Fates of satellite ejecta in the Saturn system

Alvarellos, J. L.; Zahnle, Kevin; Dobrovolskis, Anthony R.; Hamill, Patrick

doi:10.1016/j.icarus.2005.04.017

Cited by 43 publications

(62 citation statements)

References 31 publications

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“…In 2000-year-long simulations of ejecta escaping from Tethys, Alvarellos et al (2005; see also Dobrovolskis et al 2007) found that it takes between 650 and 1180 years to remove 99% of the test particles. Therefore at first we set the duration of our simulations of ejecta from Tethys' co-orbitals to the same 2000-yr limit.…”

Section: Fates Of Ejecta From the Coorbitalsmentioning

confidence: 98%

“…But because of three-body effects, a particle ejected from a moon may be considered to escape if it reaches the satellite's Hill sphere. The escape criterion then becomes V 0 ≥ V * e = γV e (Alvarellos et al 2002(Alvarellos et al , 2005, where the dimensionless correction factor…”

Section: The Dynamical Environmentmentioning

confidence: 99%

“…The actual ejection ring radii correspond to the mass median of each annulus. Then, given each ejection radius we compute the ejecta velocities according to the "rubble" model (Housen et al, 1983;Alvarellos et al, 2005). In the outer Solar System and in the Saturn system in particular, the most important impactors are the centaurs, formerly known as ecliptic comets (Shoemaker and Wolfe, 1982;Smith et al, 1982Smith et al, , 1986Zahnle et al, 1998).…”

Section: Ejecta From Coorbitals Produced By Centaur Impactsmentioning

confidence: 99%

“…In the outer Solar System and in the Saturn system in particular, the most important impactors are the centaurs, formerly known as ecliptic comets (Shoemaker and Wolfe, 1982;Smith et al, 1982Smith et al, , 1986Zahnle et al, 1998). For these objects, the impact speed U as obtained using Zahnle et al's (2001) Monte Carlo algorithm is given by U ≈ √ 3V orb (1 + 0.9 cos β) 0.35 (13) (Alvarellos et al 2005), where β is the impact site's angular distance to the apex of motion and V orb = na is the satellite's orbital speed; all else being equal, an impact at the apex point of a satellite occurs at a higher speed (and lower zenith angle) and hence produces a larger crater, which brings us to the topic of crater size. After the impact process itself is complete, a bowl-shaped depression called a transient crater is left at the target surface.…”

Section: Ejecta From Coorbitals Produced By Centaur Impactsmentioning

confidence: 99%

“…The ejection of debris takes place immediately after the impact. Loose material expected to be found at the surfaces of the low-gravity Trojans is assumed to be launched from the surface at an angle of 45 • from the vertical, at speeds (Housen et al, 1983); here x is the distance from the impact point, R t = D t /2 is the transient crater radius, and both K ≈ 0.57 and e x ≈ 1.770 are dimensionless constants (see Alvarellos et al 2005). The resulting ejection speeds range from 5 m/s to 30 m/s; launch speeds from the bigger Trojan Telesto are slightly higher than from Calypso, since V 0 scales as the square root of g. As before, these ejecta initial conditions are rotated and translated from the topocentric to the planetocentric coordinate system for ingestion into the integrator.…”

Section: Ejecta From Coorbitals Produced By Centaur Impactsmentioning

confidence: 99%

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Exchange of ejecta between Telesto and Calypso: Tadpoles, horseshoes, and passing orbits

Dobrovolskis

Alvarellos²,

Zahnle

et al. 2010

Icarus

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We have numerically integrated the orbits of ejecta from Telesto and Calypso, the two small Trojan companions of Saturn's major satellite Tethys. Ejecta were launched with speeds comparable to or exceeding their parent's escape velocity, consistent with impacts into regolith surfaces. We find that the fates of ejecta fall into several distinct categories, depending on both the speed and direction of launch.The slowest ejecta follow sub-orbital trajectories and re-impact their source moon in less than one day. Slightly faster debris barely escape their parent's Hill sphere and are confined to tadpole orbits, librating about Tethys' triangular Lagrange points L 4 (leading, near Telesto) or L 5 (trailing, near Calypso) with nearly the same orbital semi-major axis as Tethys, Telesto, and Calypso. These ejecta too eventually re-impact their source moon, but with a median lifetime of a few dozen years. Those which re-impact within the first ten years or so have lifetimes near integer multiples of 348.6 days (half the tadpole period).Still faster debris with azimuthal velocity components ∼ > 10 m/s enter horseshoe orbits which enclose both L 4 and L 5 as well as L 3 , but which avoid Tethys and its Hill sphere. These ejecta impact either Telesto or Calypso at comparable rates, with median lifetimes of several thousand years. However, they cannot reach Tethys itself; only the fastest ejecta, with azimuthal velocites ∼ > 40 m/s, achieve "passing orbits" which are able to encounter Tethys. Tethys accretes most of these ejecta within several years, but some 1% of them are scattered either inward to hit Enceladus or outward to strike Dione, over timescales on the order of a few hundred years.

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Section: Fates Of Ejecta From the Coorbitalsmentioning

confidence: 98%

Section: The Dynamical Environmentmentioning

confidence: 99%

Section: Ejecta From Coorbitals Produced By Centaur Impactsmentioning

confidence: 99%

Section: Ejecta From Coorbitals Produced By Centaur Impactsmentioning

confidence: 99%

Section: Ejecta From Coorbitals Produced By Centaur Impactsmentioning

confidence: 99%

See 3 more Smart Citations

Exchange of ejecta between Telesto and Calypso: Tadpoles, horseshoes, and passing orbits

Dobrovolskis

Alvarellos²,

Zahnle

et al. 2010

Icarus

Self Cite

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Differential impact cratering of Saturn's satellites by heliocentric impactors

Hirata

2016

J. Geophys. Res. Planets

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Saturnian satellites are thought to have been struck by two different types of impactors: those with heliocentric origins and those with planetocentric origins. Many of the impacts are suggested to come from planetocentric debris, while many crater count studies assume an ecliptic comet origin when determining the ages of the surfaces. To assess the contribution of planetocentric impactors, this study examines the global distribution and apex‐antapex asymmetry of impact craters on Rhea and Iapetus. The results demonstrate that the craters of Rhea (more than 20 km in diameter) and Iapetus (more than 30 km in diameter) show an apex‐antapex asymmetry. This suggests that most of the large craters are formed from heliocentric impacts. In contrast, the craters less than 20 km in diameter seem to show no asymmetry. Possible explanations for this are either planetocentric impactor origins or saturation with impact craters.

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