Liquid water and organics in Comets: implications for exobiology

Wickramasinghe, J. T.; Wickramasinghe, N. C.; Wallis, M. K.

doi:10.1017/s1473550409990127

Cited by 25 publications

(18 citation statements)

References 19 publications

(32 reference statements)

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“…Could liquid water have existed inside comets as small as Wild 2? Wickramasinghe et al. (2009) described a scenario where a strong cometary crust could conceivably contain steady‐state pressure above the water triple point and retain liquid water in small comets, but this model seems contrived.…”

Section: Aqueous Alteration In Comets?mentioning

confidence: 99%

Overview of the rocky component of Wild 2 comet samples: Insight into the early solar system, relationship with meteoritic materials and the differences between comets and asteroids

Brownlee¹,

Joswiak

Matrajt

2012

Meteorit & Planetary Scien

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Abstract-The solid 2-10 lm samples of comet Wild 2 provide a limited but direct view of the solar nebula solids that accreted to form Jupiter family comets. The samples collected by the Stardust mission are dominated by high-temperature materials that are closely analogous to meteoritic components. These materials include chondrule and CAI-like fragments. Five presolar grains have been discovered, but it is clear that isotopically anomalous presolar grains are only a minor fraction of the comet. Although uncertain, the presolar grain content is perhaps higher than found in chondrites and most interplanetary dust particles. It appears that the majority of the analyzed Wild 2 solids were produced in high-temperature ''rock forming'' environments, and they were then transported past the orbit of Neptune, where they accreted along with ice and organic components to form comet Wild 2. We hypothesize that Wild 2 rocky components are a sample of a ubiquitously distributed flow of nebular solids that was accreted by all bodies including planets and meteorite parent bodies. A primary difference between asteroids and the rocky content of comets is that comets are dominated by this widely distributed component. Asteroids contain this component, but are dominated by locally made materials that give chondrite groups their distinctive properties. Because of the large radial mixing in this scenario, it seems likely that most comets contain a similar mix of rocky materials. If this hypothesis is correct, then properties such as oxygen isotopes and minor element abundances in olivine, should have a wider dispersion than in any chondrite group, and this may be a characteristic property of primitive outer solar system bodies made from widely transported components.

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Section: Aqueous Alteration In Comets?mentioning

confidence: 99%

Overview of the rocky component of Wild 2 comet samples: Insight into the early solar system, relationship with meteoritic materials and the differences between comets and asteroids

Brownlee¹,

Joswiak

Matrajt

2012

Meteorit & Planetary Scien

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“…In order to compute the dose of radiation delivered to the liquid water stage of a comet by the decay of 26 Al, we must know the duration of every preceding stage and estimate the amount of radionuclide left at the beginning of the liquid stage, when chemical processes forming complex organic species may take place. To obtain the time evolution of the cometary body we follow the approach of Prialnik and Podolak [5], that makes use of the equation for energy balance (in 1 1…”

Section: Resultsmentioning

confidence: 99%

“…It was suggested that radiogenic heating with the consequent possible formation of liquid water in comet cores in the early solar system may have promoted chemical processes otherwise it is impossible in the frozen matrices of water and carbon monoxide ices [1]. The radionuclide 26 Al, that decays   to the stable 26 Mg with a decay constant 14 1 2.97 10 s      [2], is responsible for the delivery of the major portion of the energy to the newly formed cometary body.…”

Section: Introductionmentioning

confidence: 99%

The Effect of Radiogenic Heating on the Amino Acid Content of an Early Cometary Body

Canepa

2013

IJAA

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This study compares the rates for the formation and destruction of amino acids in the liquid cometary core subjected to radiogenic heating by the β⁺ decay of the cosmogenic nuclide ²⁶Al. The evolution of the temperature and mass of the comet were computed along with the dynamics of relatively complex organic species such as amino acids. Given the experimentally determined rate coefficient for the radiolysis of amino acids in water solution, the destruction of amino acids is virtually completed after an absorbed radiation dose of ~1 kGy. The calculations suggest that the liquid water core in comets with an initial radionuclide abundance that is sufficient to crystallize and melt the original amorphous ice is subjected to a dose of 100 - 1500 kGy. Any amino acid concentration formed in water either by radiolysis of simpler compounds or by thermal processes such as the synthesis of Strecker could not survive the irradiation delivered by the decay of ²⁶Al.

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“…Stratospheric collections of dust have already given us similar if smaller examples carbon rich particle clumps (Harris) [7]. The results of Schulz et al [30] are intriguing.…”

Section: Rosetta and Organic Materialsmentioning

confidence: 97%

“…We conceive of transient subsurface lakes arising from bolide impacts dissipating energy at depth, typically ~10-20 m in the 40 m craters near the Cheops Sea [7]. Chemoautotrophic microorganisms released from the ice into such 'lakes' laden with high-grade organics could undergo enough doublings to exhaust available nutrients within the observed eruption times of a couple of days.…”

Section: Introductionmentioning

confidence: 99%

Rosetta Studies of Comet 67P/Churyumov–Gerasimenko: Prospects for Establishing Cometary Biology

Nc¹,

Wainwright²,

Smith³

et al. 2015

Astrobiol Outreach

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We discuss a wide range of data emerging from the Rosetta Mission that all point indirectly to biological activity in Comet 67P/Churyumov-Gerasimenko. The existence of cracks and fissures on a smooth surface terrain apparently resealed, as well as early outgassing activity are consistent with the existence of subsurface lakes in which biological activity builds up high pressures of volatile gases that sporadically ruptures a frozen icy crust. While microorganisms probably require liquid water bodies for their early colonising of a comet, they can inhabit cracks in ice and sub-crustal snow, especially if they contain antifreeze salts and biopolymers. Some organisms metabolise at temperatures as low as 230 K, explaining the coma of Comet 97P out at 3.9AU and our prediction is that they would become increasingly active in the near-surface layers as the comet approaches its 1.3 AU perihelion. The detection of an overwhelming abundance of complex organic molecules at the surface by Philae and through IR imaging by the Rosetta orbiter is most significant.

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Liquid water and organics in Comets: implications for exobiology

Cited by 25 publications

References 19 publications

Overview of the rocky component of Wild 2 comet samples: Insight into the early solar system, relationship with meteoritic materials and the differences between comets and asteroids

Overview of the rocky component of Wild 2 comet samples: Insight into the early solar system, relationship with meteoritic materials and the differences between comets and asteroids

The Effect of Radiogenic Heating on the Amino Acid Content of an Early Cometary Body

Rosetta Studies of Comet 67P/Churyumov–Gerasimenko: Prospects for Establishing Cometary Biology

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