Proton Irradiation of Centaur, Kuiper Belt, and Oort Cloud Objects at Plasma to Cosmic Ray Energy
TL;DR: In this paper, the authors present model flux spectra derived from spacecraft data and models for eV to GeV protons at 40 AU, a termination shock position at 85 AU, and galactic cosmic ray ions from the Local Interstellar Medium (LISM).
Abstract: Times for accumulation of chemically significant dosages on icy surfaces of Centaur, Kuiper Belt, and Oort Cloud objects from plasma and energetic ions depend on irradiation position within or outside the heliosphere. Principal irradiation components include solar wind plasma ions, pickup ions from solar UV ionization of interstellar neutral gas, energetic ions accelerated by solar and interplanetary shocks, including the putative solar wind termination shock, and galactic cosmic ray ions from the Local Interstellar Medium (LISM). We present model flux spectra derived from spacecraft data and models for eV to GeV protons at 40 AU, a termination shock position at 85 AU, and in the LISM. Times in years to accumulate dosages ~100 eV per molecule are computed from the spectra as functions of sensible surface depth less than one centimeter at unit density. The collisional resurfacing model of Luu and Jewitt is reconsidered in the context of depth-dependent dosage rates from plasma, suprathermal, and higher energy protons, and global exposure, by micrometeoroid dust grain impacts, of moderately irradiated red material below a thin crust of heavily irradiated neutral material. This material should be more visible on dynamically ‘cold’ objects in the ~40 AU region.
Citations
More filters
Lowell Observatory1, Massachusetts Institute of Technology2, Jet Propulsion Laboratory3, Southwest Research Institute4, Ames Research Center5, Search for extraterrestrial intelligence6, Goddard Space Flight Center7, University of Grenoble8, University of Maryland, College Park9, University of Virginia10, Johns Hopkins University Applied Physics Laboratory11, Stanford University12, Lunar and Planetary Institute13, Space Telescope Science Institute14, Planetary Science Institute15
TL;DR: The New Horizons team presents the complex surface features and geology of Pluto and its large moon Charon, including evidence of tectonics, glacial flow, and possible cryovolcanoes, as well as their analysis of the encounter data downloaded so far.
Abstract: The New Horizons spacecraft mapped colors and infrared spectra across the encounter hemispheres of Pluto and Charon. The volatile methane, carbon monoxide, and nitrogen ices that dominate Pluto's surface have complicated spatial distributions resulting from sublimation, condensation, and glacial flow acting over seasonal and geological time scales. Pluto's water ice "bedrock" was also mapped, with isolated outcrops occurring in a variety of settings. Pluto's surface exhibits complex regional color diversity associated with its distinct provinces. Charon's color pattern is simpler, dominated by neutral low latitudes and a reddish northern polar region. Charon's near-infrared spectra reveal highly localized areas with strong ammonia absorption tied to small craters with relatively fresh-appearing impact ejecta.
270 citations
TL;DR: It is concluded that Quaoar has been recently resurfaced, either by impact exposure of previously buried (shielded) ices or by cryovolcanic outgassing, or by a combination of these processes.
Abstract: The Kuiper belt is a disk-like structure consisting of solid bodies orbiting the Sun beyond Neptune1. It is the source of the short-period comets and the likely repository of the Solar System's most primitive materials2. Surface temperatures in the belt are low (∼ 50 K), suggesting that ices trapped at formation should have been preserved over the age of the Solar System. Unfortunately, most Kuiper belt objects are too faint for meaningful compositional study, even with the largest available telescopes. Water ice has been reported in a handful of objects3,4,5, but most appear spectrally featureless5,6. Here we report near-infrared observations of the large Kuiper belt object (50000) Quaoar, which reveal the presence of crystalline water ice and ammonia hydrate. Crystallinity indicates that the ice has been heated to at least 110 K. Both ammonia hydrate and crystalline water ice should be destroyed by energetic particle irradiation on a timescale of about 107 yr. We conclude that Quaoar has been recently resurfaced, either by impact exposure of previously buried (shielded) ices or by cryovolcanic outgassing, or by a combination of these processes.
257 citations
161 citations
TL;DR: In this article, the authors reexamine the scattered disk as a source of the short-period Jupiter family comets and make a rigorous estimate of the discrepancy between the best estimates from observational surveys and theoretical models of the dynamical evolution of Kuiper Belt objects into JFCs.
Abstract: The short-period Jupiter family comets (JFCs) are thought to originate in the Kuiper Belt; specifically, a dynamical subclass of the Kuiper Belt known as the "scattered disk" is argued to be the dominant source of JFCs. However, the best estimates from observational surveys indicate that this source may fall short by more than 2 orders of magnitude of the estimates obtained from theoretical models of the dynamical evolution of Kuiper Belt objects into JFCs. We reexamine the scattered disk as a source of the JFCs and make a rigorous estimate of the discrepancy. We find that the uncertainties in the dynamical models combined with a change in the size distribution function of the scattered disk at faint magnitudes (small sizes) beyond the current observational limit offer a possible but problematic resolution to the discrepancy. We discuss several other possibilities: that the present population of JFCs is a large fluctuation above their long-term average, that larger scattered disk objects tidally break up into multiple fragments during close planetary encounters as their orbits evolve from the trans-Neptune zone to near Jupiter, or that there are alternative source populations that contribute significantly to the JFCs. Well-characterized observational investigations of the Centaurs, objects that are transitioning between the trans-Neptune Kuiper Belt region and the inner solar system, can test the predictions of the non-steady state and the tidal breakup hypotheses. The classical and resonant classes of the Kuiper Belt are worth reconsideration as significant additional or alternate sources of the JFCs.
157 citations
Cites background from "Proton Irradiation of Centaur, Kuip..."
...Cooper et al. (2003) discuss the effect of these different radiation environments combined with several resurfacing processes on the colors of the various dynamical classes of KBOs, finding some evidence that the classical belt is best situated for producing red objects, while other classes would…...
[...]
TL;DR: In this article, the authors present observations of the interstellar interloper 1I/2017 U1 ('Oumuamua') taken during its 2017 October flyby of Earth.
Abstract: We present observations of the interstellar interloper 1I/2017 U1 ('Oumuamua) taken during its 2017 October flyby of Earth. The optical colors B – V = 0.70 ± 0.06, V – R = 0.45 ± 0.05, overlap those of the D-type Jovian Trojan asteroids and are incompatible with the ultrared objects that are abundant in the Kuiper Belt. With a mean absolute magnitude H V = 22.95 and assuming a geometric albedo p V = 0.1, we find an average radius of 55 m. No coma is apparent; we deduce a limit to the dust mass production rate of only ~2 × 10−4 kg s−1, ruling out the existence of exposed ice covering more than a few m2 of the surface. Volatiles in this body, if they exist, must lie beneath an involatile surface mantle 0.5 m thick, perhaps a product of prolonged cosmic-ray processing in the interstellar medium. The light curve range is unusually large at ~2.0 ± 0.2 mag. Interpreted as a rotational light curve the body has axis ratio :1 and semi-axes ~230 m × 35 m. A 6:1 axis ratio is extreme relative to most small solar system asteroids and suggests that albedo variations may additionally contribute to the variability. The light curve is consistent with a two-peaked period ~8.26 hr, but the period is non-unique as a result of aliasing in the data. Except for its unusually elongated shape, 1I/2017 U1 is a physically unremarkable, sub-kilometer, slightly red, rotating object from another planetary system. The steady-state population of similar, ~100 m scale interstellar objects inside the orbit of Neptune is ~104, each with a residence time of ~10 years.
153 citations
References
More filters
Book•
IBM1
TL;DR: A review of existing widely-cited tables of ion stopping and ranges can be found in this paper, where a brief exposition of what can be determined by modern calculations is given.
Abstract: The stopping and range of ions in matter is physically very complex, and there are few simple approximations which are accurate. However, if modern calculations are performed, the ion distributions can be calculated with good accuracy, typically better than 10%. This review will be in several sections:
a)
A brief exposition of what can be determined by modern calculations.
b)
A review of existing widely-cited tables of ion stopping and ranges.
c)
A review of the calculation of accurate ion stopping powers.
10,060 citations
[...]
01 Jan 1961
TL;DR: The major Reformation of the 16th century is represented in the Netherlands most clearly by Cassander, Coornhert and Lipsius as mentioned in this paper, who follow one another chronologically in this order and they show in that order an increasing subjection to the influence of the Classics and a reduced need of supernatural salvation in the christian sense.
Abstract: What I have called the major Reformation of the 16th century is represented in the Netherlands most clearly by Cassander, Coornhert and Lipsius. They follow one another chronologically in this order and they show in that order an increasing subjection to the influence of the Classics and a reduced need of supernatural salvation in the christian sense. The first of these men is a Christian carrying out humanistic studies, while the third is a humanistic philosopher who is a faithful Christian as well.
1,812 citations
TL;DR: The Cosmic Ray on Micro-Electronics (CREME) as mentioned in this paper is a suite of programs for creating numerical models of the ionizing-radiation environment in near-Earth orbits and for evaluating radiation effects in spacecraft.
Abstract: CREME96 is an update of the Cosmic Ray on Micro-Electronics code, a widely-used suite of programs for creating numerical models of the ionizing-radiation environment in near-Earth orbits and for evaluating radiation effects in spacecraft. CREME96, which is now available over the World-Wide Web (WWW) at http://crsp3.nrl.navy.mil/creme96/, has many significant features, including: (1) improved models of the galactic cosmic ray, anomalous cosmic ray, and solar energetic particle ("flare") components of the near-Earth environment; (2) improved geomagnetic transmission calculations; (3) improved nuclear transport routines; (4) improved single-event upset (SEU) calculation techniques, for both proton-induced and direct-ionization-induced SEUs; and (5) an easy-to-use graphical interface, with extensive on-line tutorial information. In this paper we document some of these improvements.
605 citations
"Proton Irradiation of Centaur, Kuip..." refers background in this paper
...tra in the LISM are defined here from work of Webber and Potgieter (1989) for power-law flux spectra (vs....
[...]