Surface of Young Jupiter Family Comet 81P/Wild 2: View from the Stardust Spacecraft

Brownlee, D. E.; Hörz, Friedrich; Newburn, R. L.; Zolensky, M. E.; Duxbury, T.; Sandford, Scott A.; Sekanina, Z.; Tsou, P.; Hanner, M. S.; Clark, B. C.; Green, Simon; Kissel, J.

doi:10.1126/science.1097899

Cited by 311 publications

(255 citation statements)

References 15 publications

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“…The spacecraft flew within 236 km of the comet's 4.5 km diameter nucleus. Cometary grains were collected during a flyby encounter by passive implantation into aerogel, a low-density silica foam, and by impacting onto the aluminum frame (Brownlee et al 2003(Brownlee et al , 2004. On January 15th, 2006, the Stardust sample container returned safely to Earth, delivering the first cometary samples for laboratory analysis (Brownlee et al 2006;Brownlee 2014).…”

Section: Stardustmentioning

confidence: 99%

Cometary Isotopic Measurements

et al. 2015

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Section: Stardustmentioning

confidence: 99%

Cometary Isotopic Measurements

et al. 2015

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“…Each of the independent variables (color temperature, area, and duration) can be directly related in laboratory impact experiments in order to test the assumption that η is approximately constant for a given target. Such measurements are part of an ongoing experimental study for the radiation from the thermal (Ernst and Schultz, 2002, 2004 and atomic/molecular emission lines (Sugita and Schultz, 1999;Sugita et al, 1998;Sugita and Schultz, 2003a, b;Schultz, 2003, 2004).…”

Section: Integrated Luminous Intensitymentioning

confidence: 99%

“…Recent results from encounters with Comets Borelly (Soderblom et al, 2002) and Wild 2 (Brownlee et al, 2004) have provided unprecedented views of cometary surfaces at scales of 100 m's. It is the response of the surface and substrate at meter scales to the Deep Impact collision, however, that will affect what is observed.…”

Section: Introductionmentioning

confidence: 99%

Expectations for Crater Size and Photometric Evolution from the Deep Impact Collision

Schultz

Ernst

Anderson

Deep Impact Mission: Looking Beneath the Surface of a Cometary Nucleus

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Abstract. The NASA Discovery Deep Impact mission involves a unique experiment designed to excavate pristine materials from below the surface of comet. In July 2005, the Deep Impact (DI) spacecraft, will release a 360 kg probe that will collide with comet 9P/Tempel 1. This collision will excavate pristine materials from depth and produce a crater whose size and appearance will provide fundamental insights into the nature and physical properties of the upper 20 to 40 m. Laboratory impact experiments performed at the NASA Ames Vertical Gun Range at NASA Ames Research Center were designed to assess the range of possible outcomes for a wide range of target types and impact angles. Although all experiments were performed under terrestrial gravity, key scaling relations and processes allow first-order extrapolations to Tempel 1. If gravity-scaling relations apply (weakly bonded particulate near-surface), the DI impact could create a crater 70 m to 140 m in diameter, depending on the scaling relation applied. Smaller than expected craters can be attributed either to the effect of strength limiting crater growth or to collapse of an unstable (deep) transient crater as a result of very high porosity and compressibility. Larger then expected craters could indicate unusually low density (<0.3 g cm −3 ) or backpressures from expanding vapor. Consequently, final crater size or depth may not uniquely establish the physical nature of the upper 20 m of the comet. But the observed ejecta curtain angles and crater morphology will help resolve this ambiguity. Moreover, the intensity and decay of the impact "flash" as observed from Earth, space probes, or the accompanying DI flyby instruments should provide critical data that will further resolve ambiguities.

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“…Such materials were found to have D/H ratios higher than the SMOW, ranging from moderate excess (1-3× in Stardust samples) to extreme D enrichments (10-30× in UCAMMs, even up to 50× in CPIDPs) (Messenger 2000; Brownlee et al 2004;McKeegan et al 2006;Duprat et al 2010). Given other surface enrichment mechanisms for Solar objects, e.g., spallation reactions (Stephant & Robert 2014), it appears plausible that the 67P crust and dust surfaces contain excess D, bonded directly to primitive organics (Remusat et al 2006) or in hydroxyl groups in silicates (Mahaffy et al 2015).…”

Section: Energetic Water Ions and Deuterium-enriched Cometary Mattermentioning

confidence: 99%

“…Dust particles of cometary origin have also been sampled from comet 81P/Wild_2 (Stardust mission; Brownlee et al 2004;McKeegan et al 2006), collected in Earth's stratosphere (chondritic porous interplanetary dust particles, CP-IDPs; Messenger 2000), and recovered from Antarctic snow (ultracarbonaceous Antarctic micrometeorites, UCAMMs; Duprat et al 2010). Such materials were found to have D/H ratios higher than the SMOW, ranging from moderate excess (1-3× in Stardust samples) to extreme D enrichments (10-30× in UCAMMs, even up to 50× in CPIDPs) (Messenger 2000; Brownlee et al 2004;McKeegan et al 2006;Duprat et al 2010).…”

Section: Energetic Water Ions and Deuterium-enriched Cometary Mattermentioning

confidence: 99%

Dynamic Deuterium Enrichment in Cometary Water via Eley–rideal Reactions

Yao

Giapis

2017

ApJ

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The deuterium-to-hydrogen ratio (D/H) in water found in the coma of Jupiter family comet (JFC) 67P/ Churyumov-Gerasimenko was reported to be (5.3±0.7)×10 −4 , the highest among comets and three times the value for other JFCs with an ocean-like ratio. This discrepancy suggests the diverse origins of JFCs and clouds the issue of the origin of Earth's oceanic water. Here we demonstrate that Eley-Rideal reactions between accelerated water ions and deuterated cometary surface analogs can lead to instantaneous deuterium enrichment in water scattered from the surface. The reaction proceeds with H 2 O + abstracting adsorbed D atoms, forming an excited H 2 DO * state, which dissociates subsequently to produce energetic HDO. Hydronium ions are also produced readily by the abstraction of H atoms, consistent with H 3 O + detection and abundance in various comets. Experiments with water isotopologs and kinematic analysis on deuterated platinum surfaces confirmed the dynamic abstraction mechanism. The instantaneous fractionation process is independent of the surface temperature and may operate on the surface of cometary nuclei or dust grains, composed of deuterium-rich silicates and carbonaceous chondrites. The requisite energetic water ions have been detected in the coma of 67P in two populations. This dynamic fractionation process may temporarily increase the water D/H ratio, especially as the comet gets closer to the Sun. The magnitude of the effect depends on the water ion energy-flux and the deuterium content of the exposed cometary surfaces.

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Surface of Young Jupiter Family Comet 81P/Wild 2: View from the Stardust Spacecraft

Cited by 311 publications

References 15 publications

Cometary Isotopic Measurements

Cometary Isotopic Measurements

Expectations for Crater Size and Photometric Evolution from the Deep Impact Collision

Dynamic Deuterium Enrichment in Cometary Water via Eley–rideal Reactions

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