The refractory-to-ice mass ratio in comets

Fulle, M.; Blum, Jürgen; Green, Simon; Gundlach, Bastian; Hérique, Alain; Moreno, Fernando; Mottola, S.; Rotundi, A.; Snodgrass, C.

doi:10.1093/mnras/sty2926

Cited by 76 publications

(84 citation statements)

References 102 publications

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“…Landslides on 67P reveal a clear rocky‐type behavior for cometary material that, once collapsed, assumes a rock avalanche mobilization associated to relatively high friction coefficients. This behavior agrees with the refractory to ice ratio estimated from grains ejected from 67P (Fulle et al, ). In addition, the considerable variability of H/L values among the different landslides suggests that different volatile contents of the detached mass play a fundamental role on the gravitational process and final runout, hence being a general indicator for the subsurface cometary heterogeneities.…”

Section: Resultssupporting

confidence: 90%

The Rocky‐Like Behavior of Cometary Landslides on 67P/Churyumov‐Gerasimenko

Lucchetti

Penasa

Pajola

et al. 2019

Geophysical Research Letters

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Landslides have been identified on several solar system bodies, and different mechanisms have been proposed to explain their runout length. We analyze images from the Rosetta mission and report the global characterization of such features on comet 67P/Churyumov-Gerasimenko's surface. By assuming the height to runout length as an approximation for the friction coefficient of landslide material, we find that on comet 67P, this ratio falls between 0.50 and 0.97. Such unexpected high values reveal a rocky-type mechanical behavior that is much more akin to Earth dry landslides than to icy satellites' mass movements. This behavior indicates that 67P and likely comets in general are characterized by consolidated materials possibly rejecting the idea that they are fluffy aggregates. The variability of the runout length among 67P landslides can be attributed to the different volatile content located in the top few meters of the cometary crust, which can drive the mass movement.

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Section: Resultssupporting

confidence: 90%

The Rocky‐Like Behavior of Cometary Landslides on 67P/Churyumov‐Gerasimenko

Lucchetti

Penasa

Pajola

et al. 2019

Geophysical Research Letters

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“…Ma'at), are almost entirely cleaned-up in consolidated regions, exposing the underlying consolidated material. This is consistent with the idea of "self-cleaning" of the Northern hemisphere proposed by Fulle et al (2019). (c) and (d) could quench dust activity in fallback regions, but do not play a role in consolidated areas.…”

Section: Discussionsupporting

confidence: 91%

Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta

Tubiana

Rinaldi

Güttler

et al. 2019

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Context. On 27 April 2015, when 67P/Churyumov-Gerasimenko was at 1.76 au from the Sun and moving towards perihelion, the OSIRIS and VIRTIS-M instruments on board Rosetta simultaneously observed the evolving dust and gas coma during a complete rotation of the comet. Aims. We aim to characterize the dust, H 2 O and CO 2 gas spatial distribution in the inner coma. To do this we performed a quantitative analysis of the release of dust and gas and compared the observed H 2 O production rate with the one calculated using a thermo-physical model. Methods. For this study we selected OSIRIS WAC images at 612 nm (dust) and VIRTIS-M image cubes at 612 nm, 2700 nm (H 2 O emission band) and 4200 nm (CO 2 emission band). We measured the average signal in a circular annulus, to study spatial variation around the comet, and in a sector of the annulus, to study temporal variation in the sunward direction with comet rotation, both at a fixed distance of 3.1 km from the comet centre.Results. The spatial correlation between dust and water, both coming from the sun-lit side of the comet, shows that water is the main driver of dust activity in this time period. The spatial distribution of CO 2 is not correlated with water and dust. There is no strong temporal correlation between the dust brightness and water production rate as the comet rotates. The dust brightness shows a peak at 0 • sub-solar longitude, which is not pronounced in the water production. At the same epoch, there is also a maximum in CO 2 production. An excess of measured water production, with respect to the value calculated using a simple thermo-physical model, is observed when the head lobe and regions of the Southern hemisphere with strong seasonal variations are illuminated (sub-solar longitude 270 • -50 • ). A drastic decrease in dust production, when the water production (both measured and from the model) displays a maximum, happens when typical Northern consolidated regions are illuminated and the Southern hemisphere regions with strong seasonal variations are instead in shadow (sub-solar longitude 50 • -90 • ). Possible explanations of these observations are presented and discussed.

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“…Even higher D/I ratios (cf. Fulle et al (2018)), which would be associated with a higher percentage of backfall of dry dust, can easily be derived from the numbers given in Table 4. The most prominent differences when changing the D/I ratio are expected in the H/Si and O/Si ratios, given that water is the main component in the cometary ices.…”

Section: Discussionmentioning

confidence: 99%

Elemental and molecular abundances in comet 67P/Churyumov-Gerasimenko

Rubin

Altwegg

Balsiger

et al. 2019

Monthly Notices of the Royal Astronomical Society

156

189

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Comets are considered to be some of the most pristine and unprocessed solar system objects accessible to in-situ exploration. Investigating their molecular and elemental composition takes us on a journey back to the early period of our solar system and possibly even further. In this work, we deduce the bulk abundances of the major volatile species in comet 67P/Churyumov-Gerasimenko, the target of the European Space Agency's Rosetta mission. The basis are measurements obtained with the ROSINA instrument suite on board the Rosetta orbiter during a suitable period of high outgassing near perihelion. The results are combined with both gas and dust composition measurements published in the literature. This provides an integrated inventory of the major elements present in the nucleus of 67P/Churyumov-Gerasimenko. Similar to comet 1P/Halley, which was visited by ESA's Giotto spacecraft in 1986, comet 67P/Churyumov-Gerasimenko also shows near-solar abundances of oxygen and carbon, whereas hydrogen and nitrogen are depleted compared to solar. Still, the degree of devolatilization is lower than that of inner solar system objects, * E-mail: martin.rubin@space.unibe.ch 2 including meteorites and the Earth. This supports the idea that comets are among the most pristine objects in our solar system.

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The refractory-to-ice mass ratio in comets

Cited by 76 publications

References 102 publications

The Rocky‐Like Behavior of Cometary Landslides on 67P/Churyumov‐Gerasimenko

The Rocky‐Like Behavior of Cometary Landslides on 67P/Churyumov‐Gerasimenko

Diurnal variation of dust and gas production in comet 67P/Churyumov-Gerasimenko at the inbound equinox as seen by OSIRIS and VIRTIS-M on board Rosetta

Elemental and molecular abundances in comet 67P/Churyumov-Gerasimenko

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