THE BEAVER-HARRISON,BEAVER COUNTY,UTAH L6 CHONDRITE

The Beaver-Harrison, Utah chondrite (find July 24, 1979), a single, shock-veined stone of 925 grams, consists of major olivine (Fa_25.0), low-Ca pyroxene (En_77.3Fs_21.1Wo_1.6) and metallic nickel-iron; minor troilite and plagioclase (Ab_82.6An_11.1Or_6.3), accessory high-Ca pyroxene (En_47.0Fs_8.5Wo_44.5), chromite (Cm_8.7Sp_10.6Uv_9.4Pc_0.6Hc_0.7), chlorapatite and whitlockite; and hydrous ferric oxide of terrestrial weathering origin. Mineral compositions indicate L-group classification, and homogeneity of minerals, highly recrystallized texture and presence of clear plagioclase suggest that the meteorite belongs to petrologic type 6.     

Near-infrared laboratory spectra of solid H2O/CO2 and CH3OH/CO2 ice mixtures

We present near-IR spectra of solid CO₂ in H₂O and CH₃OH, and find they are significantly different from that of pure solid CO₂. Peaks not present in either pure H₂O or pure CO₂ spectra become evident when the two are mixed. First, the putative theoretically forbidden CO₂ (2ν₃) overtone near 2.134 μm (4685 cm⁻¹), that is absent from our spectrum of pure solid CO₂, is prominent in the spectra of H₂O/CO₂=5 and 25 mixtures. Second, a 2.74-μm (3650 cm⁻¹) dangling OH feature of H₂O (and a potentially related peak at 1.89 μm) appear in the spectra of CO₂-H₂O ice mixtures, but are probably not diagnostic of the presence of CO₂. Other CO₂ peaks display shifts in position and increased width because of intermolecular interactions with H₂O. Warming causes some peak positions and profiles in the spectrum of a H₂O/CO₂=5 mixture to take on the appearance of pure CO₂. Absolute strengths for absorptions of CO₂ in solid H₂O are estimated. Similar results are observed for CO₂ in solid CH₃OH. Since the CO₂ (2ν₃) overtone near 2.134 μm (4685 cm⁻¹) is not present in pure CO₂ but prominent in mixtures, it may be a good observational (spectral) indicator of whether solid CO₂ is a pure material or intimately mixed with other molecules. These observations may be applicable to Mars polar caps as well as outer Solar System bodies.     

ACHONDRITE ALHA77005: ALTERATION OF CHROMITE AND OLIVINE

The olivine crystals of the 77005 achondrite are brown except for colorless shock lamellae, mottled patches, and grains adjacent to pools of impact melt. Sporadic dark alteration patches in brown olivine and Cr-rich spinel gave the following average electron-microprobe analyses: (olivine) P₂O₅ 0.9, SiO₂ 57.9, TiO₂ 0, Al₂O₃ 0.7, Cr₂O₃ 0.4, V₂O₃ 0, Fe₂O₃ (assumed oxidation state) 17.0, MgO 1.6, CaO 0.2, Na₂O 0, K₂O 1.8, SO₃ (assumed oxidation state) 9.2, Cl 0.1, sum 89.8 wt. %; (spinel) P₂O₅3.5, SiO₂2.1, TiO₂.2.2, Al₂O₃2.1, Cr₂O₃ 13.4, V₂O₃ 0.8, Fe₂O₃ 40.7, MgO 0.9, CaO 0.1, Na₂O 0, K₂O 2.0, SO₃ 11.1, Cl 0.1, sum 79.0 wt.%. Ion-microprobe analyses revealed H in both. Rare orange patches in brown olivine from another area gave SiO₂ 33–35, FeO 30-28, MgO 28–32, sum 93 wt. %. Thermal metamorphism under dry oxidizing conditions is discussed as a possible alternative to shock-induced oxidation for generation of the brown olivine (McSween and Stöffler). Because alteration patches transgress shock lamellae, and because sulfatic alteration occurs in fusion crusts of Antarctic meteorites (Gibson et al., 1983), alteration of the 77005 achondrite at the Antarctic surface is preferred to a complex series of processes needed for pre-terrestrial alteration.     

A photo-chemical method for the production of olivine nanoparticles as cosmic dust analogues

This paper describes a new experimental method to synthesise metal silicate particles in the laboratory with compositions and structures which reflect those likely to form in planetary atmospheres and in relatively cool regions of oxygen-rich stellar outflows. Fe–Mg-silicate nanoparticles of olivine composition were produced by the photo-oxidation of a mixture of Fe(CO)₅, Mg(OC₂H₅)₂ and Si(OC₂H₅)₄ vapours in the presence of O₃ at room temperature and atmospheric pressure. Transmission electron microscope X-ray and electron energy loss analysis of the particles from a number of experiments run with different precursor vapour mixture ratios show that Mg_2xFe_2?2xSiO₄ particles can be produced ranging from x = 0 to 1, where x is linearly proportional to the ratio of Mg(OC₂H₅)₂/(Fe(CO)₅ + Mg(OC₂H₅)₂). Electronic structure calculations with hybrid density functional/Hartree–Fock theory are then used to explore the pathways involved in producing olivine particles from the FeO₃, MgO₃ and SiO₂ produced from the photolysis of the organometallic precursors in O₃. These calculations indicate that highly exothermic reactions lead to the formation of Mg₂SiO₄, MgFeSiO₄ and Fe₂SiO₄ molecules, which then polymerize. An alternative pathway, also strongly favoured thermodynamically, is the polymerization of MgSiO₃ and FeSiO₃ to form pyroxenes, which then undergo structural rearrangement to olivine and silica phases. The implications for metal silicate formation in planetary atmosphere and stellar outflows are then discussed.     

Analysis of Cassini/CIRS limb spectra of Titan acquired during the nominal mission: I. Hydrocarbons, nitriles and CO2 vertical mixing ratio profiles

Observations of the Composite InfraRed Spectrometer (CIRS) during the entire nominal Cassini mission (2004-2008) provide us with an accurate global view of composition and temperature in the middle atmosphere of Titan (between 100 and 500 km). We investigated limb spectra acquired at resolution at nine different latitudes between 56°S and 80°N, with a better sampling in the northern hemisphere where molecular abundances and temperature present strong latitudinal variations. From this limb data acquired between February 2005 and May 2008, we retrieved the vertical mixing ratio profiles of C₂H₂, C₂H₄, C₂H₆, C₃H₈, CH₃C₂H, C₄H₂, C₆H₆, HCN, HC₃N and CO₂. We present here for the first time, the latitudinal variations of the C₂H₆, C₃H₈, CO₂, C₂H₄ and C₆H₆ vertical mixing ratios profiles. Some molecules, such as C₂H₆ or C₃H₈ present little variations above their condensation level. The other molecules (except CO₂) show a significant enhancement of their mixing ratios poleward of 50°N. C₂H₄ is the only molecule whose mixing ratio decreases with height at latitudes below 46°N. Regions depleted in C₂H₂, HCN and C₄H₂ are observed around 400 km (0.01 mbar) and 55°N. We also inferred a region enriched in CO₂ located between 30 and 40°N in the 2-0.7 mbar pressure range. At 80°N, almost all molecules studied here present a local minimum of their mixing ratio profiles near 300 km (∼0.07 mbar), which is in contradiction with Global Circulation Models that predict constant-with-height vertical profiles due to subsidence at the north pole.     

Sulfurous acid (H2SO3) on Io?

Sulfurous acid (H₂SO₃) has never been characterized or isolated on Earth. This is caused by the unfavorable conditions for H₂SO₃ within Earth's atmosphere due to the high temperatures, the high water content and the oxidizing environment. Kinetic investigations by means of transition state theory showed that the half-life of H₂SO₃ at 300 K is 1 day but at 100 K it is increased to 2.7 billion years. Natural conditions to form H₂SO₃ presumably require cryogenic SO₂ or SO₂/H₂O mixtures and high energy proton irradiation at temperatures around 100 K. Such conditions can be found on the Jupiter moons Io and Europa. Therefore, we calculated IR-spectra of H₂SO₃ which we compared with Galileo's spectra of Io and Europa. From the available data we surmise that H₂SO₃ is present on Io and probably but to a smaller extent on Europa.     

The clouds of Venus: Sulfuric acid by the lead chamber process

The Pioneer Venus atmospheric probe provided new data on the louds of Venus. A model consistent with this data involves SO₂ being oxidized to H₂SO₄ by NO_x in the presence of H₂O. NO_x also forms nitrosylsulfuric acid (NOHSO₄) dissolved in the H₂SO₄ droplets. This acid solution, along with SO₂ and perhaps NO₂, can explain the uv and visible reflection spectrum of Venus. In the middle and lower clouds NOHSO₄ forms solid particles.     

Perturbation equations of the elements of Vinti's intermediate orbit

Perturbation equations of the elements a, e, s, M_s, Ψ_s,Ω_sof Vinti's intermediate orbit are derived here correct to the second-order. Poisson terms have been eliminated from these equations.     

Mass spectrometric measurements of fractional ion abundances in the stratosphere—Negative ions

Fractional abundances of stratospheric negative ions are for the first time explicitly reported. The measurements made by balloon-borne ion mass spectrometers also rely on recent studies of electric field induced collisional dissociation of negative cluster ions conducted at our laboratory. These indicate that the negative ion composition measurements around 36 km conducted by our group do not suffer from any significant dissociation. The new composition data support ion identifications NO₃^?(HNO₃)_b and HSO₄^?(H₂SO₄)_c(HNO₃)_d and the underlying ion reactions propo previously. Moreover, it is found that HSO₄^?(H₂SO₄)_g-ions appear to be particularly stable and that H₂SO₄-association is very fast. Implications of the ion composition data for ion processes are discussed.     

Infrared polar brightening on Jupiter: III. Spectrometry from the Voyager 1 IRIS experiment

Spectra from the Voyager 1 IRIS experiment confirm the existence of enhanced infrared emission near Jupiter's north magnetic pole in March 1979. The spectral characteristics of the enhanced emission are consistent with a Planck source function. A temperature-pressure profile is derived for the region near the north magnetic pole, from which quantitative abundance estimates of minor species are made. Some species previously detected on Jupiter, including CH₃D, C₂H₂ and C₂H₆, have been observed again near the pole. Newly discovered species, not previously observed on Jupiter, include C₂H₄, C₃H₄, and C₆H₆. All of these species except CH₃D appear to have enhanced abundances at the north polar region with respect to midlatitudes. Upper limits are determined for C₄H₂ and C₃H₈. The quantitative results are compared with model calculations based on ultraviolet results from the IUE satellite. The plausibility of the C₆H₆ identification in discussed in terms of the literature on C₂H₂ polymerization. The relation of C₆H₆ to cuprene is also discussed.     

Radiolysis of sulfuric acid, sulfuric acid monohydrate, and sulfuric acid tetrahydrate and its relevance to Europa

We report laboratory studies on the 0.8 MeV proton irradiation of ices composed of sulfuric acid (H₂SO₄), sulfuric acid monohydrate (H₂SO₄·H₂O), and sulfuric acid tetrahydrate (H₂SO₄·4H₂O) between 10 and 180 K. Using infrared spectroscopy, we identify the main radiation products as H₂O, SO₂, (S₂O₃)_x, H₃O⁺, , and . At high radiation doses, we find that H₂SO₄ molecules are destroyed completely and that H₂SO₄·H₂O is formed on subsequent warming. This hydrate is significantly more stable to radiolytic destruction than pure H₂SO₄, falling to an equilibrium relative abundance of 50% of its original value on prolonged irradiation. Unlike either pure H₂SO₄ or H₂SO₄·H₂O, the loss of H₂SO₄·4H₂O exhibits a strong temperature dependence, as the tetrahydrate is essentially unchanged at the highest irradiation temperatures and completely destroyed at the lowest ones, which we speculate is due to a combination of radiolytic destruction and amorphization. Furthermore, at the lower temperatures it is clear that irradiation causes the tetrahydrate spectrum to transition to one that closely resembles the monohydrate spectrum. Extrapolating our results to Europa’s surface, we speculate that the variations in SO₂ concentrations observed in the chaotic terrains are a result of radiation processing of lower hydration states of sulfuric acid and that the monohydrate will remain stable on the surface over geological times, while the tetrahydrate will remain stable in the warmer regions but be destroyed in the colder regions, unless it can be reformed by other processes, such as thermal reactions induced by diurnal cycling.     

Laboratory simulations of PH3 photolysis in the atmospheres of Jupiter and Saturn

Photolysis of NH₃PH₃ mixtures (11 Torr) at 175°K resulted in the same initial rate of P₂H₄ formation as when the 11 Torr of pure PH₃ was photolyzed. A higher yield of P₂H₄ is obtained at 175°K than at 298°K because some of the P₂H₄ condenses on the cell wall at 175°K and is not subject to further reaction. Some reaction of P₂H₄ is taking place as observed by the decrease in its yield and on the formation of red phosphorus on extended photolysis of PH₃ at 175°K. No NH₂PH₂ or (PN)_x were detected as photoproducts as indicated by the absence of change in the UV spectral properties of the P₂H₄ and red phosphorus fraction, respectively, when NH₃ is present. Although the pathway for PH₃ decomposition is changed, the outcome of the photochemical process is essentially the same in the absence or presence of NH₃. The formation of P₂H₄ and red phosphorus was not inhibited by small amounts of C₂H₄ and C₂H₂, so the low levels of hydrocarbons on Jupiter and Saturn will not have a significant effect on the course of PH₃ photolysis. The ratio of products of PH₃ photolysis are only slightly affected by the wavelength of light used. Use of xenon lamp, with a continuous emission in the ultraviolet where P₂H₄ absorbs, results in only a modest decrease in the yield of P₂H₄ and a modest increase in the rate of formation of red phosphorus as compared to the rates observed with a 206.2-nm light source. The quantum yield for P₂H₄ formation is pressure independent in the 0.5–11 Torr range. This quantum yield is not affected by lowering the temperature to 157°K or by the addition of 100 Torr of H₂. It is concluded that photolysis of PH₃ to P₂H₄ and the subsequent conversion of P₂H₄ to red phosphorus are likely procses on Jupiter and Saturn and that particles of P₂H₄ condense in the atmospheres of these planets. The conversion of some of the P₂H₄ to red phosphorus may take place on Jupiter.     

Formation and photochemistry of Methylamine in Jupiter's atmosphere

The formation of methylamine (CH₃NH₂) in the upper troposphere and lower stratosphere of Jupiter is investigated. Translationally hot hydrogen atoms are produced in the photolysis of ammonia, phosphine, and acetylene which react with methane to produce methyl (CH₃) radicals; the latter recombine with NH₂ to form CH₃NH₂. Also, methane is catalytically dissociated to CH₃ + H by the species C₂ and C₂H produced in the photolysis of acetylene. It is shown that the combined production of CH₃NH₂ and subsequent photolysis to HCN is unlikely to account for the HCN observed near Jupiter's tropopause. Recombination of NH₂ and C₂H₅N followed by photolysis to HCN is the preferred path. Production of C₂H₆ by these two processes is negligible in comparison to the downward flux of C₂H₆ from the Lyman α photolysis region of CH₄. An upper limit column density on CH₃PH₂ is estimated to be ～10¹³ cm^?2 as compared to 10¹⁵ cm^?2 for CH₃NH₂. Hot H atoms account for a negligible fraction of the total ortho-para conversion by the reaction H + H₂     

Stratospheric in situ measurements of H2SO4 and HSO3 vapors during a volcanically active period

In situ measurements of stratospheric H₂SO₄ and HSO₃vapors using passive chemical ionization mass spectrometry were made in October 1982 after the eruption of volcano El Chichon. Data were obtained between about 20 and 41 km showing [H₂SO₄ + HSO₃] sum concentrations between about 10⁴ and 2 × 10⁵ cm^?3 below 29 km and a steep rise above this altitude. Maximum [H₂SO₄ + HSO₃] values of about 3 × 10⁶ cm^?3 are reached above 35 km.Partial [HSO₃] concentrations increase above 34 km reaching about $\text{4 × 10}{}^5\text{cm}{}^{\mathrm{?3}}$ around 40 km. From the measurements it is concluded that H₂SO₄ and probably HSO₃photolysis have an important influence above 34 km leading to the observed increase of [HSO₃] and a depletion of H₂SO₄vapor.It also seems that the data support the view of heterogeneous HSO₃ removal. If correct, this would imply that stratospheric aerosols are formed primarily from HSO₃ rather than H₂SO₄vapor.     

Identification of C4H5, C4H4, C3H3 and CH3 radicals produced from the reaction of atomic carbon with propene: Implications for the atmospheres of Titan and giant planets and for the interstellar medium

We observed the products C₄H₅, C₄H₄, C₃H₃ and CH₃ of the C(³P) + C₃H₆ reaction using product time-of-flight spectroscopy and selective photoionization. The identified species arise from the product channels C₄H₅ + H, C₄H₄ + 2H and C₃H₃ + CH₃. Product isomers were identified via measurements of photoionization spectra and calculations of adiabatic ionization energy. Product C₄H₅ probably involves three isomers HCCCHCH₃, H₂CCCCH₃ and H₂CCCHCH₂. In contrast, products C₄H₄ and C₃H₃ involve exclusively HCCCHCH₂ and H₂CCCH, respectively. Reaction mechanisms are unraveled with crossed-beam experiments and quantum-chemical calculations. The ³P carbon atom attacks the π orbital of propene (C₃H₆) to form a cyclic complex c-H₂C(C)CHCH₃ that rapidly opens the ring to form H₂CCCHCH₃ followed by decomposition to HCCCHCH₃/H₂CCCCH₃/H₂CCCHCH₂ + H and H₂CCCH + CH₃; the corresponding branching ratios are 7:5:10:78 predicted with RRKM calculations at collision energy 4 kcal mol^?1. Nascent C₄H₅ with enough internal energy further decomposes to HCCCHCH₂ + H. Ratios of products C₄H₅, C₄H₄ and C₃H₃ are experimentally evaluated to be 17:8:75. This work provides a comprehensive look at product channels of the title reaction and gives implications for the formation of hydrocarbons in extra-terrestrial environments such as Titan and carbon-rich interstellar media. We suggest that the title reaction, hitherto excluded in any chemical networks, needs to be taken into account at least in the atmosphere of Titan and carbon-rich molecular clouds where rapid neutral–neutral reactions are dominant and carbon atoms and propene are abundant.     

Experimental impact shock chemistry on planetary icy satellites

We present new experimental results on impact shock chemistry into icy satellites of the outer planets. Icy mixtures of pure water ice with CO₂, Na₂CO₃, CH₃OH, and CH₃OH/(NH₄)₂SO₄ at 77 K were ablated with a powerful pulsed laser—a new technique used to simulate shock processes which can occur during impacts. New products were identified by GC-MS and FTIR analyses after laser ablation. Our results show that hydrogen peroxide is formed in irradiated H₂O/CO₂ ices with a final concentration of 0.23%. CO and CH₃OH were also detected as main products. The laser ablation of frozen H₂O/Na₂CO₃ generates only CO and CO₂ as destruction products from the salt. Pulsed irradiation of water ice containing methanol leads also to the formation of CO and CO₂, generates methane and more complex molecules containing carbonyl groups like acetaldehyde, acetone, methyl formate, and a diether, dimethyl formal. The last three compounds are also produced when adding ammonium sulfate to H₂O/CH₃OH ice, but acetone is more abundant. The formation of two hydrocarbons, CH₄ and C₂H₆ is observed as well as the production of three nitrogen compounds, nitrous oxide, hydrogen cyanide, and acetonitrile.     

SHERGOTTY METEORITE: MINERALOGY,PETROGRAPHY AND MINOR ELEMENTS

The unusual achondrite Shergotty resembles terrestrial diabases, and textural and chemical evidence indicates pre-settling and post-settling crystallization of zoned augite (En₄₈Fs₁₉Wo₃₃-En₂₅Fs₄₇Wo₂₈) and pigeonite (En₆₁Fs₂₆Wo₁₃-En₂₁Fs₆₁Wo₁₈) coupled with late crystallization of plagioclase (Ab₄₃An₅₆/Or₁-Ab₅₆An₄₁Or₃: now shocked to maskelynite), titanomagnetite-ilmenite composite grains, mesostasis (normative Qz₃₄Ab₂₁An₅Or₃₈Fs₂, assuming Fe as ferrous), whitlockite, pyrrhotite (Fe_0.94S), fayalite (Fo₁₀), baddeleyite and chlorapatite. The oxide compositions (Usp₆₂Mt₃₈, Al₂O₃ 2.4, Cr₂O₃ 0.8 wt %; Ilm₉₅Hm₅) indicate ～ 850 °C and log oxygen fugacity ? 14, while the occurrence of fayalite rims on mesostasis next to ilmenite indicates 890 °C. Bearing in mind experimental uncertainties, these data are consistent with late-stage crystallization under relatively high oxygen fugacity, as indicated by coexistence of fayalite, Ti-magnetite and a silica glass. The high alkali content of the maskelynite and mesostasis, coupled with the redox state, indicates that the Shergotty meteorite resembles terrestrial basalts more than any other meteorites. Nevertheless the absence of H₂O, as shown by the occurrence of phosphorus in whitlockite rather than in hydroxylapatite, distinguish the Shergotty achondrite from typical terrestrial diabases. Whereas the FeO/MnO ratios of pyroxenes from the Moon, Earth and several differentiated meteorites are independent of FeO, the ratio for Shergotty pyroxenes changes from 30 to 40 with increasing FeO, and the linear trend extrapolates to 0.2 MnO for zero iron. Hence caution is needed in using FeO/MnO as a planetary indicator. For pyroxenes, Na is almost independent of Fe/Mg while Ti increases and Cr decreases with increasing Fe/Mg. Maskelynite contains 0.5–0.25 wt % K₂O, 0.6 wt % FeO, 0.04 TiO₂, 0.04–0.07 MgO, ～ 0.01 BaO and 0.02–0.03 P₂O₅. A bulk analysis calculated from the mode and compositions of the minerals matches quite well with two bulk chemical analyses but not with a third.     

Global atmospheric monitoring with SCIAMACHY

SCIAMACHY (SCanning Imaging Absorption spectrometer for Atmospheric CHartographY) is a space based spectrometer designed to measure sunlight transmitted, reflected and scattered by the Earth atmosphere or surface. It is a contribution to the Envisat-1 satellite to be launched in late 1999.SCIAMACHY measurements will provide amounts and distribution of 0₃, BrO, OCl0, ClO, S0₂, H₂CO, N0₂, CO, CO₂, CH₄, H₂O, N₂0, pressure, temperature, aerosol, radiation, cloud cover and cloud top height from atmospheric measurements in nadir, limb and occultation geometry.By the combination of the near simultaneous limb and nadir observations SCIAMACHY is one of a limited number of instruments which is able to detect tropospheric column amounts of 0₃, N0₂, CO, CH₄, H₂O, N₂0, S0₂, H₂CO, and BrO down to the planetary boundary layer under cloud free conditions.     

Integrability of the Yang-Mills Hamiltonian system

This paper considers the integrability of generalized Yang-Mills system with the HamiltonianH _a (p, q)=1/2(p ₁ ² +p ₂ ² +a ₁ q ₁ ² +a ₂ q ₂ ² )+1/4q ₁ ⁴ +1/4a ₃ q ₂ ⁴ + 1/2a ₄ q ₁ ² q ₂ ² . We prove that the system is integrable for the cases: (A)a ₁=a ₂,a ₃=a ₄=1; (b)a ₁=a ₂,a ₃=1,a ₄=3; (C)a ₁=a ₂/4,a ₃=16,a ₄=6. Our main result is the presentation of these integrals. Only for cases A and B does the Yang-Mills Hamiltonian possess the Painlevé property. Therefore the Painlevé test does not take account of the integrability for the case C.     

The composition of the Martian atmosphere: Minor constituents

The Mariner 6 and 7 infrared spectrometers provided data which, in principle, determine upper limits on the possible atmospheric abundance of every gaseous substance that was undetected but which has recognized absorptions in the accessible spectral region, 1.9 to 14.4 μ. Through supporting laboratory determinations of curves of growth under pressure broadening conditions appropriate to Mars, upper limits can be specified (expressed first in cm-atm, STP, for a vertical column and then in parts per million) for the following gases: NO₂ (<0.0016, 0.23); NH₃ (<0.0031, 0.44); C₃O₂ (<0.0032, 0.45); SO₂ (?0.0037, 0.52); OCS (<0.0040, 0.56); NO (<0.0050, 0.70); O₃ (<0.0061, 0.86); CH₄ (<0.026, 3.7); N₂O (<0.13, 18); HCl (<3.7, 520); HBr (?8.2, 1150); H₂S (<27, 3800). In addition, considerations of band contours, moments of inertia, and experimental absorption coefficients permit us to place useful upper limits on twenty-seven additional substances that were not detected and for which curves of growth have not been measured: less than 1.0ppm (or, <0.0071cm-atm); SF₆, NF₃, Cl₂CO, CF₄, CHF₃, Br₂CO, SiF₄; less than 6.0ppm (or, <0.035 cm-atm); C₂F₆, CO₃, F₂CO, C₂H₄, BF₃, CS₂, CHCl₃, C₂H₆, H₂CO, CH₃F, C₆H₆, CH₂I₂; less than 50ppm (or, <0.35 cm-atm): C₂H₂, HCN, CH₂Br₂, CH₂Cl₂, CH₃Br, PH₃, CH₃I, and CH₃Cl. These upper limits are compared to earlier limits based upon terrestrial measurements. The present limits placed upon the possible atmospheric content of the molecules C₃O₂ and CO₃ are of particular interest because of their relevance to the photochemistry of the Martian atmosphere.