Estimating the density of intermediate size KBOs from considerations of volatile retention

Abstract

By using a hydrodynamic atmospheric escape mechanism (Levi and Podolak, 2009) we show how the unusually high mass density of Quaoar could have been predicted (constrained), without any knowledge of a binary companion. We suggest an explanation of the recent spectroscopic observations of Orcus and Charon Cook et al., 2007). We present a simple relation between the detection of certain volatile ices and the body mass density and diameter. As a test case we implement the relations on the KBO 2003 AZ 84 and give constraints on its mass density. We also present a method of relating the latitude-dependence of hydrodynamic gas escape to the internal structure of a rapidly rotating body and apply it to Haumea. Key Words: ICES; KUIPER BELT; TRANS-NEPTUNIAN OBJECTS 9 θ [ pi ] escape criterion Colatitude extent of escape ( T surf =150 [K] ) J 2 =0.05 J 2 =0.10 J 2 =0.20 J 2 =0.05 J 2 =0.10 J 2 =0.20Figure 3: Levi and Podolak, Estimating KBO densities T 0 [k] surface fraction surface fraction evacuated V. surface temperature J 2 =0.05 (800km) J 2 =0.10 (800km) J 2 =0.20 (800km) J 2 =0.05 (880km) J 2 =0.10 (880km) J 2 =0.20 (880km) Figure 5: Levi and Podolak, Estimating KBO densities

THERMAL ESCAPE IN THE HYDRODYNAMIC REGIME: RECONSIDERATION OF PARKER's ISENTROPIC THEORY BASED ON RESULTS OF KINETIC SIMULATIONS

“…This is a result of the non-equilibrium nature of the flow in the Knudsen layer, where both enthalpy and entropy substantially change, so that the parameters at the bottom of the isentropic flow zone always differ from parameters at the source surface. These results are directly applicable to recent efforts (e.g., Stern & Trafton 2008;Levi & Podolak 2009, 2011 to model sublimation-driven atmospheres on KBO-like objects, for which the EUV heating is often insignificant. If there is significant heating in the simulation region that overwhelms the changes in the enthalpy, then a hydrodynamic model starting at the source surface can in principle give a reasonable description of the flow structure.…”

“…For these conditions, the surface vapor pressure varies from ∼10 −8 Pa for CH 4 to ∼10 −3 Pa for N 2 (Stern & Trafton 2008), which roughly corresponds to the mean free path of gas molecules l 0 ranging from 10 5 m to 1 m, or to the range of Knudsen number, Kn 0 = l 0 /R 0 , from 1 to 10 −5 , which is fully considered in the present paper. The differences between our simulations and previous attempts to describe the KBO atmospheres based on Parker's theory (Levi & Podolak 2009, 2011 are highlighted in Section 3.…”

“…This paper focuses on the consideration of the thermally induced, hydrodynamic escape regime. In the solar system, such flows are characteristic for outflows from surfaces of objects with low gravity such as comet nuclei (Crifo et al 2002;Tenishev et al 2008), early terrestrial atmospheres (Watson et al 1981;Zahnle & Kasting 1986;Hunten et al 1987), and atmospheres of the Kuiper belt objects (KBOs; Stern & Trafton 2008;Levi & Podolak 2009, 2011. The aeronomy of the extrasolar planets, in principle, appears to provide large variety of hydrodynamically escaping outflows, since stellar radiation can induce a transition to blow-off even in atmospheres on massive Jupiter-type exoplanets.…”

A portrait of the extreme solar system object 2012 DR30

“…We note that the stability of 2012 DR 30 does not vary significantly as a function of the initial eccentricity or inclination and perihelion distance used, a reflection of the relatively high precision with which the objects orbit is known. escape rate of methane is so large that 2012 DR 30 certainly cannot retain this molecule on the surface even for a few thousand years, considering either Jeans or hydrodynamic escape rates (Schaller & Brown 2007;Levi & Podolak 2011). Replenishment of methane from subsurface resources is indeed a possibility, however, no cometary activity has been observed so far which otherwise would support this scenario.…”

Irradiation of nitrogen-rich ices by swift heavy ions

“…in which up to several tens of percent of N have been incorporated and with low amounts of oxygen, requires the presence of a carbonaceous precursor and energetic processes in a N-dominated environment Ong et al 1996;Hammer et al 2000;Rodil et al 2001;Quirico et al 2008;Gerakines et al 2004;Moore et al 2003;Hudson et al 2001). Such conditions are gathered at the surface of some objects, which are orbiting at large heliocentric distances, beyond the trans-Neptunian region, with N 2 -rich icy surfaces (Schaller & Brown 2007;Levi & Podolak 2011). The energetic process can indeed be provided by irradiation with cosmic rays and/or visible-ultraviolet (VUV) photons (Cooper et al 2003).…”