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Comet 81P/Wild is at Opposition (3.480 AU) on the 24th October 2014 

Ephemeris

Date    TT    R. A. (2000) Decl.     Delta      r    Elong.  Phase   Mag
2014 10 23    02 00 38.8 +08 01 03   3.4830  4.4759   175.7     1.0  19.5  23.1
2014 10 24    01 59 56.8 +07 57 05   3.4798  4.4727   176.0     0.9  19.5  23.1
2014 10 25    01 59 14.8 +07 53 08   3.4769  4.4695   175.9     0.9  19.5  23.1
2014 10 26    01 58 32.6 +07 49 11   3.4744  4.4663   175.5     1.0  19.5  23.1
2014 10 27    01 57 50.4 +07 45 14   3.4721  4.4631   174.9     1.1  19.4  23.1
2014 10 28    01 57 08.3 +07 41 19   3.4702  4.4598   174.1     1.3  19.4  23.1
2014 10 29    01 56 26.1 +07 37 25   3.4686  4.4566   173.2     1.5  19.4  23.1
2014 10 30    01 55 44.0 +07 33 32   3.4673  4.4534   172.2     1.7  19.4  23.2
2014 10 31    01 55 02.1 +07 29 41   3.4664  4.4501   171.1     2.0  19.4  23.2


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Comet 81P/Wild is at Opposition (4.244 AU) on the 29th September 2013



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Title: The origin of the 3.4 micron feature in Wild 2 cometary particles and in ultracarbonaceous interplanetary dust particles
Authors: Graciela Matrajt, George Flynn, Don Brownlee, Dave Joswiak, Sasa Bajt

We analysed 2 ultra-carbonaceous interplanetary dust particles and 2 cometary Wild 2 particles with infrared spectroscopy. We characterised the carrier of the 3.4 micron band in these samples and compared its profile and the CH2/CH3 ratios to the 3.4 micron band in the diffuse interstellar medium (DISM), in the insoluble organic matter (IOM) from 3 primitive meteorites, in asteroid 24 Themis and in the coma of comet 103P/Hartley 2. We found that the 3.4 micron band in both Wild 2 and IDPs is similar, but different from all the other astrophysical environments that we compared to. The 3.4 micron band in IDPs and Wild 2 particles is dominated by CH2 groups, the peaks are narrower and stronger than in the meteorites, asteroid Themis, and the DISM. Also, the presence of the carbonyl group C=O at 1700 cm-1 (5.8 micron) in most of the spectra of our samples, indicates that these aliphatic chains have O bonded to them, which is quite different from astronomical spectra of the DISM. Based on all these observations we conclude that the origin of the carrier of the 3.4 micron band in IDPs and Wild 2 samples is not interstellar, instead, we suggest that the origin lies in the outermost parts of the solar nebula.

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Comet Wild2: First Evidence of Space Weathering

The traditional picture of comets as cold, icy, unchanging bodies throughout their history is being reappraised in the light of analyses of dust grains from Comet Wild2. A team led by the University of Leicester has detected the presence of iron in a dust grain, evidence of space weathering that could explain the rusty reddish colour of Wild2's outer surface. The results will be presented by Dr John Bridges at the National Astronomy Meeting in Manchester on Tuesday 27th March.
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UH scientists analyse comet grain to estimate age of Jupiter

Jupiter ploughs through the solar system like a giant vacuum cleaner, sucking up rocks and dust with its massive gravity.
That's been going on for about 4.565 billion years, University of Hawaii scientists reckon by studying a grain of comet dust.
Particles from Comet Wild 2 were brought back to Earth by NASA's Stardust spacecraft in 2006. One was a fragment formed by high-temperature processes in the cloud that surrounded the sun in its infancy.

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Title: Incorporation of a Late-forming Chondrule into Comet Wild 2
Authors: R. C. Ogliore, G. R. Huss, K. Nagashima, A. L. Butterworth, Z. Gainsforth, J. Stodolna, A. J. Westphal, D. Joswiak, T. Tyliszczak

We report the petrology, O isotopic composition, and Al-Mg isotope systematics of a chondrule fragment from the Jupiter-family comet Wild 2, returned to Earth by NASA's Stardust mission. This object shows characteristics of a type II chondrule that formed from an evolved oxygen isotopic reservoir. No evidence for extinct 26Al was found, with (26Al/ 27Al)0 < 3.0 x 10^-6. Assuming homogenous distribution of 26Al in the solar nebula, this particle crystallised at least 3 Myr after the earliest solar system objects-relatively late compared to most chondrules in meteorites. We interpret the presence of this object in a Kuiper Belt body as evidence of late, large-scale transport of small objects between the inner and outer solar nebula. Our observations constrain the formation of Jupiter (a barrier to outward transport if it formed further from the Sun than this cometary chondrule) to be more than 3 Myr after CAIs.

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Shooting Iron Sulphides into Aluminium Foil to Better Understand Comet Wild 2

When NASA's Stardust mission returned samples from comet 81P/Wild 2 to Earth in 2006, researchers found particles in the aerogel collector-cells as well as in the aluminium (Al) foil, which wrapped the cells and facilitated the safe removal of the aerogel from the collector frame. These Al-foil pull tabs, though not the primary collecting material, captured a bonus assortment of cometary grains. But did the impacts into the Al foil change the Wild 2 grains? Teams of scientists have been hard at work in the laboratory to answer that question by simulating impacts into Stardust Al foil using a light gas gun to shoot powders of the major minerals found in cometary dust.
They are studying the impact craters on the Al foils and what's left of the impacting particles, the residues, that coat the crater surfaces. Whether or not the original chemical composition of the impacting particle is preserved in the residue is a key question to examine in the laboratory, as the answer bears on how accurately the researchers can determine the original chemistry of the cometary grains from Wild 2.

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Frozen Comet Had a Watery Past, UA Scientists Find

The discovery of minerals requiring liquid water for their formation challenges the paradigm of comets as "dirty snowballs" frozen in time.
For the first time, scientists have found convincing evidence for the presence of liquid water in a comet, shattering the current paradigm that comets never get warm enough to melt the ice that makes up the bulk of their material.

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The magnitude 13.9 comet 81P/Wild 2 will pass 0.32° from the magnitude 11.5 galaxy NGC 5878, in the constellation Libra, at 23:00 UT, 7th August, 2010.

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Title: Water production in comet 81P/Wild 2 as determined by Herschel/HIFI
Authors: M. de Val-Borro, P. Hartogh, J. Crovisier, D. Bockelée-Morvan, N. Biver, D. C. Lis, R. Moreno, C. Jarchow, M. Rengel, S. Szutowicz, M. Banaszkiewicz, F. Bensch, M. I. Blecka, M. Emprechtinger, T. Encrenaz, E. Jehin, M. Küppers, L.-M. Lara, E. Lellouch, B. M. Swinyard, B. Vandenbussche, E. A. Bergin, G. A. Blake, J. A. D. L. Blommaert, J. Cernicharo, L. Decin, P. Encrenaz, T. de Graauw, D. Hutsemékers, M. Kidger, J. Manfroid, A. S. Medvedev, D. A. Naylor, R. Schieder, D. Stam, N. Thomas, C. Waelkens, R. Szczerba, P. Saraceno, A. M. Di Giorgio, S. Philipp, T. Klein, V. Ossenkopf, P. Zaal, R. Shipman

The high spectral resolution and sensitivity of Herschel/HIFI allows for the detection of multiple rotational water lines and accurate determinations of water production rates in comets. In this letter we present HIFI observations of the fundamental 110-101 (557 GHz) ortho and 111-000 (1113 GHz) para rotational transitions of water in comet 81P/Wild 2 acquired in February 2010. We mapped the extent of the water line emission with five point scans. Line profiles are computed using excitation models which include excitation by collisions with electrons and neutrals and solar infrared radiation. We derive a mean water production rate of 1.0 x 10^{28} molecules s^{-1} at a heliocentric distance of 1.61 AU about 20 days before perihelion, in agreement with production rates measured from the ground using observations of the 18-cm OH lines. Furthermore, we constrain the electron density profile and gas kinetic temperature, and estimate the coma expansion velocity by fitting the water line shapes.

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