On Mercury’s past rotation, in light of its large craters

Research output: Contribution to JournalArticleAcademicpeer-review

Abstract

We have simulated in-orbit variations of the impact flux and spatial distributions of >100 km diameter (D) crater production for Mercury in its current 3:2 and hypothetical 2:1 and 1:1 spin–orbit resonances. Results show that impact fluxes and D > 100 km cratering are non-uniform for these rotational states when Mercury's orbit is significantly eccentric. Variations in the impact flux and D > 100 km cratering depend on the orbital elements of Mercury and its impactors. The observed spatial distribution of large Mercurian craters is difficult to generate by cratering in Mercury's current 3:2 spin–orbit resonance, but can be produced by cratering in a former 1:1 (as previously proposed by Wieczorek et al., 2012) or 2:1 spin–orbit resonance. We have calculated capture probabilities at spin–orbit resonances for a rigid Mercury. If Mercury's initial rotation was prograde, we find that a higher order spin–orbit resonance is the most likely first capture for feasible (low) values of Mercury's past triaxiality. In light of Mercury's crater record, we examined the possibility that impacts have initiated transitions in past spin–orbit resonances. Although the number of craters whose generating impact would have destabilized a spin–orbit resonance is sensitive to the crater scaling procedure, any initial rotational state of Mercury has likely been destabilized by impacts. An initial and permanent 3:2 spin–orbit resonance capture seems untenable. Mercury's tidal torque decelerates Mercury's rotation for the most likely range of Mercury's orbital eccentricity. Only one or two craters are candidate relics of an impact-event that facilitates an instantaneous transition from a former synchronous rotation to the 3:2 spin–orbit resonance, and only for a small crater scaling factor. We propose a rotational evolution trajectory for Mercury with visits to spin–orbit resonances of decreasing order including a substantial period in the 2:1 spin–orbit resonance, which can account for the observed spatial distribution of large craters.
LanguageEnglish
Pages1-18
JournalIcarus
Issue number281
DOIs
Publication statusPublished - 1 Jan 2017

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craters
crater
orbits
cratering
spatial distribution
rotational states
mercury
scaling
triaxial stresses
impactors
orbital elements
eccentrics
eccentricity
torque
trajectory
trajectories
orbitals

Cite this

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title = "On Mercury’s past rotation, in light of its large craters",
abstract = "We have simulated in-orbit variations of the impact flux and spatial distributions of >100 km diameter (D) crater production for Mercury in its current 3:2 and hypothetical 2:1 and 1:1 spin–orbit resonances. Results show that impact fluxes and D > 100 km cratering are non-uniform for these rotational states when Mercury's orbit is significantly eccentric. Variations in the impact flux and D > 100 km cratering depend on the orbital elements of Mercury and its impactors. The observed spatial distribution of large Mercurian craters is difficult to generate by cratering in Mercury's current 3:2 spin–orbit resonance, but can be produced by cratering in a former 1:1 (as previously proposed by Wieczorek et al., 2012) or 2:1 spin–orbit resonance. We have calculated capture probabilities at spin–orbit resonances for a rigid Mercury. If Mercury's initial rotation was prograde, we find that a higher order spin–orbit resonance is the most likely first capture for feasible (low) values of Mercury's past triaxiality. In light of Mercury's crater record, we examined the possibility that impacts have initiated transitions in past spin–orbit resonances. Although the number of craters whose generating impact would have destabilized a spin–orbit resonance is sensitive to the crater scaling procedure, any initial rotational state of Mercury has likely been destabilized by impacts. An initial and permanent 3:2 spin–orbit resonance capture seems untenable. Mercury's tidal torque decelerates Mercury's rotation for the most likely range of Mercury's orbital eccentricity. Only one or two craters are candidate relics of an impact-event that facilitates an instantaneous transition from a former synchronous rotation to the 3:2 spin–orbit resonance, and only for a small crater scaling factor. We propose a rotational evolution trajectory for Mercury with visits to spin–orbit resonances of decreasing order including a substantial period in the 2:1 spin–orbit resonance, which can account for the observed spatial distribution of large craters.",
author = "J.S. Knibbe and {van Westrenen}, W.",
year = "2017",
month = "1",
day = "1",
doi = "10.1016/j.icarus.2016.08.036",
language = "English",
pages = "1--18",
journal = "Icarus",
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}

On Mercury’s past rotation, in light of its large craters. / Knibbe, J.S.; van Westrenen, W.

In: Icarus, No. 281, 01.01.2017, p. 1-18.

Research output: Contribution to JournalArticleAcademicpeer-review

TY - JOUR

T1 - On Mercury’s past rotation, in light of its large craters

AU - Knibbe, J.S.

AU - van Westrenen, W.

PY - 2017/1/1

Y1 - 2017/1/1

N2 - We have simulated in-orbit variations of the impact flux and spatial distributions of >100 km diameter (D) crater production for Mercury in its current 3:2 and hypothetical 2:1 and 1:1 spin–orbit resonances. Results show that impact fluxes and D > 100 km cratering are non-uniform for these rotational states when Mercury's orbit is significantly eccentric. Variations in the impact flux and D > 100 km cratering depend on the orbital elements of Mercury and its impactors. The observed spatial distribution of large Mercurian craters is difficult to generate by cratering in Mercury's current 3:2 spin–orbit resonance, but can be produced by cratering in a former 1:1 (as previously proposed by Wieczorek et al., 2012) or 2:1 spin–orbit resonance. We have calculated capture probabilities at spin–orbit resonances for a rigid Mercury. If Mercury's initial rotation was prograde, we find that a higher order spin–orbit resonance is the most likely first capture for feasible (low) values of Mercury's past triaxiality. In light of Mercury's crater record, we examined the possibility that impacts have initiated transitions in past spin–orbit resonances. Although the number of craters whose generating impact would have destabilized a spin–orbit resonance is sensitive to the crater scaling procedure, any initial rotational state of Mercury has likely been destabilized by impacts. An initial and permanent 3:2 spin–orbit resonance capture seems untenable. Mercury's tidal torque decelerates Mercury's rotation for the most likely range of Mercury's orbital eccentricity. Only one or two craters are candidate relics of an impact-event that facilitates an instantaneous transition from a former synchronous rotation to the 3:2 spin–orbit resonance, and only for a small crater scaling factor. We propose a rotational evolution trajectory for Mercury with visits to spin–orbit resonances of decreasing order including a substantial period in the 2:1 spin–orbit resonance, which can account for the observed spatial distribution of large craters.

AB - We have simulated in-orbit variations of the impact flux and spatial distributions of >100 km diameter (D) crater production for Mercury in its current 3:2 and hypothetical 2:1 and 1:1 spin–orbit resonances. Results show that impact fluxes and D > 100 km cratering are non-uniform for these rotational states when Mercury's orbit is significantly eccentric. Variations in the impact flux and D > 100 km cratering depend on the orbital elements of Mercury and its impactors. The observed spatial distribution of large Mercurian craters is difficult to generate by cratering in Mercury's current 3:2 spin–orbit resonance, but can be produced by cratering in a former 1:1 (as previously proposed by Wieczorek et al., 2012) or 2:1 spin–orbit resonance. We have calculated capture probabilities at spin–orbit resonances for a rigid Mercury. If Mercury's initial rotation was prograde, we find that a higher order spin–orbit resonance is the most likely first capture for feasible (low) values of Mercury's past triaxiality. In light of Mercury's crater record, we examined the possibility that impacts have initiated transitions in past spin–orbit resonances. Although the number of craters whose generating impact would have destabilized a spin–orbit resonance is sensitive to the crater scaling procedure, any initial rotational state of Mercury has likely been destabilized by impacts. An initial and permanent 3:2 spin–orbit resonance capture seems untenable. Mercury's tidal torque decelerates Mercury's rotation for the most likely range of Mercury's orbital eccentricity. Only one or two craters are candidate relics of an impact-event that facilitates an instantaneous transition from a former synchronous rotation to the 3:2 spin–orbit resonance, and only for a small crater scaling factor. We propose a rotational evolution trajectory for Mercury with visits to spin–orbit resonances of decreasing order including a substantial period in the 2:1 spin–orbit resonance, which can account for the observed spatial distribution of large craters.

U2 - 10.1016/j.icarus.2016.08.036

DO - 10.1016/j.icarus.2016.08.036

M3 - Article

SP - 1

EP - 18

JO - Icarus

T2 - Icarus

JF - Icarus

SN - 0019-1035

IS - 281

ER -