(50000) Quaoar: Surface composition variability

Abstract

Aims. The goal of this work is to investigate the composition of the surface of (50000) Quaoar and its spatial variability. Methods. We present new continuous spectra from the visible to near-IR (0.3−2.3 μm) obtained with the X-Shooter instrument at the VLT-ESO at four different epochs on the surface of Quaoar. The data represent the highest spectral resolution data ever obtained for this object and the first near-IR dataset acquired in a single exposure over the entire wavelength range. They are complemented by previously published photometric observations obtained in the near-IR (3.6, 4.5 μm) with the Spitzer Space Telescope, which provide an extra set of constraints in the model calculation. Spectral modelling was performed for the entire wavelength range by means of a code based on the Shkuratov radiative transfer formulation and of an updated value of albedo obtained from recent Herschel observations. Results. We obtained compositional information for different observed areas that can cover about 40% of the assumed rotational period of 8.84 h. Our analysis helps to prove the presence of CH 4 and C 2 H 6 , as previously reported, along with indications of the possible presence of NH 3 ·H 2 O. New evidence of N 2 is inferred from the shift in the CH 4 bands. The albedo at the two Spitzer bands suggests there may be CO diluted in N 2 , and CO 2 for one of the surface locations. Conclusions. The spectral similarities indicate the overall homogeneity of the surface composition of one hemisphere of Quaoar, while some subtle variations are apparent when modelling. The presence of NH 3 ·H 2 O would support the idea that Quaoar's surface may be relatively young.

Physical state and distribution of materials at the surface of Pluto from New Horizons LEISA imaging spectrometer

“…This identification is not firm because most of the absorption bands of ethane ice are located in spectral regions dominated by CH 4 absorption and the observed features are weak Sasaki et al, 2005;Cruikshank et al, 2006;DeMeo et al, 2010;Merlin et al, 2010;Holler et al, 2014 ). It should be noted that C 2 H 6 has also been tentatively identified on the KBO 50,0 0 0 Quaoar ( Dalle Ore et al, 2009;Barucci et al, 2015 ). Species expected to arise from N 2 :CH 4 photochemistry, such as C 2 H 2 , C 4 H 2 , HC 3 N and HCN, have not been detected.…”

Optimal Trajectories to Kuiper Belt Objects

“…This fact can be an indication that other KBOs with sizes comparable to Pluto could also present recent geological activity. One example of this possibility is the potential presence of cryovolcanism in Quaoar (Barucci et al 2015). However, due to the large distance of the KBOs from the Sun, observational data were not enough to significantly improve our knowledge about these bodies, to carry out comparative planetology.…”

Kuiper Belt

“…The rotational period is approximately 8.84 h, and it has one known satellite (Weywot, about 80 km in size). The best compositional model obtained so far (Barucci et al 2015) reported a surface made of crystalline water ice, methane, as well as ethane, nitrogen, organic materials, and possibly ammonia water. The presence of high volatile material such as ammonia water and nitrogen suggests that the surface of Quaoar may be relatively young and shaped by an efficient renewal mechanism.…”