Gravitational slopes, geomorphology, and material strengths of the nucleus of comet 67P/Churyumov-Gerasimenko from OSIRIS observations

Abstract

We study the link between gravitational slopes and the surface morphology on the nucleus of comet 67P/Churyumov-Gerasimenko and provide constraints on the mechanical properties of the cometary material. We computed the gravitational slopes for five regions on the nucleus that are representative of the different morphologies observed on the surface, using two shape models computed from OSIRIS images by the stereo-photoclinometry (SPC) and stereo-photogrammetry (SPG) techniques. We estimated the tensile, shear, and compressive strengths using different surface morphologies and mechanical considerations. The different regions show a similar general pattern in terms of the relation between gravitational slopes and terrain morphology: i) low-slope terrains (0-20 deg) are covered by a fine material and contain a few large ($>$10 m) and isolated boulders, ii) intermediate-slope terrains (20-45 deg) are mainly fallen consolidated materials and debris fields, with numerous intermediate-size boulders from $<$1 m to 10 m for the majority of them, and iii) high-slope terrains (45-90 deg) are cliffs that expose a consolidated material and do not show boulders or fine materials. The best range for the tensile strength of overhangs is 3-15 Pa (upper limit of 150 Pa), 4-30 Pa for the shear strength of fine surface materials and boulders, and 30-150 Pa for the compressive strength of overhangs (upper limit of 1500 Pa). The strength-to-gravity ratio is similar for 67P and weak rocks on Earth. As a result of the low compressive strength, the interior of the nucleus may have been compressed sufficiently to initiate diagenesis, which could have contributed to the formation of layers. Our value for the tensile strength is comparable to that of dust aggregates formed by gravitational instability and tends to favor a formation of comets by the accrection of pebbles at low velocities.

18 pages, 15 figures, 1 table; Astronomy and Astrophysics, in press

References in corpus (3)

• Comets formed in solar-nebula instabilities! -- An experimental and modeling attempt to relate the activity of comets to their formation process (corrigendum included)
• The Physics of Protoplanetesimal Dust Agglomerates. IV. Towards a Dynamical Collision Model
• What drives the dust activity of comet 67P/Churyumov-Gerasimenko?

Cited by in corpus (35)

• Evidence for the formation of comet 67P/Churyumov-Gerasimenko through gravitational collapse of a bound clump of pebbles
• Synthesis of the Morphological Description of Cometary Dust at Comet 67P
• Summer fireworks on comet 67P
• Are fractured cliffs the source of cometary dust jets ? Insights from OSIRIS/Rosetta at 67P
• Spectroscopy and thermal modelling of the first interstellar object 1I/2017 U1 'Oumuamua
• The Rosetta mission orbiter Science overview the comet phase
• The thermal, mechanical, structural, and dielectric properties of cometary nuclei after Rosetta
• Temporal morphological changes in the Imhotep region of comet 67P/Churyumov-Gerasimenko
• Rotation of Cometary Nuclei: New Lightcurves and an Update of the Ensemble Properties of Jupiter-Family Comets
• Unveiling Dust Aggregate Structure in Protoplanetary Disks by Millimeter-wave Scattering Polarization
• Evidence of sub-surface energy storage in comet 67P from the outburst of 2016 July 3
• Comet 67P/Churyumov-Gerasimenko: Constraints on its origin from OSIRIS observations
• Tensile Strength of 67P/Churyumov-Gerasimenko Nucleus Material from Overhangs
• Tensile Strength of Porous Dust Aggregates
• Constraints on cometary surface evolution derived from a statistical analysis of 67P's topography
• The tensile strength of dust aggregates consisting of small elastic grains: Constraints on the size of condensates in protoplanetary disks
• Rotationally Induced Surface Slope-Instabilities and the Activation of CO2 Activity on Comet 103P/Hartley 2
• Thermal fracturing on comets. Applications to 67P/Churyumov-Gerasimenko
• The Sublimative Torques of Jupiter Family Comets and Mass Wasting Events on Their Nuclei
• Local manifestations of cometary activity
• Why are Jupiter-family comets active and asteroids in cometary-like orbits inactive?
• Experiments on cometary activity: ejection of dust aggregates from a sublimating water-ice surface
• Thermal inertias of pebble-pile comet 67P/Churyumov-Gerasimenko
• White dwarf planetary debris dependence on physical structure distributions within asteroid belts
• Cometary dust analogues for physics experiments
• New Insights into Interstellar Object 1I/2017 U1 (`Oumuamua) from SOHO/STEREO Nondetections
• CO2-driven surface changes in the Hapi region on Comet 67P/Churyumov-Gerasimenko
• Analog Experiments on Tensile Strength of Dusty and Cometary Matter
• Cliff collapse on Comet 67P/Churyumov-Gerasimenko -- I. Aswan
• Dynamics and potential origins of decimeter-sized particles around comet 67P/Churyumov-Gerasimenko
• Ancient and present surface evolution processes in the Ash regionof comet 67P/Churyumov-Gerasimenko
• Studying the nucleus of comet 9P/Tempel 1 using the structure of the Deep Impact ejecta cloud at the early stages of its development
• Collisional heating of icy planetesimals. I. Catastrophic collisions
• Dynamics and Origin of Comets: New Problems Appeared after the Rosetta Space Mission
• Enlargement of depressions on comet 81P/Wild 2: Constraint based on 30-year cometary activity in the inner Solar System