| 1. |
- Meech, K. J., et al.
(författare)
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EPOXI: Comet 103P/Hartley 2 Observations from a Worldwide Campaign
- 2011
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Ingår i: Astrophysical Journal Letters. - London : IOP. - 2041-8213 .- 2041-8205. ; 734:L1, s. 1-9
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Tidskriftsartikel (refereegranskat)abstract
- Earth- and space-based observations provide synergistic information for space mission encounters by providing data over longer timescales, at different wavelengths and using techniques that are impossible with an in situ flyby. We report here such observations in support of the EPOXI spacecraft flyby of comet 103P/Hartley 2. The nucleus is small and dark, and exhibited a very rapidly changing rotation period. Prior to the onset of activity, the period was ~16.4?hr. Starting in 2010 August the period changed from 16.6?hr to near 19?hr in December. With respect to dust composition, most volatiles and carbon and nitrogen isotope ratios, the comet is similar to other Jupiter-family comets. What is unusual is the dominance of CO 2 -driven activity near perihelion, which likely persists out to aphelion. Near perihelion the comet nucleus was surrounded by a large halo of water-ice grains that contributed significantly to the total water production.
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| 2. |
- Davidsson, Björn J. R., et al.
(författare)
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Thermal Inertia and Surface Roughness of Comet 9P/Tempel 1 Derived from Recalibrated Deep Impact NIR Spectroscopy
- 2011
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Ingår i: EPSC-DPS Joint Meeting 2011. ; , s. 221-
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Konferensbidrag (refereegranskat)abstract
- On July 4, 2005, the HRI-IR instrument onboard the Deep Impact spacecraft (NASA/Univ. of Maryland) acquired the first ever near-infrared spectra of a fully resolved comet nucleus, 9P/Tempel 1. Early attempts to estimate the thermal inertia of the surface material were inconclusive, due to negligence of small-scale surface roughness in the thermophysical models used to analyze the spectra. Following a substantial recalibration of the original dataset, we now reconsider the 9P/Tempel 1 spectra, using more realistic thermophysical models. In addition to largescale nucleus irregularity, these models now explicitly consider small-scale roughness and related phenomena such as shadowing and IR self heating. Furthermore, 3D heat conduction can be utilized when topographic features are similar in size to the thermal skin depth, or smaller. Estimates of the thermal inertia, degree of small-scale roughness and their levels of variation across the nucleus are presented.
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| 3. |
- Sierks, H., et al.
(författare)
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Images of Asteroid 21 Lutetia : A Remnant Planetesimal from the Early Solar System
- 2011
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Ingår i: Science. - : American Association for the Advancement of Science (AAAS). - 0036-8075 .- 1095-9203. ; 334:6055, s. 487-490
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Tidskriftsartikel (refereegranskat)abstract
- Images obtained by the Optical, Spectroscopic, and Infrared Remote Imaging System (OSIRIS) cameras onboard the Rosetta spacecraft reveal that asteroid 21 Lutetia has a complex geology and one of the highest asteroid densities measured so far, 3.4 +/- 0.3 grams per cubic centimeter. The north pole region is covered by a thick layer of regolith, which is seen to flow in major landslides associated with albedo variation. Its geologically complex surface, ancient surface age, and high density suggest that Lutetia is most likely a primordial planetesimal. This contrasts with smaller asteroids visited by previous spacecraft, which are probably shattered bodies, fragments of larger parents, or reaccumulated rubble piles.
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