Large heterogeneities in comet 67P as revealed by active pits from sinkhole collapse

Pits have been observed on many cometary nuclei mapped by spacecraft(1-4). It has been argued that cometary pits are a signature of endogenic activity, rather than impact craters such as those on planetary and asteroid surfaces. Impact experiments(5,6) andmodels(7,8) cannot reproduce the shapes of most of the observed cometary pits, and the predicted collision rates imply that few of the pits are related to impacts(8,9). Alternative mechanisms like explosive activity(10) have been suggested, but the driving process remains unknown. Here we report that pits on comet 67P/Churyumov-Gerasimenko are active, and probably created by a sinkhole process, possibly accompanied by outbursts. We argue that after formation, pits expand slowly in diameter, owing to sublimation-driven retreat of the walls. Therefore, pits characterize how eroded the surface is: a fresh cometary surface will have a ragged structure with many pits, while an evolved surface will look smoother. The size and spatial distribution of pits imply that large heterogeneities exist in the physical, structural or compositional properties of the first few hundred metres below the current nucleus surface.

Sprache und Nationalität : Vortrag, gehalten in der Central-Vereins-Versammlung am 9. Dezember 1902

M. A. Klausner

Ludwig Frank, ein deutscher Jude

A. L.

Richard Kahle als Nathan der Weise [Illustration]

Scan von Monochrom-Mikroform

Johann Gottlieb von Bloch [Illustration] : russischer Staatsrat, gestorben Januar 1902

Scan von Monochrom-Mikroform

Grundakkorde jungjüdischer Kunst : (nach einer Ansprache zur Einführung in den jüdischen Kunstabend des Vereins jüdischer Studenten am 26. Februar 1902)

Theodor Zlocisti

Schlaflied für Mirjam : (Pan, Band IV, Heft 2)

Richard Beer-Hofmann

Verlags-Signet [Illustration] : (der Firma S. Calvary & Co. zum 50jährigen Jubiläum - Mai 1902 - von ihrem Personal gewidmet)

Hermann Struck

Sonnenstudie [Illustration]

Richard Goldberg-Leobschuetz

Studie zu einem Gemälde [Illustration]

Richard Goldberg-Leobschuetz

Betende Juden am großen Fasttage [Illustration]

Richard Goldberg-Leobschuetz

Gruppe aus dem Bilde "Betende Juden" [Illustration]

Richard Goldberg-Leobschuetz