Aims: In spite of considerable progress in the last two decades, Io's atmosphere remains poorly understood. The goal of this work is to improve our understanding of its spatial distribution, ...temperature and dynamics. Methods: We present millimeter observations of Io's surface and SO2 atmosphere at 1.4 mm obtained with the IRAM Plateau de Bure Interferometer in January-February 2005. With a synthesized beam of 0.5×1.5'', these observations resolve Io's ~1.0'' disk in the longitudinal / local time direction, and sample the leading and trailing hemispheres of Io. Results: The measured continuum total flux and visibilities show that continuum radiation originates from a depth of at least 1 cm in Io's subsurface. On both the leading and trailing sides, emission in the SO2 216.643 GHz line appears spatially narrower than the continuum, and suggests that the atmosphere covers ~80% of the surface on the leading side and ~60% on the trailing. On the leading side, disk-resolved spectra yield Doppler shift measurements, indicating a beam-integrated limb-to-limb velocity difference of 330 ± 100 m/s in the prograde direction. Such a flow allows an improved fit of disk-averaged SO2 spectra, but its origin remains to be understood. Mean gas temperatures are in the range 130-180 K, in agreement with estimates from IR measurements, and with a tendency for higher trailing vs leading side gas temperatures. On the basis of realistic plume models, we find that the contribution of isolated volcanic plumes to the SO2 emission is small.
We present the latest results of the Meudon Multicolor Survey. This survey is aimed at characterizing the color properties and trends of Centaurs and trans-Neptunian objects. We report IJHK ...photometry of objects obtained with CFHT-IR at the 3.6 m Canada-France-Hawaii Telescope (Hawaii), JHK photometry with INGRID at the 4.2 m William Hershel Telescope (La Palma), and BVRI photometry with OIG at the 3.6 m Telescopio Nazionale Galileo Telescope (La Palma). We present visible---near-IR colors for 38 objects. Either these were acquired simultaneously, or the new near-IR photometry was tied to previously published visible measurements using the I magnitude measured in both sets. This large sample allows an extended characterization of the color properties of these primitive objects over the B (0.4 mum) to K (2.2 mum) wavelength range. We performed a detailed statistical analysis of all available IR colors in order to search for significant trends. The most relevant conclusion about visible and near-IR color-color correlations is that, basically, JHK bands alone do not show evidence of correlations, either between them or with BVRIJ bands. Only Centaurs show an anticorrelation between visible colors and H - K. Colors within each dynamical family compare very similarly.
Planet. Sci. J. 4 142 (2023) We present a thermal observation of Callisto's leading hemisphere obtained
using the Atacama Large Millimeter/submillimeter Array (ALMA) at 0.87 mm (343
GHz). The angular ...resolution achieved for this observation was
$\sim$$0.16^{\prime\prime}$, which for Callisto at the time of this observation
($D\sim 1.05^{\prime\prime}$) was equivalent to $\sim$6 elements across the
surface. Our disk-integrated brightness temperature of 116 $\pm$ 5 K (8.03
$\pm$ 0.40 Jy) is consistent with prior disk-integrated observations. Global
surface properties were derived from the observation using a thermophysical
model (de Kleer et al. 2021) constrained by spacecraft data. We find that
models parameterized by two thermal inertia components more accurately fit the
data than single thermal inertia models. Our best-fit global parameters adopt a
lower thermal inertia of 15-50
$\text{J}\:\text{m}^{-2}\:\text{K}^{-1}\:\text{s}^{-1/2}$ and a higher thermal
inertia component of 1200-2000
$\text{J}\:\text{m}^{-2}\:\text{K}^{-1}\:\text{s}^{-1/2}$, with retrieved
millimeter emissivities of 0.89-0.91. We identify several thermally anomalous
regions, including spots $\sim$3 K colder than model predictions co-located
with the Valhalla impact basin and a complex of craters in the southern
hemisphere; this indicates the presence of materials possessing either a higher
thermal inertia or a lower emissivity. A warm region confined to the
mid-latitudes in these leading hemisphere data may be indicative of regolith
property changes due to exogenic sculpting.
NaCl & KCl in Io's Atmosphere Redwing, Erin; de Pater, Imke; Luszcz-Cook, Statia ...
arXiv.org,
09/2022
Paper, Journal Article
Odprti dostop
We present the first comprehensive study of NaCl and KCl gases in Io's atmosphere in order to investigate their characteristics, and to infer properties of Io's volcanoes and subsurface magma ...chambers. In this work, we compile all past spectral line observations of NaCl and KCl in Io's atmosphere from the Atacama Large Millimeter/submillimeter Array (ALMA) and use atmospheric models to constrain the physical properties of the gases on several dates between 2012 and 2018. NaCl and KCl appear to be largely spatially confined and for observations with high spectral resolution, the temperatures are high (~500-1000 K), implying a volcanic origin. The ratio of NaCl:KCl was found to be ~5-6 in June 2015 and ~3.5-10 in June 2016, which is consistent with predictions based on observations of Io's extended atmosphere, and less than half the Na:K ratio in chondrites. Assuming these gases are volcanic in origin, these ratios imply a magma temperature of ~1300 K, such that the magma will preferentially outgas KCl over NaCl.
2013 FY27 is the ninth intrinsically brightest Trans-Neptunian Object (TNO). We observed 2013 FY27 at thermal wavelengths with ALMA and in the optical with Magellan to determine its size and albedo ...for the first time and compare it to other dwarf planets. The geometric albedo of 2013 FY27 was found to be 0.17 -0.030+0.045, giving an effective diameter of D = 765 +80-85 km. 2013 FY27 has a size within the transition region between the largest few TNOs that have higher albedos and higher densities than smaller TNOs. No significant short-term optical light curve was found, with variations less than 0.06 mags over hours and days. The Sloan optical colors of 2013 FY27 are g-r=0.76 +-0.02 and r-i=0.31 +-0.03 mags, which is a moderately red color. This color is different than the neutral or ultra-red colors found for the ten largest TNOs, making 2013 FY27 one of the largest known moderately red TNOs, which only start to be seen, and in abundance, at diameters less than 800 km. This suggests something physically different might be associated with TNOs larger than 800 km. It could be that moderately red surfaces are older or less ice rich and TNOs larger than 800 km have fresher surfaces or are able to hold onto more volatile ices. Its also possible TNOs larger than 800 km are more fully differentiated, giving them different surface compositions. A satellite at 0.17 arcsec away and 3.0 +-0.2 mags fainter than 2013 FY27 was found through Hubble Space Telescope observations. Almost all the largest TNOs have satellites, and the relative small size of 2013 FY27's satellite suggests it was created through a direct collision, similar to satellites known around the largest TNOs. Assuming the satellite has a similar albedo as the primary, it is about 190 km in diameter, making the primary D = 740 +85-90 km.
We present 1-mm observations constructed from ALMA Atacama Large (sub)Millimeter Array data of SO\(_2\), SO and KCl when Io went from sunlight into eclipse (20 March 2018), and vice versa (2 and 11 ...September 2018). There is clear evidence of volcanic plumes on 20 March and 2 September. The plumes distort the line profiles, causing high-velocity (\(\gtrsim\)500 m/s) wings, and red/blue-shifted shoulders in the line profiles. During eclipse ingress, the SO\(_2\) flux density dropped exponentially, and the atmosphere reformed in a linear fashion when re-emerging in sunlight, with a "post-eclipse brightening" after \(\sim\)10 minutes. While both the in-eclipse decrease and in-sunlight increase in SO was more gradual than for SO\(_2\), the fact that SO decreased at all is evidence that self-reactions at the surface are important and fast, and that in-sunlight photolysis of SO\(_2\) is the dominant source of SO. Disk-integrated SO\(_2\) in-sunlight flux densities are \(\sim\)2--3 times higher than in-eclipse, indicative of a roughly 30--50\% contribution from volcanic sources to the atmosphere. Typical column densities and temperatures are \(N \approx (1.5 \pm 0.3) \times 10^{16}\) cm\(^{-2}\) and \(T \approx 220-320\) K both in-sunlight and in-eclipse, while the fractional coverage of the gas is 2--3 times lower in-eclipse than in-sunlight. The low level SO\(_2\) emissions present during eclipse may be sourced by stealth volcanism or be evidence of a layer of non-condensible gases preventing complete collapse of the SO\(_2\) atmosphere. The melt in magma chambers at different volcanoes must differ in composition to explain the absence of SO and SO\(_2\), but simultaneous presence of KCl over Ulgen Patera.
We present thermal observations of Ganymede from the Atacama Large Millimeter Array (ALMA) in 2016-2019 at a spatial resolution of 300-900 km (0.1-0.2'' angular resolution) and frequencies of 97.5, ...233, and 343.5 GHz (wavelengths of 3, 1.3, and 0.87 mm); the observations collectively covered all Ganymede longitudes. We determine the global thermophysical properties using a thermal model that considers subsurface emission and depth- and temperature-dependent thermophysical and dielectric properties, in combination with a retrieval algorithm. The data are sensitive to emission from the upper \(\sim\)0.5 meter of the surface, and we find a millimeter emissivity of 0.75-0.78 and (sub)surface porosities of 10-40%, corresponding to effective thermal inertias of 400-800 J m^{-2} K^{-1} s^{-1/2}. Combined with past infrared results, as well as modeling presented here of a previously-unpublished Galileo PPR nighttime infrared observation, the multi-wavelength constraints are consistent with a compaction profile whereby the porosity drops from ~85% at the surface to 10{+30/-10}% at depth over a compaction length scale of tens of cm. We present maps of temperature residuals from the best-fit global models which indicate localized variations in thermal surface properties at some (but not all) dark terrains and at impact craters, which appear 5-8 K colder than the model. Equatorial regions are warmer than predicted by the model, in particular near the centers of the leading and trailing hemispheres, while the mid-latitudes (~30-60 degrees) are generally colder than predicted; these trends are suggestive of an exogenic origin.
We report observations of the Didymos-Dimorphos binary asteroid system using the Atacama Large Millimeter/Submillimeter Array (ALMA) and the Atacama Compact Array (ACA) in support of the Double ...Asteroid Redirection Test (DART) mission. Our observations on UT 2022 September 15 provided a pre-impact baseline and the first measure of Didymos-Dimorphos' spectral emissivity at \(\lambda=0.87\) mm, which was consistent with the handful of siliceous and carbonaceous asteroids measured at millimeter wavelengths. Our post-impact observations were conducted using four consecutive executions each of ALMA and the ACA spanning from T\(+\)3.52 to T\(+\)8.60 hours post-impact, sampling thermal emission from the asteroids and the impact ejecta. We scaled our pre-impact baseline measurement and subtracted it from the post-impact observations to isolate the flux density of mm-sized grains in the ejecta. Ejecta dust masses were calculated for a range of materials that may be representative of Dimorphos' S-type asteroid material. The average ejecta mass over our observations is consistent with 1.3--6.4\(\times10^7\) kg, with the lower and higher values calculated for amorphous silicates and for crystalline silicates, respectively. Owing to the likely crystalline nature of S-type asteroid material, the higher value is favored. These ejecta masses represent 0.3--1.5\% of Dimorphos' total mass and are in agreement with lower limits on the ejecta mass based on measurements at optical wavelengths. Our results provide the most sensitive measure of mm-sized material in the ejecta and demonstrate the power of ALMA for providing supporting observations to spaceflight missions.
The study of planets and small bodies within our Solar System is fundamental for understanding the formation and evolution the Earth and other planets. Compositional and meteorological studies of the ...giant planets provide a foundation for understanding the nature of the most commonly observed exoplanets, while spectroscopic observations of the atmospheres of terrestrial planets, moons, and comets provide insights into the past and present-day habitability of planetary environments, and the availability of the chemical ingredients for life. While prior and existing (sub)millimeter observations have led to major advances in these areas, progress is hindered by limitations in the dynamic range, spatial and temporal coverage, as well as sensitivity of existing telescopes and interferometers. Here, we summarize some of the key planetary science use cases that factor into the design of the Atacama Large Aperture Submillimeter Telescope (AtLAST), a proposed 50-m class single dish facility: (1) to more fully characterize planetary wind fields and atmospheric thermal structures, (2) to measure the compositions of icy moon atmospheres and plumes, (3) to obtain detections of new, astrobiologically relevant gases and perform isotopic surveys of comets, and (4) to perform synergistic, temporally-resolved measurements in support of dedicated interplanetary space missions. The improved spatial coverage (several arcminutes), resolution (\(\sim1.2''-12''\)), bandwidth (several tens of GHz), dynamic range (\(\sim10^5\)) and sensitivity (\(\sim1\) mK km s\(^{-1}\)) required by these science cases would enable new insights into the chemistry and physics of planetary environments, the origins of prebiotic molecules and the habitability of planetary systems in general.
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