J. P. Maillard

Deuterium on Venus: Observations From Earth

Absorption lines of HDO and H2O have been detected in a 0.23-wave number resolution spectrum of the dark side of Venus in the interval 2.34 to 2.43 micrometers, where the atmosphere is sounded in the altitude range from 32 to 42 kilometers (8 to 3 bars). The resulting value of the deuterium-to-hydrogen ratio (D/H) is 120 � 40 times the telluric ratio, providing unequivocal confirmation of in situ Pioneer Venus mass spectrometer measurements that were in apparent conflict with an upper limit set from International Ultraviolet Explorer spectra. The 100-fold enrichment of the D/H ratio on Venus compared to Earth is thus a fundamental constraint on models for its atmospheric evolution.

Ground‐based near‐infrared observations of the Venus nightside: 1.27‐μm O2(a 1Δ g ) airglow from the upper atmosphere

Near-infrared spectroscopic observations of Venus taken in 1975 revealed O2(a1Δg) airglow from both the dayside and nightside of the planet with emission rates exceeding 1 mega-Rayleigh (1 MR = 1012 photons cm−2 s−1 into 4π sr). These large emission rates indicated that most of the atomic oxygen produced through the photolysis of CO2 on the dayside of Venus eventually recombined to produce O2 in the excited (a1Δg) state. This result was initially surprising because available laboratory measurements indicated O2(a1Δg) yields from atomic oxygen recombination reactions that were no larger than a few percent. More recent observations reveal even larger O2(a1Δg) airglow intensities as well as dramatic spatial and temporal variations in this airglow. High-resolution (0.3 cm−1) spectra of the Venus nightside taken with the Canada France Hawaii Telescope/Fourier transform spectrometer in 1991 show spectrally integrated O2(a1Δg) intensities as large as 1.1 mW m−2 sr−1. Once these values are corrected for viewing angle and reflection from the underlying clouds, they indicate emission rates near 3 MR. These spectra also yield rotational temperatures of 186 ± 6 K in the emitting layer (90 to 115 km). Spectral image cubes taken with the Anglo-Australian Telescope/infrared imaging spectrometer and the Canada France Hawaii Telescope/imaging Fourier transform spectrometer during 1991, 1993, and 1994 provide a more complete description of the spatial and temporal variability in this emission. Images extracted at wavelengths within the O2(a1Δg) Q-branch (1.269 μm) often show contrasts larger than 10 to 1 across the nightside. Even though the disk-averaged intensities are comparable to those seen in 1975, some localized regions have airglow emission rates larger than 5 MR. The brightest emission is often confined to 1000- to 2000-km-diameter regions. These bright regions have been detected over a broad range of latitudes and local times, but they are most often seen at low latitudes and at local times between midnight and 0300 on Venus. The intensity of the brightest spots can change by 20% in less than 1 hour, and they can vanish entirely in less than 1 day. These new observations are providing improved constraints on atmospheric chemical and dynamical models of the upper mesosphere and lower thermosphere of Venus.

Hot and cold gas toward young stellar objects

High-resolution M band spectra are presented for the seven embedded IR sources W3 IRS 5, S140 IRS1, NGC 7538 IRS 1, NGC 7538 IRS 9, GL 2136, LkH-alpha 101, and MWC 349A, and the data are combined with previously published work for W33A and GL 2591. Cold CO is seen toward all nine sources, with temperatures from 11 K to 66 K. Column densities of cold CO are presented. Hot gas is seen toward eight of the nine objects with temperatures from 120 K to 1010 K. New lower limits to the hot gas density are obtained. The hot gas toward GL 2591, GL 2136, W3 IRS 5, and S140 IRS 1 is probably very near the central source and heated via gas-grain collisions. The optical depth in the silicate feature is strongly correlated with the (C-13)O column density, confirming that silicate optical depth is a useful measure of gas column density. The ratio of solid-to-gaseous CO is obtained for seven sources. 43 refs.

WATER IN THE DEEP ATMOSPHERE OF VENUS FROM HIGH-RESOLUTION SPECTRA OF THE NIGHT SIDE

High-resolution, near-infrared (1.09 to 2.5 μm) spectra of the night side of Venus have been obtained in 1990 and 1991 using the Fourier Transform Spectrometer at the 3.6-m Canada-France-Hawaii telescope. Absorptions due to H2O were detected in spectral windows near 2.3, 1.74, and 1.18 μm. Our analysis of these absorptions constrains the abundance of water vapor in three different altitude ranges located between the clouds and the surface: 30–40 km, 15–25 km and 0–15 km. A constant water vapor mixing ratio of 30±15 ppm below the clouds can fit the observations. These values are consistent with recent near-infrared studies of the night side of Venus at lower spectral resolution. The atmosphere of Venus appears to be dryer than originally suggested by the in-situ measurements made by the Pioneer Venus and Venera mass-spectrometers and gas-chromatographs.

The abundance of sulfur dioxide below the clouds of Venus

We present a new method for determining the abundance of sulfur dioxide below the clouds of Venus. Absorption by the 3ν3 band of SO2 near 2.45 µm has been detected in high-resolution spectra of the night side of Venus recorded at the Canada-France-Hawaii telescope in 1989 and 1991. The inferred SO2 abundance is 130±40 ppm at all observed locations and pertains to the 35–45 km region. These values are comparable to those measured by the Pioneer Venus and Venera 11/12 entry probes in 1978. This stability stands in contrast to the apparent massive decrease in SO2 observed at the cloud tops since these space missions. These results are consistent with laboratory and modelling studies of the SO2 destruction rates in the lower atmosphere of Venus. The new spectroscopic technique presented here allows a remote monitoring of the SO2 abundance below the clouds, a likely tracer of Venusian volcanism.

H3(+) fundamental band in Jupiter's auroral zones at high resolution from 2400 to 2900 inverse centimeters

Following the previous detection of H3(+) in the southern auroral zone of Jupiter from its 2nu2 band, a search was made for the fundamental at 4 microns. Up to 42 lines of this band were detected in emission, at high resolution, on the auroral spot of each hemisphere. A rotational temperature was derived for the southern and northern zones, respectively, of 1000 + or - 40K and 835 + or - 50 K. The intensity of the lines was on the average two times stronger in the south than in the north. The 2nu2 band, which was sought in the north only on this occasion, was not detectable. A purely thermal mechanism for the H3(+) production is implied. Spatial extension and temporal variability of the excitation is discussed. 20 refs.

The region of the 3ν3 band of methane

Abstract The spectrum of methane near 9000 cm −1 , the region of the 3 ν 3 band, has been recorded at Meudon Observatory with a Fourier transform spectrometer under high resolution. Intensity measurements at two different temperatures, 149 and 295 K, have allowed us to identify two new vibration bands by determining the lower-state quantum numbers J of the transitions. About 100 lines are now assigned in this range, including P and Q branches. Furthermore, the first detailed rotational analysis of the 3 ν 3 band has been made; nine parameters of the band have been determined. The standard deviation of the differences between observed and computed wavenumbers for 45 lines of the 3 ν 3 band is only 0.045 cm −1 . It is found that the observed 45 lines of the 3 ν 3 band correspond to the sublevel l 3 = 3 and C v = F 2 .

Temperatures of the Jovian auroral zone inferred from 2-μm H2 quadropole line observations

Abstract We have observed 2-μm H 2 quadropole lines, S 1 (0), S 1 (1), and S 1 (2), in the southern auroral zone of Jupiter. From the observed intensities, we derived a rotational temperature of 730°K plus 490°K and minus 200°K in the 1 to 0.01 μbar pressure range. We conclude that the derived rotational temperature should represent the local neutral kinetic temperature. Furthermore, we found that H 2 ( ν = 1) population in the auroral zone is at least 500 times greater than the normal Boltzmann population, indicating that nonthermal emission is dominant for these lines. We also calculated both nonthermal and thermal intensities of the pure H 2 rotational quadropole lines and found the opposite result—that the thermal emission dominates over the nonthermal emission—for those lines in the longer wavelength region (>5 μ m).

Episodic outflows from high-mass protostars

This paper examines the kinematics and physical properties of the outflowing gas from seven luminous deeply embedded young stellar objects or protostars: M8E-IR, GL 490, GL 2591, W3 IRS 5, NGC 7538 IRS 1, NGC 7538 IRS 9, and S140 IRS 1. The outflows are seen as blueshifted absorption features in lines of the fundamental band of CO. The CO lines seen in absorption are compared with CO lines seen in emission at mm wavelengths. New CO J = 2-1 emission-line data are presented for the first five of the sources. 60 refs.

Jupiter: Evidence for a Phosphine Enhancement at high Northern latitudes

Abstract High-resolution observations of the Q branch of the 2 ν 2 band of phosphine at 1972 cm −1 on Jupiter show an enhancement of the PH 3 concentration in the deep troposphere ( p ⩾1 bar) by about 60% at high Northern (∼50°N) latitudes compared to both the North Equatorial Belt and the Great Red Spot. Difference in photochemistry or in deep vertical diffusion of PH 3 could be involved to interpret such variations.