Detection of Abundant Ethane and Methane, Along with Carbon Monoxide and Water, in Comet C/1996 B2 Hyakutake: Evidence for Interstellar Origin

Mumma, M. J.; DiSanti, M. A.; Russo, N. Dello; Fomenkova, M. N.; Magee-Sauer, K.; Kaminski, C.; Xie, D. X.

doi:10.1126/science.272.5266.1310

Cited by 308 publications

(194 citation statements)

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“…Our calculations assume that the Einstein A values for the lines in this band are identical to the Einstein A values for the lines in the ν 2 + ν 3 band, an assumption that was used previously by Mumma et al (1996) in their analysis of the H 2 O lines they observed in Comet Hyakutake (1996 B2) and which gave production rates that were comparable to those derived using other techniques (e.g., observations of OH). A recent ab initio calculation of the intensities of H 2 O lines (Partridge and Schwenke 1997) also gives excellent agreement (within 2%) with our estimate for the strength of the 2 02 − 3 03 line.…”

Section: H 2 Omentioning

confidence: 57%

“…For T rot = 100 K, the abundance ratio limit is ∼4-6%. Our limit on CO production in GZ is similar to the estimated abundance of CO in the nucleus of Comets 1P/Halley (3.5%, Eberhardt 1998), Bradfield (C/1979 Y1) (3.5%, Feldman et al 1997), and Levy (C/1990 K1) (4.1-8.4%, Feldman et al 1997), and is significantly lower than the estimated CO abundances in comets Hyakutake (C/1996 B2) (∼14%, McPhate et al 1996; ∼20%, Biver et al 1999b;Mumma et al 1996 derived a preliminary value of 7%) and Hale-Bopp (∼10% at r ∼ 1 AU, according to Weaver et al 1999 andDiSanti et al 1999; ∼23% at r ∼ 1 AU, according to Biver et al 1999a). The CO abundance limit for GZ is somewhat larger than the abundance ratio observed in Comet Austin (C/1989 X1) (1.7%, Feldman et al 1997) and the upper limits derived for 103P/Hartley 2 (≤1.2%, Weaver et al 1994) and Shoemaker-Levy (C/1991 T2) (≤1.8%, Feldman et al 1997).…”

Section: Comentioning

confidence: 83%

“…Similarly, the CSHELL point near 4.67 µm was multiplied by 1.6 to convert from a 1 × 4 aperture to a 2 × 4 aperture. abundant C 2 H 6 (Mumma et al 1996). The Q subbranches of this molecule are very strong and many fall at wavelengths where there is good transmittance through the terrestrial atmosphere, so sensitive searches for C 2 H 6 are possible.…”

Section: Hmentioning

confidence: 99%

“…(1995), except for GZ (this work). e Q C 2 H 6 : assumes residual emission at 3.35 µm is due to the C 2 H 6 ν 7 band; for Comets Hyakutake and Hale-Bopp, C 2 H 6 production rates are based on clear identifications of several subbranches in the C 2 H 6 ν 7 band (Mumma et al 1996, Weaver et al 1999, Kim et al 2000 but the values are preliminary.…”

Section: Hmentioning

confidence: 99%

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An Infrared Investigation of Volatiles in Comet 21P/Giacobini–Zinner

Weaver¹,

Chin

Bockelée‐Morvan

et al. 1999

Icarus

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We obtained high resolution (λ/δλ ∼ 10,000-20,000) infrared (IR) spectra of Comet 21P/Giacobini-Zinner (GZ) at five different wavelengths between 1.9 and 5.0 µm during 25-29 October 1998 using CSHELL at the NASA Infrared Telescope Facility (IRTF) on Mauna Kea. We also obtained a moderate resolution (λ/δλ ∼ 680) spectrum covering the wavelength range from 3.082 to 3.720 µm on 29 October 1998 using CGS4 at the United Kingdom Infrared Telescope (UKIRT) on Mauna Kea. Five rovibrational lines in three different vibrational bands of H 2 O were detected in the CSHELL spectra. Assuming that the rotational temperature was ∼50 K, we derive a H 2 O production rate of ∼2-3 × 10 28 molecules s −1 , which is ∼2 times smaller than the value derived from nearly simultaneous radio observations of OH. After continuum subtraction, the CGS4 spectrum displays significant excess flux that we attribute mainly to CH 3 OH fluorescence, and we derive that the CH 3 OH production rate was ∼2.7 × 10 26 molecules s −1 . The corresponding CH 3 OH/H 2 O relative abundance is ∼0.9-1.4%, which falls within the range of values observed in other comets, albeit at the low end. The CGS4 spectrum also has significant excess flux near 3.43 µm that is not explained by our CH 3 OH fluorescence model; a similar feature has been observed in several other comets, but its origin remains a mystery. We did not detect any excess emission near 3.28 µm, where some comets show a feature that may be associated with polycyclic aromatic hydrocarbons. We also searched for emissions from C 2 H 6 , CO, HCN, C 2 H 2 , and H 2 CO but did not detect any of these molecules. The 3σ upper limits for the abundances relative to H 2 O are 0.05-0.08% for C 2 H 6 , 2-3% for CO, 0.2-0.3% for HCN, 0.3-0.4% for C 2 H 2 , and 0.5-0.8% for H 2 CO, assuming that all species are parent molecules and that their rotational temperature in the coma is 50 K. C 2 H 6 is depleted by a factor of ∼15 or more compared to its relative abundance in Comets Hale-Bopp VOLATILES IN COMET 21P/GZ 483 (C/1995 O1) and Hyakutake (C/1996 B2); this depletion is similar to that observed for C 2 and C 3 from optical observations of GZ (A'Hearn et al. 1995) and suggests that the formation of volatile carbon-chain molecules was inhibited in GZ. We are unable to find any clear correlation between the C 2 H 6 and the C 2 and C 3 abundances in a sample of nine other comets, assuming that the residual emission near 3.35 µm in moderate resolution spectra of seven of the comets provides an accurate indicator of the C 2 H 6 abundance. However, this latter assumption is questionable and highlights the need to obtain high spectral resolution data in order to make accurate abundance measurements of C 2 H 6 .

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Section: H 2 Omentioning

confidence: 57%

Section: Comentioning

confidence: 83%

Section: Hmentioning

confidence: 99%

Section: Hmentioning

confidence: 99%

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An Infrared Investigation of Volatiles in Comet 21P/Giacobini–Zinner

Weaver¹,

Chin

Bockelée‐Morvan

et al. 1999

Icarus

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“…If it occurred it would lead by hydrogenation to the presence of significant amounts of * C 2 H 6 , not currently detected. C 2 H 6 is seen in the cometry coma of comets Hyakutake and Hale-Bopp (Mumma et al 1996) and it is not known if this formed on the surface or in the gas phase. The bulk of surface reactions comprise routes to the complex molecules * CH 3 OH, * C 2 H 5 OH and * CH 3 OCH 3 .…”

Section: Reaction Setmentioning

confidence: 99%

Complex molecule formation in grain mantles

Hall

Millar

2010

A&A

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Context. Complex molecules such as ethanol and dimethyl ether have been observed in a number of hot molecular cores and hot corinos. Attempts to model the molecular formation process using gas phase only models have so far been unsuccessful. Aims. To demonstrate that grain surface processing is a viable mechanism for complex molecule formation in these environments. Methods. A variable environment parameter computer model has been constructed which includes both gas and surface chemistry. This is used to investigate a variety of cloud collapse scenarios.Results. Comparison between model results and observation shows that by combining grain surface processing with gas phase chemistry complex molecules can be produced in observed abundances in a number of core and corino scenarios. Differences in abundances are due to the initial atomic and molecular composition of the core/corino and varying collapse timescales. Conclusions. Grain surface processing, combined with variation of physical conditions, can be regarded as a viable method for the formation of complex molecules in the environment found in the vicinity of a hot core/corino and produce abundances comparable to those observed.

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Apollo 17 and the Moon

Schmitt

2003

Encyclopedia of Space Science and Technology

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Apollo 17 was not the last flight of humans to the Moon. More lunar exploration and even lunar settlement will occur, baring the future stagnation or disappearance of our civilization. Exploration and scientific investigations in the earth sciences are rarely complete, particularly for studies related to a specific field site. A long hiatus between field investigations may occur, but other forms of investigation, directly or indirectly related, continue. Apollo 17's field study of the Valley of Taurus‐Littrow on the Moon in 1972 and subsequent examination of its significance to our understanding of the origin and evolution of that small planet and of our own constitute a good example of these facts of scientific life. As the third of the specifically “science” missions to the Moon in the twentieth century, Apollo 17 actually became the last lunar landing of the Apollo Program in September 1970 rather than on 11 December 1972 when the mission reached Taurus‐Littrow. The National Aeronautics and Space Administration (NASA) and the Administration of President Richard M. Nixon, with the acquiescence of the Congress, had concluded that no further planned amortization of the American taxpayer's investment in deep space exploration would be undertaken. The scientists became increasingly interested in an unnamed, 2300‐m deep, 50‐km long valley, radial to the 740‐km diameter circular basin, Serenitatis, that cut through the Taurus Mountain ring near the crater Littrow. This Valley of “Taurus‐Littrow,” however, was not a favorite of the operational mission planners. In spite of the pinpoint landing accuracy they had demonstrated on all previous missions since Apollo 11, the narrow valley, the mountainous approach, and the high valley walls gave the planners pause. Their legitimate concerns were compounded by the relatively short time, only 14 minutes, for navigational updates after acquisition of communications from the lunar module, Challenger, as its last orbit before landing carried it around the Moon from the farside. Initially, trajectory calculations indicated that three‐sigma errors, the normal extremely conservative planning limit, might result in hitting the side of the northern mountain wall. Gradually, however, refinements in navigational techniques for the mission and the inevitable synergistic give and take that so characterized Apollo interactions narrowed the three‐sigma errors to about 1 km, the limit where all agreed that Taurus‐Littrow could be the selected site. Thus, in late February 1972, only 9 months from launch, Taurus‐Littrow was approved as the exploration site for Apollo 17. The Valley of Taurus‐Littrow offered four major benefits as the last Apollo landing site, taken in the context of a final test of then current hypotheses related to the origin and evolution of the Moon. First, photogeologic analysis indicated that Taurus‐Littrow provided access to a three‐dimensional window into a mountain ring created by the Serenitatis large basin‐forming event, by now well established as the result of a giant impact of an asteroid or comet. Second, major units of mare basalt and older nonmare rocks would be within easy reach of roving vehicle traverses. Third, a mantle of dark, possibly young volcanic debris partially covered the region as well as portions of the valley, and craters of a range of depths penetrated this debris and the underlying basalt. And, fourth, the valley lies about 600 km north and 200 km east of the Apollo 11 and Apollo 15 sample areas, respectively, adding significantly to our exploration coverage of the Moon's nearside. Due to the foreknowledge that Apollo 17 would be the last of the Apollo series, selection of its landing site became a contentious issue among lunar scientists and between lunar scientists and operational planners. Impact cratering, origin and evolution of the Moon were subjects of Apollo 17's scientific informers and enquiries and are discussed.

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Detection of Abundant Ethane and Methane, Along with Carbon Monoxide and Water, in Comet C/1996 B2 Hyakutake: Evidence for Interstellar Origin

Cited by 308 publications

References 33 publications

An Infrared Investigation of Volatiles in Comet 21P/Giacobini–Zinner

An Infrared Investigation of Volatiles in Comet 21P/Giacobini–Zinner

Complex molecule formation in grain mantles

Apollo 17 and the Moon

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