List of missions to comets & year of launch - Wiki
ICE - NASA / ESA 1978
Vega 1 & 2 - Soviet Union 1984
Sakigake & Suisei - Japan 1985
Giotto - ESA 1985
(Stardust, NASA, 1999 & Deep Impact, NASA, 2005)
19P / Borrelly (Deep Space 1, NASA, 1998)
21P / Giacobini–Zinner (ICE, NASA / ESA, 1978)
26P / Grigg–Skjellerup (Giotto, ESA, 1985)
67P / Chury (Rosetta, ESA, 2004)
103P / Hartley (Deep Impact, NASA, 2005)
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Title - Peculiar Comets Ejected Early in Solar System Formation
By - Anderson et al, 2022
Summary - The scarcity of CO- and N2- rich comets such as C/2016R2 PanSTARRS could be explained by early solar system dynamics near the CO and N2 icelines.
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By - E. Lellouch et al, Jan 2022
Summary - The brightness of Comet Bernardinelli-Bernstein (Hr ~ 8.0) indicates an exceptionally large object, predicted to be 137 km wide, and is hence claimed to be the largest known comet in the Solar System (almost twice as large as the 60 km wide comet C/1995 O1 Hale-Bopp). Its activity is driven by hypervolatiles. It was discovered inbound as far as ~29 au from the Sun, with prediscovery images up to ~34 au, It showed cometary activity already at almost 24 au. The comet is heading towards a 11 au perihelion in 2031.
My view : The centaur object 95P / Chiron should be considered as the biggest comet. It is 200 km wide & shows cometary activity. Not considering it as the biggest comet is illogical.
My Twitter thread on this paper
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Title - A rapid decrease in the rotation rate of comet 41P
By - Dennis Bodewits et al, 2018
Summary -
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Title - Comet C/2009 P1 & comet 41P
By - Dennis Bodewits et al, Jan 2023
Summary - Comet 41P's rotation period decreased from 10 hours to 48 hours in just 2 months !
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Title - Photodissociation of dicarbon: How nature breaks an unusual multiple bond
By - Jasmin Borsovszky et al, 2021
Summary - The dicarbon molecule (C2) is responsible for the green color of the coma of a comet, but it is not found in the tail. It has long been held to photodissociate in sunlight with a lifetime precluding observation in the tail, but the mechanism was not known. Here we directly observe photodissociation of C2.
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Title - Comet 108P/Ciffreo: The Blob
By - Yoonyoung Kim, David Jewitt et al, Feb 2023
Summary - Short-period comet 108P/Ciffreo is known for its peculiar double morphology (similar to comet 17P / Holmes and centaur 174P/Echeclus, entry 13 in this page), in which the nucleus is accompanied by a co-moving, detached, diffuse 'blob'. The separation and the longevity of the blob across several orbits together rule out the possibility of a single, slow-moving secondary object near the primary nucleus. Extracts. My Twitter thread on it.
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By - Man-To Hui, Quan-Zhi Ye, 2020
Summary - During Jan-April, 2020, Comet C/2019 Y4 (ATLAS) brightened up at pre-perihelion & faded. We conclude that the comet has disintegrated since mid-March 2020. By no means was the split new to the comet, as we quantified that the comet had undergone another split event around last perihelion ∼5 kyr ago, during which its sibling C/1844 Y1 (Great Comet) was produced. We constrained that the nucleus of C/2019 Y4 before disintegration was ≳60 m in radius, and has been protractedly ejecting dust grains of 10-40 μm (assuming dust bulk density 0.5 g cm−3) with ejection speed 30 m/s in early March 2020 and increased to 80 m/s towards the end of the month for grains of 10 μm.
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Title - Water ice and dust in the innermost coma of comet 103P/Hartley 2
By - Silvia Protopapa et al, 2014
Summary - .
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Title - Split Comets
By - Boehnhardt, 2004
Summary - More than 40 split comets have been observed over the past 150 years. Two of the split comets have disappeared completely; another one was destroyed during its impact on Jupiter. The analysis of the post-splitting dynamics of fragments suggests that nucleus splitting can occur at large heliocentric distances (certainly beyond 50 AU) for long period and new comets and all along the orbit for short-period comets. Various models for split comets have been proposed, but only in one peculiar case, the break-up of Comet D/1993 F2 (Shoemaker-Levy 9) around Jupiter, has a splitting mechanism been fully understood: The nucleus of D/1993 F2 was disrupted by tidal forces. The fragments of split comets seem to be sub-kilometer in size. It is, however, not clear whether they are cometesimals that formed during the early formation history of the planetary system or are pieces from a heavily processed surface crust of the parent body. The 2 basic types of comet splitting (few fragments and many fragments) may require different model interpretations. Disappearing comets may represent rare cases of complete nucleus dissolution as suggested by the prototype case, Comet C/1999 S4 (LINEAR). At least one large family of split comets exists — the Kreutz group— but other smaller clusters of comets with common parent bodies are very likely. Comet splitting seems to be an efficient process of mass loss of the nucleus and thus can play an important role in the evolution of comets toward their terminal state. The secondary nuclei behave as comets of their own (with activity, coma, and tail) exhibiting a wide range of lifetimes. However, at present it is not known whether the fragments’ terminal state is “completely dissolved” or “exhausted and inactive.” This paper discusses fragmentation mechanisms & includes a list of split comets, likely split pairs, and families of split comets.
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Title - Coma morphology and dust emission pattern of comet C/2020 F3 (NEOWISE)
By - F Manzini et al, 2021
Summary - The comet is strongly emitting gas and dust, at high ejection speed, most likely from two different active sources located in almost symmetrical positions at mid-latitudes on the nucleus. A possible third source, located in near-polar position was also hypothesised. The comet has a prograde rotation & its spin axis was directed towards the Earth during the whole observation period, and spirals and shell-shaped structures, deriving from the active sources, were visible in the inner coma. Its rotation period is 7.8 hours. The coma is probably composed of a wide range of dust sizes (between 0.80 and 800 µm). The dust was more concentrated in the subsolar sector in the first two shells, while the gas component was predominant from the third shell to the edge of the coma.
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Title - Icy Grains from the Nucleus of Comet C/2013 US10 (Catalina)
By - Silvia Protopapa et al, 2018
Summary - .
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Title - Comet C/2011 J2 (LINEAR) nucleus splitting: Dynamical and structural analysis
By - F Manzini et al, 2016
Summary - .
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Title - Motion of the Activity Source Associated with Active Centaur 174P/Echeclus (60558)
By - Paul Weissman et al, 2006
Summary - Centaur (60558) Echeclus was discovered to be active by Choi et al. (IAUC 8656, 2006) on December 30, 2005 and subsequently renamed comet 174P/Echeclus. Observations during the next five months showed that the apparent source of activity moved away from the primary body to a maximum distance of 65,000 km at the comet, in late Feb, 2006. The activity source then moved back towards and past the primary to only 2.7 arc-seconds in early May, 2006. Although the apparent motion suggested an orbiting secondary, the speed with which the secondary moved over the distances involved is inconsistent with reasonable estimates of the mass of the primary, by a factor of 200 or more. We thus believe that the secondary object is more likely moving on a hyperbolic orbit relative to the primary. Plausible explanations for the existence of the active secondary are: (1) a large fragment ejected from the primary in a disruption event; (2) an impact on the primary by another small solar system body; or (3) an escaped satellite of the primary. The lack of comparable activity from the primary body at the site of the disruption or impact argues against explanations (1) and (2). Although the existence of a Centaur with a satellite is highly plausible, it is doubtful that nongravitatonal forces resulting from outgassing at that heliocentric distance would be sufficient to explain the escape.
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Title - Discovery of Cometary Activity for Centaur 174P/Echeclus (60558)
By - Young-Jun Choi & Paul Weissman, 2006
Summary - We report the first detection of cometary activity in Centaur 174P/Echeclus. Centaur (60558) 2000 EC98, its previous designation, was originally classified as an asteroidal body with no visible sign of coma or non-rotational photometric variations since its discovery in 2000. However, a massive cometary outburst was detected in Dec 2005. The object was subsequently assigned the designation 174P/Echeclus. Total magnitude of 174P was R = 15.0 at the time of the discovery of activity, while the magnitude of the bare nucleus was expected to be only R 20.0. The coma showed asymmetric structure with 2 major inner arcs and a well-shaped outer boundary, and extended 20 arc-seconds from the nucleus condensation, equivalent to a projected distance of 190,000 km at the comet's distance of 13.07 AU. The coma expanded with a projected velocity of 500-800 m/sec, which implies that even the outermost material in the coma left the nucleus only 3 to 4 days before the detection of the outburst. Color profiles as a function of radial distance from the nucleus showed a color gradient in the coma, and dust production rates of 300 - 600 kg/sec were measured in the BVRI filter passbands. We also found evidence of cometary activity in pre-discovery images of 174P/Echeclus from the Spacewatch archive.
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Title - Two Years After Cometary Activity of Centaur (60558) 174P/Echeclus
By - Young-Jun Choi & Paul Weissman, 2008
Summary - The dust production rate was 200-400 kg/sec in both the visual and IR. Total infrared fluxes for the coma were about 6 times stronger than for the bare nucleus before the onset of activity. Observations during the 7 months after the initial detection of activity showed that the apparent source of activity moved away from the primary body to a maximum distance of 65,000 km in late Feb, 2006, then moved back towards and past the Centaur in late July, 2006. The first question was what the nature of the comet was, whether it was a fragment ejected from the Centaur at the onset of activity, or was it a companion of the Centaur. It appears the comet has an orbit that is very similar to that of the Centaur but independent, and it may not have been ejected from the Centaur at this apparition. We cannot rule out that the comet was a fragment separated from the Centaur as a result of a major outburst or as a result of a collision with a small comet or asteroid. But if either of these is the case, then what is the reason that the Centaur is not active while the comet was active in 2005-2006 ? A possible explanation for the activity of the comet is either that the comet had an outburst like Chiron or that the comet collided with other fragments of the Centaur that might exist in the same orbit. Thermal calculations for objects having similar orbits with 174P support the existence of the small comet indirectly, if the outburst was triggered by the water ice amorphous-to-crystal process in its interior. In that case the outburst is likely to last longer than 6 months, for objects larger than 10 km diameter.
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By - Federico Manzini, 2007
Summary - .
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Title - Evolution of mobile phases in cometary interiors
By - Christopher Fellows, Trevor Brown, Andrew Cooper, Marco Parigi, 2020
Summary - We conclude that the likely temperatures, pressures, and compositions beneath the outer crust of typical cometary nuclei are such that fluidised phases can exist at significant depths and that these reservoirs give a coherent explanation for the high-intensity outbursts observed from cometary nuclei at large distances from perihelion. An interior atmosphere at a significant pressure is a prerequisite for high-volume eruptions from comets, persistence of cometary activity at a significant distance from perihelion, and for existence of liquid phases at any point in a cometary lifetime. We have estimated the likely composition of an atmosphere derived from initial sublimation of outer surfaces of a cometary nucleus and discussed the likely consequences of the existence of such an atmosphere. The principal difference between our estimates and previous work is that we find that pristine comets should fill with gas in the years or centuries after first perihelion due to the low sublimation temperatures of volatile components such as CO, leaving no truly pristine material in the interior. We note that the complexity and processed nature of the observed surface of comet 67P, and the high-volume eruptions at far from perihelion distances observed (Halley’s Comet at a distance of 14 AU), are explicable in terms of these consequences, while they are not compatible with a process of ablation of a pristine frozen core. It is time to retire the conception of comets as pristine remnants of the infant solar system and consider them as bodies which have experienced a complex history before coming into our view.
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Title - 13 comet papers from LPSC 2023
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Title - C/2010 U3 (Boattini): A Bizarre Comet Active at Record Heliocentric Distance
By - Man-To Hui et al, 2019
Summary - .
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Title - Contemporaneous Multiwavelength and Precovery Observations of the Active Centaur P/2019 LD2 (ATLAS)
By - Theodore Kareta et al, 2021
Summary - .
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Title - Physical and Surface Properties of Comet Nuclei from Remote Observations
By - Matthew Knight et al, 2023
Summary - Collective knowledge of physical and surface properties of numerous comets are summarized in this paper, with a focus on those that are obtained from remote observations. One of the surprising findings was that rotation period changes seem to be nearly independent of the active fraction of the nucleus. Samarasinha and Mueller (2013), based on 6 (4+2) periodic comets, pointed out that the rotation period changes seem to be independent of the active fraction of a nucleus, where active fraction is the fractional surface area of a solid water ice nucleus needed to reproduce the observed water production of the comet. They suggest that highly active comets undergo more cancellation of torques. The most direct conclusion from this spin evolution analysis is comets that have large active fractions show similar rotational evolution to comets with small active fractions. The exceptions appear to be comets with very low active fractions (0.1%), where the sublimative torques are apparently too weak to cause any spin evolution.
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Title - Nuclear and Orbital Characterization of the Transition Object (4015) 107P/Wilson-Harrington
By - Theodore Kareta & Vishnu Reddy, 2023
Summary - Comet 107P/Wilson-Harrington, cross-listed as asteroid 4015, is one of the original transition objects whose properties do not neatly fit into a cometary or asteroidal origin. The object's spectrum is well matched by laboratory spectra of carbonaceous chondrite meteorites like the CM Murchison or the CI Ivuna. The object's phase curve is compatible with either an asteroidal or cometary origin, and its recent orbital history has no periods with high enough temperatures to have altered its surface. While it is possible that some unknown process has acted to change the surface from an originally cometary one, we instead prefer a fundamentally asteroidal origin for Wilson-Harrington, which can explain its surface and orbital properties. However, this would require a way to maintain significant (hyper-)volatile supplies on the near-Earth objects beyond what is currently expected. Wilson-Harrington's similar meteorite affinity and possible orbital link to Ryugu and Bennu suggest that the returned samples from the Hayabusa-2 and OSIRIS-REx missions might hold the key to understanding this object.
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