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See detailThe science case for an orbital mission to Uranus: Exploring the origins and evolution of ice giant planets
Arridge, C. S.; Achilleos, N.; Agarwal, J. et al

in Planetary and Space Science (2014), (0), -

Abstract Giant planets helped to shape the conditions we see in the Solar System today and they account for more than 99% of the mass of the Sun's planetary system. They can be subdivided into the Ice ... [more ▼]

Abstract Giant planets helped to shape the conditions we see in the Solar System today and they account for more than 99% of the mass of the Sun's planetary system. They can be subdivided into the Ice Giants (Uranus and Neptune) and the Gas Giants (Jupiter and Saturn), which differ from each other in a number of fundamental ways. Uranus, in particular is the most challenging to our understanding of planetary formation and evolution, with its large obliquity, low self-luminosity, highly asymmetrical internal field, and puzzling internal structure. Uranus also has a rich planetary system consisting of a system of inner natural satellites and complex ring system, five major natural icy satellites, a system of irregular moons with varied dynamical histories, and a highly asymmetrical magnetosphere. Voyager 2 is the only spacecraft to have explored Uranus, with a flyby in 1986, and no mission is currently planned to this enigmatic system. However, a mission to the uranian system would open a new window on the origin and evolution of the Solar System and would provide crucial information on a wide variety of physicochemical processes in our Solar System. These have clear implications for understanding exoplanetary systems. In this paper we describe the science case for an orbital mission to Uranus with an atmospheric entry probe to sample the composition and atmospheric physics in Uranus’ atmosphere. The characteristics of such an orbiter and a strawman scientific payload are described and we discuss the technical challenges for such a mission. This paper is based on a white paper submitted to the European Space Agency's call for science themes for its large-class mission programme in 2013. [less ▲]

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See detailFirst results of Herschel-PACS observations of Neptune
Lellouch, E.; Hartogh, P.; Feuchtgruber, H. et al

in Astronomy and Astrophysics (2010), 518

We report on the initial analysis of a Herschel-PACS full range spectrum of Neptune, covering the 51-220 μm range with a mean resolving power of ~3000, and complemented by a dedicated observation of CH ... [more ▼]

We report on the initial analysis of a Herschel-PACS full range spectrum of Neptune, covering the 51-220 μm range with a mean resolving power of ~3000, and complemented by a dedicated observation of CH[SUB]4[/SUB] at 120 μm. Numerous spectral features due to HD (R(0) and R(1)), H[SUB]2[/SUB]O, CH[SUB]4[/SUB], and CO are present, but so far no new species have been found. Our results indicate that (i) Neptune's mean thermal profile is warmer by ~3 K than inferred from the Voyager radio-occultation; (ii) the D/H mixing ratio is (4.5 ± 1) × 10[SUP]-5[/SUP], confirming the enrichment of Neptune in deuterium over the protosolar value (~2.1 × 10[SUP]-5[/SUP]); (iii) the CH[SUB]4[/SUB] mixing ratio in the mid stratosphere is (1.5 ± 0.2) × 10[SUP]-3[/SUP], and CH[SUB]4[/SUB] appears to decrease in the lower stratosphere at a rate consistent with local saturation, in agreement with the scenario of CH[SUB]4[/SUB] stratospheric injection from Neptune's warm south polar region; (iv) the H[SUB]2[/SUB]O stratospheric column is (2.1 ± 0.5) × 10[SUP]14[/SUP] cm[SUP]-2[/SUP] but its vertical distribution is still to be determined, so the H[SUB]2[/SUB]O external flux remains uncertain by over an order of magnitude; and (v) the CO stratospheric abundance is about twice the tropospheric value, confirming the dual origin of CO suspected from ground-based millimeter/submillimeter observations. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. [less ▲]

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See detailThe Herschel-SPIRE submillimetre spectrum of Mars
Swinyard, B. M.; Hartogh, P.; Sidher, S. et al

in Astronomy and Astrophysics (2010), 518

We have obtained the first continuous disk averaged spectrum of Mars from 450 to 1550 Ghz using the Herschel-SPIRE Fourier-transform spectrometer. The spectrum was obtained at a constant resolution of 1.4 ... [more ▼]

We have obtained the first continuous disk averaged spectrum of Mars from 450 to 1550 Ghz using the Herschel-SPIRE Fourier-transform spectrometer. The spectrum was obtained at a constant resolution of 1.4 GHz across the whole band. The flux from the planet is such that the instrument was operated in “bright source” mode to prevent saturation of the detectors. This was the first successful use of this mode and in this work we describe the method used for observing Mars together with a detailed discussion of the data reduction techniques required to calibrate the spectrum. We discuss the calibration accuracy obtained and describe the first comparison with surface and atmospheric models. In addition to a direct photometric measurement of the planet the spectrum contains the characteristic transitions of [SUP]12[/SUP]CO from J 5-4 to J 13-12 as well as numerous H[SUB]2[/SUB]O transitions. Together these allow the comparison to global atmospheric models allowing the mean mixing ratios of water and [SUP]12[/SUP]CO to be investigated. We find that it is possible to match the observed depth of the absorption features in the spectrum with a fixed water mixing ratio of 1×10[SUP]-4[/SUP] and a [SUP]12[/SUP]CO mixing ratio of 9×10[SUP]-4[/SUP]. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. [less ▲]

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See detailWater and related chemistry in the solar system. A guaranteed time key programme for Herschel
Hartogh, P.; Lellouch, E.; Crovisier, J. et al

in Planetary and Space Science (2009), 57

â Water and related chemistry in the Solar Systemâ is a Herschel Space Observatory Guaranteed-Time Key Programme. This project, approved by the European Space Agency, aims at determining the distribution ... [more ▼]

â Water and related chemistry in the Solar Systemâ is a Herschel Space Observatory Guaranteed-Time Key Programme. This project, approved by the European Space Agency, aims at determining the distribution, the evolution and the origin of water in Mars, the outer planets, Titan, Enceladus and the comets. It addresses the broad topic of water and its isotopologues in planetary and cometary atmospheres. The nature of cometary activity and the thermodynamics of cometary comae will be investigated by studying water excitation in a sample of comets. The D/H ratio, the key parameter for constraining the origin and evolution of Solar System species, will be measured for the first time in a Jupiter-family comet. A comparison with existing and new measurements of D/H in Oort-cloud comets will constrain the composition of pre-solar cometary grains and possibly the dynamics of the protosolar nebula. New measurements of D/H in giant planets, similarly constraining the composition of proto-planetary ices, will be obtained. The D/H and other isotopic ratios, diagnostic of Marsâ atmosphere evolution, will be accurately measured in H[SUB]2[/SUB]O and CO. The role of water vapor in Marsâ atmospheric chemistry will be studied by monitoring vertical profiles of H[SUB]2[/SUB]O and HDO and by searching for several other species (and CO and H[SUB]2[/SUB]O isotopes). A detailed study of the source of water in the upper atmosphere of the Giant Planets and Titan will be performed. By monitoring the water abundance, vertical profile, and input fluxes in the various objects, and when possible with the help of mapping observations, we will discriminate between the possible sources of water in the outer planets (interplanetary dust particles, cometary impacts, and local sources). In addition to these inter-connected objectives, serendipitous searches will enhance our knowledge of the composition of planetary and cometary atmospheres. [less ▲]

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See detailWater and related chemistry in the Solar System. A Guaranteed Time Key Programme for Herschel
Hartogh, P.; Crovisier, J.; Lellouch, E. et al

in EPSC Abstracts 2009 (2009)

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