Origin of craters on Phoebe: comparison with Cassini ’s data

Rossignoli

2020

Celest Mech Dyn Astr

The current giant planet region is a transitional zone where transneptunian objects (TNOs) cross in their way to becoming Jupiter Family Comets (JFCs). Their dynamical behavior is conditioned by the intrinsic dynamical features of TNOs and also by the encounters with the giant planets. We address the Giant Planet Crossing (GPC) population (those objects with 5.2 au < q < 30 au) studying their number and their evolution from their sources, considering the current configuration of the Solar System. This subject is reviewed from previous investigations and also addressed by new numerical simulations of the dynamical evolution of Scattered Disk Objects (SDOs). We obtain a model of the intrinsic orbital element distribution of GPCs. The Scattered Disk represents the main source of prograde GPCs and Centaurs, while the contribution from Plutinos lies between one and two orders of magnitude below that from the SD. We obtain the number and size distribution of GPCs from our model, computing 9600 GPCs from the SD with D > 100 km and ∼ 10 8 with D > 1 km in the current population. The contribution from other sources is considered negligible. The mean lifetime in the Centaur zone is 7.2 Myr, while the mean lifetime of SDOs in the GPC zone is of 68 Myr. The latter is dependent on the initial inclination, being the ones with high inclinations the ones that survive the longest in the GPC zone. There is also a correlation of lifetime with perihelion distance, where greater perihelion leads to longer lifetime. The dynamical evolution of observed GPCs is different for prograde and retrograde objects. Retrograde GPCs have lower median lifetime than prograde ones, thus experiencing a comparatively faster evolution. However, it is probable that this faster evolution is due to the fact that the majority of retrograde GPCs have low perihelion values and then, lower lifetimes.

Section: Resultsmentioning

confidence: 99%

Centaur and giant planet crossing populations: origin and distribution

Rossignoli

2020

Celest Mech Dyn Astr

“…In order to evaluate the collisions of Centaurs on the small satellites of Saturn, we follow the method described in Di Sisto & Brunini (2011) and Di Sisto & Zanardi (2013). In those papers, the authors used the output files of the encounters of SDOs (those which are Centaurs) with Saturn, and, with a particle-in-abox approximation, calculated the number of collisions between Centaurs and the satellites.…”

Section: The Crater Production By Centaur Objectsmentioning

confidence: 99%

“…Di Sisto & Brunini (2011) and Di Sisto & Zanardi (2013) developed a theoretical model to calculate the cratering of a satellite due to impacts of Centaurs throughout the history of the solar system considering its current configuration. The Centaur population considered in those works is the one obtained as a byproduct of the dynamical evolution of SDOs through a numerical simulation done by Di Sisto & Brunini (2007).…”

Section: The Crater Production By Centaur Objectsmentioning

confidence: 99%

“…Di Sisto & Brunini (2011) and Di Sisto & Zanardi (2013) developed a theoretical model to calculate the cratering of the midsized Saturnian satellites produced by Centaur objects. The comparison between their theoretical production of craters, which is independent of the geological processes of a given surface, with the observed crater counts, which are highly affected by the geological history of the object, made it possible to estimate what is known as the "age" of the surface (Di Sisto & Zanardi 2016).…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Cratering and age of the small Saturnian satellites

Rossignoli

Zanardi

et al. 2019

A&A

Self Cite

Context. The small (≤ 135 km mean radius) satellites of Saturn are closely related to its rings and together they constitute a complex dynamical system where formation and destruction mechanisms compete against each other. The Cassini-Huygens mission provided high-resolution images of the surfaces of these satellites and therefore allowed for the calculation of observational crater counts. Aims. We model the cratering process by Centaur objects on the small Saturnian satellites, and compare our results with the observational crater counts obtained from the Voyager and Cassini missions. Methods. Using a theoretical model previously developed we calculate the crater production on these satellites considering two slopes of the size-frequency distribution (SFD) for the smaller objects of the Centaur population and compare our results with the available observations. In addition, we consider the case of catastrophic collisions between these satellites and Centaur objects and calculate the age of formation of those satellites that suffer one or more disruptions.Results. In general we find that the observed crater distributions are best modeled by the crater size distribution corresponding to the s 2 = 3.5 index of the SFD of impactors with diameters smaller than 60 km. However, for crater diameters D 3 − 8 km (which correspond to impactor diameters d ∼ 0.04 − 0.15 km), the observed distributions become flatter and deviate from our results, which may evidence processes of erosion and/or crater saturation at small crater sizes or a possible break in the SFD of impactors at d ∼ 0.04 − 0.15 km to a much shallower differential slope of ∼ −1.5. Our results suggest that Pan, Daphnis, Atlas, Aegaeon, Methone, Anthe, Pallene, Calypso, and Polydeuces suffered one or more catastrophic collisions over the age of the solar system, the younger being associated to arcs with ages of ∼ 10 8 years. We have also calculated surface ages for the satellites, which indicate ongoing resurfacing processes.

“…In a recent paper Di Sisto & Brunini (2011) (hereafter DB11) studied the craters on Phoebe produced by Centaurs from SDOs and plutinos. We use the same method described in that paper for each of the mid-sized Saturnian satellites.…”

Section: Introductionmentioning

confidence: 99%

The production of craters on the mid-sized saturnian satellites by Centaur objects

Zanardi

2013

A&A

Context. The Saturnian satellite system has been observed in detail by the Cassini-Huygens mission. These satellites present different surface features, including impact craters caused by small objects probably coming from the trans-Neptunian region. Aims. In this paper we calculate the production of craters on the mid-sized Saturnian satellites produced by Centaurs from the scattered disk (SD) and plutinos in order to determine this contribution, and we compare our estimations with the Cassini observations. Methods. We used a method developed in a previous paper that uses a numerical investigation of the dynamical evolution of Centaur objects to calculate the production of craters. We used a size-frequency distribution (SFD) of scattered disk objects (SDOs) as a power law with a break at diameters d = 60 km considering two cases for the differential power-law index: s 2 = 2.5 and s 2 = 3.5 for d < 60 km. Results. We calculated the number of craters, the greatest crater produced by Centaurs from the SD and plutinos, and the present cratering rate on each of the mid-sized satellites, for both cases of the SFD of SDOs considered. The contribution of plutinos is negligible compared to SDOs. From our calculations and the comparison with observations we note that the calculated number of craters for s 2 = 3.5 is in general nearer the observed number. However, in general for smaller craters, the observed number is less than the calculated one. This trend can be explained by at least two mechanisms. On the one hand, this could be caused by an erasing process that gradually buries the craters, which does not affect large craters. On the other hand, the comparison of the calculated and observed crater size-frequency distribution for different size ranges implies that for d < 60 km, the SFD of SDOs is consistent with the assumed index s 2 = 3.5, for d 0.2−1.4 km and for d 0.2−1.4 km, it is consistent with s 2 = 2.5. Then in the range d ∼ 0.2−1.4 km, the SFD of SDOs could have a new break. This change of slope could explain the reduction of small craters, at least for some cases. Conclusions. We found a good agreement when comparing our results with observations. However, independent determination of surface ages and geological processes are needed to determine if there is a new break on the SFD of SDOs, if there is a planetocentric source of craters in the Saturnian system, and which craters are primordial.