238 research outputs found
Temporal behavior of the SO 1.707 micron ro-vibronic emission band in Io's atmosphere
We report observations of the ro-vibronic transition of SO at 1.707 microns
on Io. These data were taken while Io was eclipsed by Jupiter, on four nights
between July 2000 and March 2003. We analyze these results in conjunction with
a previously published night to investigate the temporal behavior of these
emissions. The observations were all conducted using the near-infrared
spectrometer NIRSPEC on the W.M. Keck II telescope. The integrated emitted
intensity for this band varies from 0.8 x 10^27 to 2.4 x 10^27 photons/sec,
with a possible link to variations in Loki's infrared brightness. The
band-shapes imply rotational temperatures of 550-1000K for the emitting gas,
lending further evidence to a volcanic origin for sulfur monoxide. An attempt
to detect the ro-vibronic transition of SO at 0.97 microns was unsuccessful;
simultaneous detection with the 1.707 micron band would permit determination of
the SO column abundance.Comment: 10 pages 4 figures. Accepted by Icarus 02/27/200
Aggregate Hazes in Exoplanet Atmospheres
Photochemical hazes have been frequently used to interpret exoplanet
transmission spectra that show an upward slope towards shorter wavelengths and
weak molecular features. While previous studies have only considered spherical
haze particles, photochemical hazes composed of hydrocarbon aggregate particles
are common throughout the solar system. We use an aerosol microphysics model to
investigate the effect of aggregate photochemical haze particles on
transmission spectra of warm exoplanets. We find that the wavelength dependence
of the optical depth of aggregate particle hazes is flatter than for spheres
since aggregates grow to larger radii. As a result, while spherical haze
opacity displays a scattering slope towards shorter wavelengths, aggregate haze
opacity can be gray in the optical and NIR, similar to those assumed for
condensate cloud decks. We further find that haze opacity increases with
increasing production rate, decreasing eddy diffusivity, and increasing monomer
size, though the magnitude of the latter effect is dependent on production rate
and the atmospheric pressure levels probed. We generate synthetic exoplanet
transmission spectra to investigate the effect of these hazes on spectral
features. For high haze opacity cases, aggregate hazes lead to flat, nearly
featureless spectra, while spherical hazes produce sloped spectra with clear
spectral features at long wavelengths. Finally, we generate synthetic
transmission spectra of GJ 1214b for aggregate and spherical hazes and compare
them to space-based observations. We find that aggregate hazes can reproduce
the data significantly better than spherical hazes, assuming a production rate
limited by delivery of methane to the upper atmosphere.Comment: 17 figures, accepted to Ap
Ammonia Abundance Derived from Juno MWR and VLA Observations of Jupiter
The vertical distribution of trace gases in planetary atmospheres can be
obtained with observations of the atmosphere's thermal emission. Inverting
radio observations to recover the atmospheric structure, however, is
non-trivial, and the solutions are degenerate. We propose a modeling framework
to prescribe a vertical distribution of trace gases that combines a
thermo-chemical equilibrium model {based on a vertical temperature structure
and compare these results to models where ammonia can vary between pre-defined
pressure nodes}. To this means we retrieve nadir brightness temperatures and
limb-darkening parameters, together with their uncertainties, from the Juno
Microwave Radiometer (MWR). We then apply this framework to MWR observations
during Juno's first year of operation (Perijove passes 1 - 12) and to
longitudinally-averaged latitude scans taken with the upgraded Very Large Array
(VLA) (de Pater 2016,2019a). We use the model to constrain the distribution of
ammonia between -60 and 60 latitude and down to 100 bar. We
constrain the ammonia abundance to be ppm
( solar abundance), and find a depletion of
ammonia down to a depth of 20 bar, which supports the existence of
processes that deplete the atmosphere below the ammonia and water cloud layers.
At the equator we find an increase of ammonia with altitude, while the zones
and belts in the mid-latitudes can be traced down to levels where the
atmosphere is well-mixed. The latitudinal variation in the ammonia abundance
appears to be opposite to that shown at higher altitudes, which supports the
existence of a stacked-cell circulation model.Comment: Accepted by Planetary Science Journa
High Spatial and Spectral Resolution Observations of the Forbidden 1.707 ÎŒm Rovibronic SO Emissions on Io: Evidence for Widespread Stealth Volcanism
We present observations obtained with the 10 m Keck telescopes of the forbidden SO aÂčÎ â X³Σ⻠rovibronic transition at 1.707 ÎŒm on Io while in eclipse. We show its spatial distribution at a resolution of ~0.â12 and a spectral resolution of R ~ 2500, as well as disk-integrated spectra at a high spectral resolution (R ~ 15,000). Both the spatial distribution and the spectral shape of the SO emission band vary considerably across Io and over time. In some cases the SO emissions either in the core or the wings of the emission band can be identified with volcanoes, but the largest areas of SO emissions usually do not coincide with known volcanoes. We suggest that the emissions are caused by a large number of stealth plumes, produced through the interaction of silicate melts with superheated SOâ vapor at depth. The spectra, in particular the elevated wing of the emission band near 1.69 ÎŒm, and their spatial distribution strongly suggest the presence of nonlocal thermodynamic equilibrium processes in addition to the direct ejection of excited SO from the (stealth and other) volcanic vents
Neptune's deep atmosphere revealed
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/94842/1/grl4440.pd
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