured relative to 36Ar
80Kr	3.6 ppb	‐	< 30 km	In situ	LNMS	Pioneer Venus	• Range 0–10.2 ppb	Donahue et al. (), p. 515
• Measured relative to 36Ar
86Kr	4.3 ppb	‐	< 30 km	In situ	LNMS	Pioneer Venus	• Upper limit 9 ppb	Donahue et al. (), p. 515
• Measured relative to 36Ar
84Kr/36Ar	0.004	± 0.002 (1σ)	< 24 km	In situ	LNMS	Pioneer Venus	Based on total 84‐amu peak	Hoffman, Hodges, Donahue, et al. (), p. 7887, Table 2
131+132Xe	10–100 ppb	‐	26 km to surface	In situ	mass spectrometer	Venera 14	Preliminary results	Istomin et al. (), p. 215
128Xe	1.5 ppb	‐	< 30 km	In situ	LNMS	Pioneer Venus	• Range 0–4.7 ppb	Donahue et al. (), p. 514
• Measured relative to 36Ar
129Xe	9.5 ppb	‐	< 30 km	In situ	LNMS	Pioneer Venus	• Range 0–35 ppb	Donahue et al. (), p. 514
• Measured relative to 36Ar
130Xe	4 ppb	‐	< 30 km	In situ	LNMS	Pioneer Venus	• Range 0–10 ppb	Donahue et al., (), p. 514
• Measured relative to 36Ar
131Xe	14 ppb	‐	< 30 km	In situ	LNMS	Pioneer Venus	• Range 0–40 ppb	Donahue et al. (), p. 514
• Measured relative to 36Ar
132Xe	10 ppb	‐	< 30 km	In situ	LNMS	Pioneer Venus	• Range 0–47 ppb	Donahue et al. (), p. 514
• Measured relative to 36Ar
132Xe	1.9 ppbv	‐	All	computed			Implied from 84Kr/132Xe value as cited in Pepin ()	Pepin (), p. 18
84Kr/132Xe	0.004	± 0.002 (1σ)	< 24 km	In situ	LNMS	Pioneer Venus	Based on total 84‐amu peak	Hoffman, Hodges, Donahue, et al. (), p. 7887, Table 2

BNMS = Bus Neutral Mass Spectrometer, ONMS = Orbiter Neutral Mass Spectrometer, LNMS = Large probe Neutral Mass Spectrometer, LGC = Large probe Gas Chromatograph.

Reactive Gases: Table  Reactive Gases

Element	Mole fraction	Error	Altitude	Technique	Instrument	Mission	Comment	References (with relevant pages and 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. ()	Oyama et al. (), 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. ()	Oyama et al. (), p.7897, Table 2
O2	< 20 ppm	‐	< 42 km	In situ	gas chromatograph	Venera 12	• Originally written as 0.002%	Gel'man et al. (), p. 7
• Estimate due to instrument caveats
O2	< 30 ppm	‐	52 km	In situ	LNMS	Pioneer Venus	Sample taken prior to clogged inlet	Hoffman, Hodges, Wright, et al. (), 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, Hodges, Wright, et al. (), pp. 7878, Table 2
O2	< 50 ppm	‐	< 60 km	calculated	scanning spectrophotometers	Venera 12	Discussed in reference section 2.5; upper limit added	Moroz (), Space Sci Rev., p 20, Table 6 (value not cited in orig ref Moroz, Moshkin, et al. ()
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	von Zahn et al. (), p. 359, Tables 2 and 5
• Potentially varies with altitude
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, (), Abstract discussion
N2	4 %	± 0.2 %	< 24 km	In situ	LNMS	Pioneer Venus		Hoffman, Hodges, Donahue, et al., (), 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. (), 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. (), 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. (), p.7896, Table 2
N2	2.5 %	± 0.5%	< 42 km	In situ	gas chromatograph	Venera 12	Eight atmospheric samples	Gel'man et al. (), Table 1
N2	4.5 %	± 1.3%	< 100 km	extrapolated	mass spectrometer PV‐BNMS	Pioneer Venus		von von Zahn et al. (), p. 7835
N2	~4.0 %	‐	26 km to surface	In situ	mass spectrometers	Venera 13/14		Istomin et al. (), 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. (), p. 12 (COSPAR XXII)
N2	4.5 %	± 0.5%	23–1 km	In situ	mass spectrometers	Venera 11/12	Superseded by value from Istomin et al. ()?	Istomin et al. (), 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. (), abstract
H2	Not detected*	‐	52–22 km	In situ	LGC	Pioneer Venus, L	If present, upper limit < 10 ppm	Oyama et al. (), p.7898, Table 3
H2O	30 ppmv	± 15 ppmv	0–45 km	See comment		In depth discussion; commonly cited value	Taylor et al. (). in Venus II pp. 336–341, Table 2
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. (), Table 4
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. (), Table 4
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. (), Table 4
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. (), Table 4
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. (), 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	de Bergh et al. (), p. 81
• 2.3 μm window
H2O	30 ppm	± 10 ppm	15–25 km	Remote data	Fourier Transform spectrometer	Earth based Telescope	• High resolution, NIR Venus night side	de Bergh et al. (), p. 82
• 1.74 μm window
H2O	30 ppm	± 15 ppm	0–15 km	Remote data	Fourier Transform spectrometer	Earth based Telescope	• High resolution, NIR Venus night side	de Bergh et al. (), p. 82
• 1.1–1.3‐μm window
H2O	20 ppm	‐	surface	In situ	Photometers	Venera 11/12	Refinement of previous data	Moroz, Parfent'ev, and Sanko (), 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.]	von Zahn et al. (), pp. 370–375, Tables 3 and 7
• Value chosen based on Moroz optical method, models by Pollack et al., and Craig et al. (see von Zahn refs therein)
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. (), 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. (), 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. (), p.7896, Table 2
H2O	< 0.1%	‐	< 52 km	In situ	LN mass spectrometer	Pioneer Venus	Upper limit only	Hoffman, Hodges, Wright, et al. (), 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. (), p. 7, section 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. (), 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	de Bergh et al. (), p. 548
• CO mixing ratio of 45 ppm at ~42 km
CO2	96.5 %	± 0.8 %	< 100 km	selected value (see comment)	‐	‐	• Typically quoted value	von Zahn et al. (), pp. 336–336, Table 2
• 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)]
CO2	96.4%	± 1.0% (3σ) ± 0.1% (1σ)	21.6 km	In situ	LGC	Pioneer Venus		Oyama et al. (), 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. (), 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. (), 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	Connes et al. (), p. 742
• Value at the “reflecting layer
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. () data Presumes well‐mixed atmosphere	Young (), p. 654
CO	30 ppm	‐	≤ 22 km	Remote data	Fourier Transform Spectrometer	Earth based Telescope	• Used best fit spectrum model	Bézard et al. (), p. 510, Table 1
• Mixing ratio noted originally as 3 × 1−5
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. (), 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. (), 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. (), 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. (), p.7897, Table 2
CO	28 ppm	± 14 ppm	< 42 km	In situ	gas chromatography	Venera 12	• Eight atmospheric samples	Gel'man et al. (), Table 1
• Results presented as (2.8±1.4) × 10−3 %
CO	24–2 ppmv	± 3, 2 ppmv (1σ) respectively	36 km	Remote data	IR spectra (VIRTIS‐H)	Venus Express	• latitudinal variability	Marcq et al. (), p. 6, section 3.2.1
• dispersion order 6; 2.3‐μm window
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	Tsang et al. (), p. 436, section 2.2.3
• band ratio technique; 2.3‐μm window
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	Pollack et al. (), Table 4
• Gradient: 1.20 ± 0.45 ppm/km
CO	17 ppmv	± 1 ppmv	12 km	In situ	gas chromatography	Venera 11/12		Marov et al. (). In The Planet Venus, pp. 25–67. Noted in Lodders and Fegley ()
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. (), 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	Pollack et al. (), Table 4
• Gradient: −1.58 ± 0.30 ppm/km
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. (), p. 511, Table 1
OCS	14 ppmv	6 ppmv	30 km	Remote data	IR spectra	Earth based telescopes		Bézard (). Communication 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 (). Communication 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	Marcq et al. (), p. 7, section 3.2.2
•dispersion order 5,6; 2.3‐μm window
OCS	*Not detected	‐	52–22 km	In situ	LGC	Pioneer Venus	If present, upper limit < 2 ppm	Oyama et al. (), p.7898, Table 3
OCS	< 3 ppm	‐	> 24 km	In situ	LNMS	Pioneer Venus	Debatable data due to sulfuric acid droplet	Hoffman, Hodges, Donahue, et al., (), p. 7886, Table 2
OCS	< 500 ppm	‐	< 20 km	In situ	LNMS	Pioneer Venus	Debatable data due to sulfuric acid droplet	Hoffman, Hodges, Donahue, et al., (), p. 7886, Table 2
SO2	4 ppm	‐	58 km	model	UV spectrometer	Pioneer Venus	Model constrained using PV‐OUVS data	Winick and Stewart (), 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. (), Table 4
SO2	130 ppmv	± 50 ppmv (1σ)	35 km	Remote data	IR spectra (VIRTIS‐H)	Venus Express	• dispersion order 5,6; 2.3μm window	Marcq et al. (), p. 7, section 3.2.4
• assume uniform abundance vertical profile
SO2	130 ppm	± 60 ppm	< 42 km	In situ	gas chromatography	Venera 12	• Eight atmospheric samples	Gel'man et al. (), Table 1
• Results presented as (1.3±0.6) × 10−2 %
SO2	185 ppm	+350, −155 ppm (3σ) ± 43.1 ppm (1σ)	21.6 km	In situ	LGC	Pioneer Venus		Oyama et al. (), 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. (), p.7898, Table 2
SO2	< 600 ppm	‐	51.6 km	In situ	LGC	Pioneer Venus		Oyama et al. (), p.7898, Table 2
SO2	< 300 ppm	‐	< 24 km	In situ	LNMS	Pioneer Venus	Upper limit value due to clogged inlet	Hoffman, Hodges, Donahue, et al., (), pp. 7888–7889, Table 2
SO2	< 10 ppm	‐	55 km	In situ	LNMS	Pioneer Venus		Hoffman, Hodges, Donahue, et al., (), pp. 7888–7889, Table 2
SO2	150 ppm	‐	52 km	In situ	UV spectrometer	VEGA 1	Gradient discussed	Bertaux et al. (), p. 12,737, Table 4
SO2	65 ppm	‐	52 km	In situ	UV spectrometer	VEGA 2	Gradient discussed	Bertaux et al. (), p. 12,737, Table 4
SO2	125 ppm	‐	42 km	In situ	UV spectrometer	VEGA 1	Gradient discussed	Bertaux et al. (), p. 12,737, Table 4
SO2	140 ppm	‐	42 km	In situ	UV spectrometer	VEGA 2	Gradient discussed	Bertaux et al. (), p. 12,737, Table 4
SO2	38 ppm	‐	22 km	In situ	UV spectrometer	VEGA 1	Gradient discussed	Bertaux et al. (), p. 12,737, Table 4
SO2	38 ppm	‐	22 km	In situ	UV spectrometer	VEGA 2	Gradient discussed	Bertaux et al. (), p. 12,737, Table 4
SO2	25 ppm	± 2 ppm	12 km	In situ	UV spectrometer	VEGA 1	Gradient discussed	Bertaux et al. (), p. 12,737, Table 4
SO2	20 ppm	‐	12 km	In situ	UV spectrometer	VEGA 2	Gradient discussed	Bertaux et al. (), p. 12,737, 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. (), 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. (), pp. 390–392, Tables 3and 10
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. (), pp. 390–392, Tables 3 and 10
SO2	*Not detected	‐	23–4 km	In situ	mass spectrometers	Venera 11/12	If present, upper limit < 25 ppm	Istomin et al. (), p. 17
SO	20 ppb	± 10 ppb	cloud top	Remote data	LWP Camera	Intl UV Explorer		Na et al. (), abstract & p. 7490
H2S	3 ppm	± 2 ppm	< 24 km	In situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman, Hodges, Donahue, et al. (), pp. 7789, Table 2
H2S	Not detected*	‐	52–22 km	In situ	LGC	Pioneer Venus	If existent, upper limit < 2 ppm	Oyama et al. (), p.7898, Table 3
H2SO4	8 ppmv	‐	46 km	Remote data	microwave: VLA	Earth based	Rapidly declines below this altitude	Jenkins et al. (), p.324
CH4	Not detected*	‐	22–52 km	Data	LGC	Pioneer Venus	If present, upper limit < 0.6 ppm	Oyama et al. (), 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, (), 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, (), 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. (), Table 4
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. (), Table 4
C2H4	Not detected*	‐	22–52 km	In situ	LGC	Pioneer Venus	If existent, upper limit < 1 ppm	Oyama et al. (), p.7898, Table 3
C2H6	~2 ppm	‐	< 24 km	In situ	LNMS	Pioneer Venus	Deduced from ratio to 36Ar	Hoffman, Hodges, Donahue, et al. (), pp. 7789, Table 2
C2H6	Not detected*	‐	22–52 km	In situ	LGC	Pioneer Venus	If existent, upper limit < 1 ppm	Oyama et al. (), p.7898, Table 3
C3H8	Not detected*	‐	22–52 km	In situ	LGC	Pioneer Venus	If existent, upper limit < 5 ppm	Oyama et al. (), p.7898, Table 3
Cl	< 10 ppm	‐	< 24 km	In situ	LNMS	Pioneer Venus	Upper limit; deduced from measurements.	Hoffman et al. (), p. 50 Hoffman, Hodges, Donahue, et al. (), Table 2
HCl	0.1 ppm	± 0.03 ppm (1σ)	70–75 km	Remote data	SOIR	Venus Express	orbit 136	Bertaux et al. (), p. 648
HCl	0.17 ppm	± 0.03 ppm (1σ)	70–75 km	Remote data	SOIR	Venus Express	orbit 247	Bertaux et al. (), p. 648
HCl	0.4 ppmv	‐	cloud top	Remote data	Fourier Transform Spectrometer	CFHT Earth based	Altitude at 35mbar level	de Bergh et al. (), abstract 6.09‐P
HCl	0.5 ppm	‐	~18 km	Remote data	Fourier Transform Spectrometer	Earth based telescopes	• Used best fit spectrum model	Bézard et al. (), p. 511, Table 1
• Mixing ratio presented as 5 × 10−7
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. (), Table 4
HCl	0.4 ppm	‐	~64 km	model		Value based on chemical modeling and related observations	von Zahn et al. (), pp. 401–403, Table 3
HCl	0.5 ppmv	± 0.15 ppmv	15–30 km	Remote data	IR spectra	Earth based		Bézard (). 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 modeling and related observations	von Zahn et al. (), p. 403, Table 3; Parisot and Moreels (), p. 73
HF	0.001–0.003 ppb	‐	75–85 km	Remote data	SOIR	Venus Express	orbit 114	Bertaux et al. (), p. 648
HF	5 ppbv	± 2 ppbv	30–40 km	Remote data	IR spectra	Earth based		Bézard (). 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. (), Table 4
HF	4.5 ppb 0.0045 ppm	‐	~32 km	Remote data	Fourier transform spectrometer	Earth‐based telescope	• Used best fit spectrum model	Bézard et al. (), p. 510, Table 1
• Mixing ratio presented as 4.5 × 10−9
N2O	*Not detected	‐	22–52 km	In situ	LGC	Pioneer Venus	If present, upper limit < 10 ppm; optimum case	Oyama et al. (), 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, Hodges, Donahue, et al., (), pp. 7789, Table 2

BNMS = Bus Neutral Mass Spectrometer, ONMS = Orbiter Neutral Mass Spectrometer, LNMS = Large probe Neutral Mass Spectrometer, LGC = Large probe Gas Chromatograph.

Isotopic Ratios of the Reactive Gases: Table  Isotopic Ratios of the Reactive Gases

Element	Ratio	Error	Altitude	Technique	Instrument	Mission	Comment	References (with relevant pages and 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. (), p. 630, 633
D/H in H2O	0.019	±0.006	32–42 km	Remote data	Fourier transform spectrometer	Earth‐based telescope	• Venus nightside; 2.34–2.43‐μm window	de Bergh et al. (), p. 548
• CO mixing ratio of 45 ppm at ~42 km
• D/H equal to ½ × [HDO]/[H2O]
D/H	0.025	±0.005	54 km	In situ	Mass spectrometer	Pioneer Venus	Derived from H2SO4 droplets trapped at 54 km	Atreya, personal communication
12C/13C in CO2	86	±12	Cloud tops	Remote data	Michelson interferometer	Earth‐based	Derived from 13CO2 abundance	Bézard et al. (), p. 623 and Table 4
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	Istomin et al. (), p. 13
• Includes contributions from CH+ ions
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, Hodges, Donahue, et al. (), p. 7887 and Table 3
14N/15N	Earth atmospheric 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. (), abstract Value in Lodders and Fegley (), Table 5.5
18O/16O	2.0 × 10−3	±0.1 × 10−3	<24 km	In situ	Mass spectrometer LNMS	Pioneer Venus	Contributions from CO2 and SO2	Hoffman, Hodges, Donahue, et al. (), p. 7888 and Table 3
18O/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. (), p. 623 and Table 5
35Cl/37Cl in HCl	2.9	±0.3	Cloud tops	Remote data	IR spectra	Earth‐based	Primary data presented in Connes et al. (). Calculated from HCl lines in the 2‐0 R‐Branch (Table 1, p. 1231) [value 2.869]	Cited value Young (), p. 640; Connes et al. (), original data

LNMS = Large probe Neutral Mass Spectrometer.

Summary

These tables are by no means the last word on Venus atmospheric data, both measured and modeled, 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.

Acknowledgments

Many thanks are extended to those who preceded this work. Apologies are given to Venus modelers whose work is not included. This compilation would not have come to pass without the encouragement and support of the DAVINCI Principle Investigator Lori Glaze, the DAVINCI Team, and the Astrochemistry Lab Branch/691 at Goddard Space Flight Center. The reviewers were instrumental in clarifying the discussion and provided valuable insight. All the data presented within this manuscript are accessible in the published literature through the cited references.