1,038 research outputs found
Vapor pressure isotope fractionation effects in planetary atmospheres: application to deuterium
The impact of the vapor pressure difference between deuterated and
nondeuterated condensing molecules in planetary atmospheres is quantitatively
assessed. This difference results in a loss of deuterium in the vapor phase
above the condensation level. In Titan, Uranus and Neptune, the effect on CH3D
is too subtle to alter current D/H ratio determinations. In Mars, the effect
can induce a large depletion of HDO, starting about one scale height above the
condensation level. Although the current infrared measurements of the D/H ratio
appear to be almost unaffected, the intensity of disk-averaged millimetric HDO
lines can be modified by about 10%. The effect is much stronger in limb
sounding, and can be easily detected from orbiter observations.Comment: 24 pages, 1 table, 6 figures. Paper accepted for publication in
ICARU
Search for signatures of dust in the Pluto-Charon system using Herschel/PACS observations
In this letter we explore the environment of Pluto and Charon in the far
infrared with the main aim to identify the signs of any possible dust ring,
should it exist in the system. Our study is based on observations performed at
70 um with the PACS instrument onboard the Herschel Space Observatory at 9
epochs between March 14 and 19, 2012. The far-infrared images of the
Pluto-Charon system are compared to those of the point spread function (PSF)
reference quasar 3C454.3. The deviation between the observed Pluto-Charon and
reference PSFs are less then 1 sigma indicating that clear evidence for an
extended dust ring around the system was not found. Our method is capable of
detecting a hypothetical ring with a total flux of ~3.3 mJy at a distance of
~153 000 km (~8.2 Pluto-Charon distances) from the system barycentre. We place
upper limits on the total disk mass and on the column density in a reasonable
disk configuration and analyse the hazard during the flyby of NASAs New
Horizons in July 2015. This realistic model configuration predicts a column
density of 8.7x10^(-10) gcm^(-2) along the path of the probe and an impactor
mass of 8.7x10^(-5) g.Comment: 10 pages, 4 figures, 2 table
Pathways to Sustainable Planetary Science : Planetary Science and Astrobiology Decadal Survey 2023-2032 White Paper
Whitepaper #419 submitted to the Planetary Science and Astrobiology Decadal Survey 2023-2032. Topics: state of the professionThis White Paper focuses on how modifying our activities, particularly associated with academic travel, can affect the carbon footprint of the planetary science community, and it makes recommendations on how the community and the funding agencies could best participate in the cultural change required to mitigate the damage that AGW will cause
The albedo-color diversity of transneptunian objects
We analyze albedo data obtained using the Herschel Space Observatory that
reveal the existence of two distinct types of surface among midsized
transneptunian objects. A color-albedo diagram shows two large clusters of
objects, one redder and higher albedo and another darker and more neutrally
colored. Crucially, all objects in our sample located in dynamically stable
orbits within the classical Kuiper belt region and beyond are confined to the
bright-red group, implying a compositional link. Those objects are believed to
have formed further from the Sun than the dark-neutral bodies. This
color-albedo separation is evidence for a compositional discontinuity in the
young solar system.Comment: 16 pages, 4 figures, 1 table, published in ApJL (12 August 2014), The
Astrophysical Journal (2014), vol. 793, L
Physical studies of Centaurs and Trans-Neptunian Objects with the Atacama Large Millimeter Array
Once completed, the Atacama Large Millimeter Array (ALMA) will be the most
powerful (sub)millimeter interferometer in terms of sensitivity, spatial
resolution and imaging. This paper presents the capabilities of ALMA applied to
the observation of Centaurs and Trans-Neptunian Objects, and their possible
output in terms of physical properties. Realistic simulations were performed to
explore the performances of the different frequency bands and array
configurations, and several projects are detailed along with their feasibility,
their limitations and their possible targets. Determination of diameters and
albedos via the radiometric method appears to be possible on ~500 objects,
while sampling of the thermal lightcurve to derive the bodies' ellipticity
could be performed at least 30 bodies that display a significant optical
lightcurve. On a limited number of objects, the spatial resolution allows for
direct measurement of the size or even surface mapping with a resolution down
to 13 milliarcseconds. Finally, ALMA could separate members of multiple systems
with a separation power comparable to that of the HST. The overall performance
of ALMA will make it an invaluable instrument to explore the outer solar
system, complementary to space-based telescopes and spacecrafts.Comment: Accepted for publication in Icarus (23 pages, 7 figures
New laboratory measurements of CH4 in Titan's conditions and a reanalysis of the DISR near-surface spectra at the Huygens landing site
International audienceLaboratory spectra of methane-nitrogen mixtures have been recorded in the near-infrared range (1.0 - 1.65 µm) in conditions similar to Titan's near surface, to facilitate the interpretation of the DISR/DLIS spectra taken during the last phase of the descent of the Huygens Probe, when the surface was illuminated by a surface science lamp. We used a 0.03 cm-1 spectral resolution, adequate to resolve the lines at high pressure (pN2 ~ 1.5 bar). By comparing the laboratory spectra with synthetic calculations in the well-studied ν2 + 2ν3 band (7515-7620 cm-1), we determine a methane absorption column density of 178±20 cm-am and a temperature of 118±10 K in our experiment. From this, we derive the methane absorption coefficients over 1.0-1.65 µm with a 0.03 cm-1 sampling, allowing for the extrapolation of the results to any other methane column density under the relevant pressure and temperature conditions. We then revisit the calibration and analysis of the Titan "lamp-on" DLIS spectra. We infer a 5.1±0.8 % methane mixing ratio in the first 25 m of Titan's atmosphere. The CH4 mixing ratio measured 90 sec after landing from a distance of 45 cm is found to be 0.92±0.25 times this value, thus showing no post-landing outgassing of methane in excess of ̴ 20 %. Finally, we determine the surface reflectivity as seen from 25 m and 45 cm and find that the 1500 nm absorption band is deeper in the post-landing spectrum as compared to pre-landing
Titan Science with the James Webb Space Telescope (JWST)
The James Webb Space Telescope (JWST), scheduled for launch in 2018, is the
successor to the Hubble Space Telescope (HST) but with a significantly larger
aperture (6.5 m) and advanced instrumentation focusing on infrared science
(0.6-28.0 m ). In this paper we examine the potential for scientific
investigation of Titan using JWST, primarily with three of the four
instruments: NIRSpec, NIRCam and MIRI, noting that science with NIRISS will be
complementary. Five core scientific themes are identified: (i) surface (ii)
tropospheric clouds (iii) tropospheric gases (iv) stratospheric composition and
(v) stratospheric hazes. We discuss each theme in depth, including the
scientific purpose, capabilities and limitations of the instrument suite, and
suggested observing schemes. We pay particular attention to saturation, which
is a problem for all three instruments, but may be alleviated for NIRCam
through use of selecting small sub-arrays of the detectors - sufficient to
encompass Titan, but with significantly faster read-out times. We find that
JWST has very significant potential for advancing Titan science, with a
spectral resolution exceeding the Cassini instrument suite at near-infrared
wavelengths, and a spatial resolution exceeding HST at the same wavelengths. In
particular, JWST will be valuable for time-domain monitoring of Titan, given a
five to ten year expected lifetime for the observatory, for example monitoring
the seasonal appearance of clouds. JWST observations in the post-Cassini period
will complement those of other large facilities such as HST, ALMA, SOFIA and
next-generation ground-based telescopes (TMT, GMT, EELT).Comment: 50 pages, including 22 figures and 2 table
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