Physical and dynamical characterization of the Euphrosyne asteroid family

Abstract

Aims. The Euphrosyne asteroid family occupies a unique zone in orbital element space around 3.15 au and may be an important source of the low-albedo near-Earth objects. The parent body of this family may have been one of the planetesimals that delivered water and organic materials onto the growing terrestrial planets. We aim to characterize the compositional properties as well as the dynamical properties of the family. Methods. We performed a systematic study to characterize the physical properties of the Euphrosyne family members via low-resolution spectroscopy using the NASA Infrared Telescope Facility. In addition, we performed smoothed-particle hydrodynamics (SPH) simulations and N-body simulations to investigate the collisional origin, determine a realistic velocity field, study the orbital evolution, and constrain the age of the Euphrosyne family. Results. Our spectroscopy survey shows that the family members exhibit a tight taxonomic distribution, suggesting a homogeneous composition of the parent body. Our SPH simulations are consistent with the Euphrosyne family having formed via a reaccumulation process instead of a cratering event. Finally, our N-body simulations indicate that the age of the family is 280−80+180 Myr, which is younger than previous estimates.

VLT/SPHERE imaging survey of the largest main-belt asteroids: Final results and synthesis

“…-Large (D ≥ 130 km) P-types likely partially differentiated (Pajuelo et al 2018;Carry et al 2021) and their interior (core) may not simply have a C-type-like density (typically 1.7 g cm −3 ; Carry et al 2021) but also C-type spectral properties as suggested by the spectroscopic observations of the Eurybates family (Fornasier et al 2007;De Luise et al 2010). We note that spectroscopic observations of two large C-type families in the outer belt (Themis, Euphrosyne) show a mix of C-and P-types bodies, and therefore a similar spectral heterogeneity as observed in the case of the Eurybates family (Marsset et al 2016;Yang et al 2020a). -The compositional (spectral type) mass distribution throughout the asteroid belt shows a rather sharp transition from the C-to the P-types (DeMeo & Carry 2013, 2014 and Fig.…”

“…This implies that their present outer shell has witnessed aqueous alteration. Furthermore, visible and NIR spectroscopic observations of two major C-type collisional families (Themis and Euphrosyne; Marsset et al 2016;Yang et al 2020a) indicate some degree of spectral variation (from C to P/X) that may hint at a primordial heterogeneous internal structure of their parent bodies (Marsset et al 2016).…”

Asteroid Families: properties, recent advances and future opportunities

“…Let us, however, discuss one striking example that suggests even more caution is needed when interpreting family ages. Yang et al (2020b) recently analysed (31) Euphrosyne family and found an age of 280 +180 −80 Myr. It is significantly younger than the estimate of 1230 ± 410 Myr coming from Spoto et al (2015).…”

“…Previously, the age of the family was also estimated to ∼ 500 Myr, by modelling population of family members interacting with the ν 6 secular resonance (Carruba et al, 2014). Though in principle, one may expect those age estimations based on the evolution caused by gravitational interactions used by Yang et al (2020b) and Carruba et al (2014) could somewhat underestimate the age, the differences are still immense and raise a warning.…”

“…A potentially significant reservoir of MBCs could also be the Euphrosyne asteroid family, yet another group of primitive C-type asteroids in the outer main belt (Yang et al, 2020b). The recent work by Yang et al (2020a) suggested that the largest family member, asteroid (31) Euphrosyne, probably contains a significant fraction of water ice in its interior.…”