Main-Belt Comets as Tracers of Ice in the Inner Solar System

Haghighipour

2016

Icarus

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We present the results of "snapshot" numerical integrations of test particles representing comet-like and asteroid-like objects in the inner solar system aimed at investigating the short-term dynamical evolution of objects close to the dynamical boundary between asteroids and comets as defined by the Tisserand parameter with respect to Jupiter, T J (i.e., T J = 3). As expected, we find that T J for individual test particles is not always a reliable indicator of initial orbit types. Furthermore, we find that a few percent of test particles with comet-like starting elements (i.e., similar to those of Jupiter-family comets) reach main-belt-like orbits (at least temporarily) during our 2 Myr integrations, even without the inclusion of nongravitational forces, apparently via a combination of gravitational interactions with the terrestrial planets and temporary trapping by mean-motion resonances with Jupiter. We estimate that the fraction of real Jupiter-family comets occasionally reaching main-belt-like orbits on Myr timescales could be on the order of ∼ 0.1-1%, although the fraction that remain on such orbits for appreciable lengths of time is certainly far lower. For this reason, the number of JFC-like interlopers in the main-belt population at any given time is likely to be small, but still non-zero, a finding with significant implications for efforts to use apparently icy yet dynamically asteroidal main-belt comets as tracers of the primordial distribution of volatile material in the inner solar system. The test particles with comet-like starting orbital elements that transition onto main-belt-like orbits in our integrations appear to be largely prevented from reaching low eccentricity, low inclination orbits, suggesting that the real-world population of main-belt objects with both low eccentricities and inclinations may be largely free of this potential occasional Jupiter-family comet contamination. We therefore find that low-eccentricity, low-inclination main-belt comets may provide a more reliable means for tracing the primordial ice content of the main asteroid belt than the main-belt comet population as a whole.

Section: Main-belt Cometsmentioning

confidence: 99%

Section: Mbc Origins and Reliability As Compositional Tracersmentioning

confidence: 99%

Potential Jupiter-Family comet contamination of the main asteroid belt

Haghighipour

2016

Icarus

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“…First recognized as a new class of cometary objects in 2006 [44], MBCs have attracted interest because the unexpected present-day ice (given their location in the warm inner solar system) implied by their apparently sublimation-driven activity mean that they could potentially be used as compositional probes of inner solar system ice and also as a means of testing hypotheses that icy objects from the main-belt region of the solar system could have played a significant role in the primordial delivery of water to the terrestrial planets [52,95,96,101]. While both meteoritic and spectroscopic evidence of past water in main-belt asteroids has long been available in the form of detections of hydrated minerals in both meteorites linked to asteroids in the main belt and remote spectroscopy of the asteroids themselves [13,39,71,102], the activity observed for MBCs points to the existence of currently present water ice in the asteroid belt that could represent some of the best preserved material from this part of the solar system available for study today.…”

Section: (Ii) Main-belt Cometsmentioning

confidence: 99%

Asteroid–comet continuum objects in the solar system

Phil. Trans. R. Soc. A.

2017

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In this review presented at the Royal Society meeting, ‘Cometary science after Rosetta’, I present an overview of studies of small solar system objects that exhibit properties of both asteroids and comets (with a focus on so-called active asteroids). Sometimes referred to as ‘transition objects’, these bodies are perhaps more appropriately described as ‘continuum objects’, to reflect the notion that rather than necessarily representing actual transitional evolutionary states between asteroids and comets, they simply belong to the general population of small solar system bodies that happen to exhibit a continuous range of observational, physical and dynamical properties. Continuum objects are intriguing because they possess many of the properties that make classical comets interesting to study (e.g. relatively primitive compositions, ejection of surface and subsurface material into space where it can be more easily studied, and orbital properties that allow us to sample material from distant parts of the solar system that would otherwise be inaccessible), while allowing us to study regions of the solar system that are not sampled by classical comets. This article is part of the themed issue ‘Cometary science after Rosetta’.

“…Morbidelli et al 2000Morbidelli et al , 2012Mottl et al 2007;Owen 2008), and possibly gain insights into the conditions that allowed life to arise on Earth and that might be needed for life to arise in other extrasolar planetary systems (cf. Hsieh 2014).…”

Section: Introductionmentioning

confidence: 99%

Main-belt comets: sublimation-driven activity in the asteroid belt

2015

Proc. IAU

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Abstract. Our knowledge of main-belt comets (MBCs), which exhibit comet-like activity likely due to the sublimation of volatile ices, yet orbit in the main asteroid belt, has increased greatly since the discovery of the first known MBC, 133P/Elst-Pizarro, in 1996, and their recognition as a new class of solar system objects after the discovery of two more MBCs in 2005. I review work that has been done over the last 10 years to improve our understanding of these enigmatic objects, including the development of systematic discovery methods and diagnostics for distinguishing MBCs from disrupted asteroids (which exhibit comet-like activity due to physical disruptions such as impacts or rotational destabilization). I also discuss efforts to understand the dynamical and thermal properties of these objects.