Europa’s Crater Distributions and Surface Ages

Bierhaus, E. B.; Zahnle, K.; Chapman, C. R.

doi:10.2307/j.ctt1xp3wdw.13

Cited by 65 publications

(89 citation statements)

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“…If the input of amino acids continues for 50 million years [a typical surface age based on the size distribution analysis of impact craters by Bierhaus et al, (2009)], the overall delivery of cometary amino acids is 5 · 10 9 kg. If this input is distributed evenly on Europa's surface and is mixed homogenously with a depth of 1 m of the ice shell [an average gardening depth of 10 million years old (Carlson et al, 2009)], the resultant surface concentration of amino acids is around 0.1 ppm.…”

Section: Discussionmentioning

confidence: 99%

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Polymerization of Building Blocks of Life on Europa and Other Icy Moons

Kimura

Kitadai

2015

Astrobiology

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The outer Solar System may provide a potential habitat for extraterrestrial life. Remote sensing data from the Galileo spacecraft suggest that the jovian icy moons-Europa, Ganymede, and possibly Callisto-may harbor liquid water oceans underneath their icy crusts. Although compositional information required for the discussion of habitability is limited because of significantly restricted observation data, organic molecules are ubiquitous in the Universe. Recently, in situ spacecraft measurements and experiments suggest that amino acids can be formed abiotically on interstellar ices and comets. These amino acids could be continuously delivered by meteorite or comet impacts to icy moons. Here, we show that polymerization of organic monomers, in particular amino acids and nucleotides, could proceed spontaneously in the cold environment of icy moons, in particular the jovian icy moon Europa as a typical example, based on thermodynamic calculations, though kinetics of formation are not addressed. Observed surface temperature on Europa is 120 and 80 K in the equatorial region and polar region, respectively. At such low temperatures, Gibbs energies of polymerization become negative, and the estimated thermal structure of the icy crust should contain a shallow region (i.e., at a depth of only a few kilometers) favorable for polymerization. Investigation of the possibility of organic monomer polymerization on icy moons could provide good constraints on the origin and early evolution of extraterrestrial life.

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Section: Discussionmentioning

confidence: 99%

“…There are few impact craters because its surface is tectonically active and young. Based on estimates of the frequency of cometary bombardment that Europa is likely to endure, the surface is approximately 20-200 million years old (Bierhaus et al, 2009). The surface is, however, covered by many tectonic features.…”

Section: Environment Of Europamentioning

confidence: 99%

Polymerization of Building Blocks of Life on Europa and Other Icy Moons

Kimura

Kitadai

2015

Astrobiology

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“…Both suffered most collisions during the dispersal of the primitive disk (or before, if the dispersal was late). It is true that comets have a shallower distribution (Snodgrass et al 2011) as well as have the craters on the Jovian satellites (Bierhaus 2006;Bierhaus et al 2009). But this is probably because small comets disintegrate very quickly.…”

Section: Dynamical Modelmentioning

confidence: 99%

How primordial is the structure of comet 67P?

Jutzi

Benz

Τόλιου

et al. 2016

A&A

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Context. There is an active debate about whether the properties of comets as observed today are primordial or, alternatively, if they are a result of collisional evolution or other processes. Aims. We investigate the effects of collisions on a comet with a structure like 67P/Churyumov-Gerasimenko (67P). We develop scaling laws for the critical specific impact energies Q reshape required for a significant shape alteration. These are then used in simulations of the combined dynamical and collisional evolution of comets in order to study the survival probability of a primordially formed object with a shape like 67P. Although the focus of this work is on a structure of this kind, the analysis is also performed for more generic bi-lobe shapes, for which we define the critical specific energy Q bil . The simulation outcomes are also analyzed in terms of impact heating and the evolution of the porosity. Methods. The effects of impacts on comet 67P are studied using a state-of-the-art smooth particle hydrodynamics shock physics code. In the 3D simulations, a publicly available shape model of 67P is applied and a range of impact conditions and material properties are investigated. The resulting critical specific impact energy Q reshape (as well as Q bil for generic bi-lobe shapes) defines a minimal projectile size which is used to compute the number of shape-changing collisions in a set of dynamical simulations. These simulations follow the dispersion of the trans-Neptunian disk during the giant planet instability, the formation of a scattered disk, and produce 87 objects that penetrate into the inner solar system with orbits consistent with the observed JFC population. The collisional evolution before the giant planet instability is not considered here. Hence, our study is conservative in its estimation of the number of collisions. Results. We find that in any scenario considered here, comet 67P would have experienced a significant number of shape-changing collisions, if it formed primordially. This is also the case for generic bi-lobe shapes. Our study also shows that impact heating is very localized and that collisionally processed bodies can still have a high porosity. Conclusions. Our study indicates that the observed bi-lobe structure of comet 67P may not be primordial, but might have originated in a rather recent event, possibly within the last 1 Gy. This may be the case for any kilometer-sized two-component cometary nuclei.

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“…The total number of primary impact craters on Europa is small (Moore et al, 1998;Schenk, 2002;Bierhaus et al, 2009), which implies a relatively high intensity of endogenous resurfacing on this planet. Estimates of the age of the surface, however, strongly depend on the models of the flux of cratering bodies.…”

Section: Introductionmentioning

confidence: 99%