Planetary and Space Science 118 (2015) 1–7

Contents lists available at ScienceDirect

Planetary and Space Science

journal homepage: www.elsevier.com/locate/pss

Editorial , , Meteors, and their Interrelations, Part I: Editorial review

1. Introduction than 40 countries at the conference (Fig. 1). The ACM 2014 Book of Abstracts included over 600 abstracts (Muinonen et al., 2014). It is widely agreed that the small Solar System bodies are a key Plenary, Parallel, and Poster Sessions were organized around to understanding the formation and evolution of the Solar System, numerous topical themes. The Plenary Sessions focused on the carrying signals from pre-solar times. Unveiling the evolution of Rosetta mission, ISON, and the Chelyabinsk meteor on the Solar System helps research on the evolution of extrasolar Monday, with formation, main-belt dynamical evolution, planetary systems. Societally, small bodies will be important the Dawn mission, and Chariklo's rings featured on Tuesday. future resources of minerals. The near-Earth population of small Thursday's Plenary Session featured the Gaia mission, both overall bodies continues to pose an impact hazard, whether it be small and as a Solar System observatory, as well as state-of-the-art pieces of falling meteorites or larger asteroids or cometary nuclei meteor observing and the New Horizons mission to Pluto, whereas capable of causing global environmental effects. the Friday Plenary focused on the past Hayabusa, future Haya- In Section 2, we begin by a review of the Asteroids, Comets, busa2, past Chang'e-2, and future OSIRIS-REx asteroid missions. Meteors 2014 conference in Helsinki. In Section 3, the advances The Parallel and Poster Sessions included the following themes. documented in the peer-reviewed papers included in the present Sessions assessing all populations of small bodies included Planetary and Space Science Special Issue topically entitled Aster- oids, Comets, Meteors, and their Interrelations, Part I are reviewed. Surveys of small bodies The editorial review is completed by conclusions and future pro- Impact hazard spects in Section 4. Missions Absorption, Scattering, and Emission Extrasolar connection. 2. Asteroids, Comets, Meteors 2014 Comets were featured in the sessions entitled 2.1. Overall review Rosetta and Comet 67/P Churyumov–Gerasimenko The Asteroids, Comets, Meteors conference series constitutes Comet ISON the leading international series in the field of small Solar System Specific Comets bodies. The first three conferences took place in Uppsala, Sweden Comet surfaces and interiors in 1983, 1985, and 1989, followed by the conferences in Flagstaff, Comet formation and evolution. Arizona, USA in 1991, Belgirate, Italy in 1993, Paris, France in 1996, Ithaca, New York, USA in 1999, Berlin, Germany in 2002, Rio de For , meteors, and meteorites, there were sessions Janeiro, Brazil in 2005, Baltimore, Maryland, USA in 2008, Niigata, on Japan in 2012, and Helsinki, Finland in 2014. The ACM 2014 conference was organized by the Department of Chelyabinsk meteor, meteorites, and active asteroids Physics, University of Helsinki at the Marina Congress Centre in Meteoroids and meteorites Katajanokka, Helsinki (see Appendix A for the members of the Meteor surveys Scientific and Local Organizing Committees). The conference was Meteoroids, dust, and exospheres. opened at the Helsinki Observatory, spiced with the sporadic rain of hydrometeors and cold weather. The conference itself was Asteroid research was scrutinized in the sessions entitled organized as follows: a plenary session gathered the attendees together each morning, except for Wednesday where the after- Asteroid spin, size, and shape noon excursions and evening dinner resulted in an exceptional Ceres and Lutetia morning program of parallel sessions. The morning plenaries were Vesta followed by a coffee break and a poster session that ended in the Dynamics and populations lunch break. The afternoons were filled with parallel sessions Asteroid surfaces except for Friday, where there was a plenary session with invited Asteroid collisions and families reviews on meteors, comets, and asteroids, followed by the closing Asteroid interiors of the conference. There were almost 500 attendees from more Specific asteroids http://dx.doi.org/10.1016/j.pss.2015.11.001 0032-0633/& 2015 Published by Elsevier Ltd. 2 Editorial / Planetary and Space Science 118 (2015) 1–7

Solar system science with Gaia ample informal time for talking with colleagues. Is this Satellites and binary systems. arrangement satisfactory to repeat at the next ACM? 6. If your answer to the previous question was 'NO', when would Finally, additional sessions, focusing on specific objects and you prefer to have the poster session organized? populations included Compared to ACM 2014, most of the attendees who responded Pluto and transneptunian objects to the questionnaire would like to have fewer parallel sessions, not Jupiter Trojans. have longer talks, days of similar length, a maximum of one con- tributed talk per participant, and a similar poster session (Fig. 2). Among the abovementioned sessions, there were two special The minority of attendees who would like to move the poster workshops running at the conference: first, Absorption, Scattering, session would typically want to see it arranged during the and Emission; and, second, Solar System Science with Gaia, afternoon. showing the first results on small bodies from the Gaia mission. The attendees that provided written feedback suggested that future meetings should have, for example, fewer parallel sessions, poster sessions lasting the entire week, and a clear view of the 2.2. Guidelines from the community to future organizers of ACM screen also from the back row in all rooms. meetings In general the feedback shows that the attendees in general were very pleased with the arrangements of ACM 2014 but there is We asked the attendees to fill a short questionnaire after the still room for improvement at future meetings. meeting to get a quantitative understanding of the community's opinion about the arrangements for ACM 2014. The aim was to give the organizing committees of future ACM meetings an idea of how the community would like to see the practical arrangements 3. Regular papers of special issue of the ACM conference series evolve. We got 78 unique responses which is more than 15% of all attendees. 3.1. Interrelations Most of the questions focused on the number and duration of contributed talks, because there were about 450 contributed 8- Interrelations between the different small-body populations is one of the main themes among the articles submitted for this min talks scheduled for ACM 2014 and 4 parallel sessions were special issue. We expect this trend to continue and become even required to accommodate these within the available days. The more prominent in the future, not least due to the ability to esti- sessions ran from 8:30 am to about 6:00 pm, except for Wed- mate physical properties for ever larger samples of objects. nesday when the scientific program ended at noon due to the State-of-the-art meteor observations and the link between afternoon excursions. We asked the attendees the following 5–6 asteroids and meteors is discussed by Campbell-Brown (2015) multiple-choice questions and also offered the possibility to pro- who describes the Canadian Automated Meteor Observatory and vide written feedback. presents the results from an analysis of more than 7000 two- station meteors. The analysis reveals a significant population of 1. Would you prefer to reduce the likelihood that you will be slow meteors with low begin heights and asteroidal orbits. The scheduled for a talk during future ACM meetings in exchange for fewer parallel sessions? radiants of these slow meteors are not associated with sporadic 2. Would you prefer to reduce the likelihood that you will be sources and their lightcurves cannot be reproduced with classical scheduled for a talk during future ACM meetings in exchange ablation theory for non-fragmenting objects. for longer talks? The connection between near-Earth comets and outer main- 3. A meeting can have more time for talks each if the start belt asteroids is discussed by Fernandez and Sosa (2015). They time is earlier and the end is later. Given that shorter days analyze the dynamical evolution of a sample of Jupiter-family would reduce the likelihood that you will be scheduled for a comets (JFCs) among near-Earth objects, selected based on the talk and that longer days would do the opposite, how long Tisserand parameter and . one third of the sample should the days be compared to ACM 2014? have short dynamical lifetimes in agreement with the expected 4. At ACM 2014, each participant was allowed at most two con- short physical lifetime for icy objects, whereas one third has long tributed talks. What is the maximum number of contributed dynamical lifetimes with orbits resembling near-Earth asteroids talks that should be allowed for a single participant? originating in the outer main . Fernandez and Sosa 5. The poster sessions were arranged between 10:30 am and 11:30 propose that the cometary and asteroidal JFCs should be compo- am bracketed by coffee and lunch. The aim was to allow for sitionally different to explain the longer lifetimes of the latter.

Fig. 1. : Participants of the Asteroids, Comets, Meteors 2014 conference in Helsinki, Finland. Editorial / Planetary and Space Science 118 (2015) 1–7 3

Question 1 Question 2 Question 3 60 50 30 35 50 40 30 20 25 15 20 010 0510 010203040 Neutral No Yes Neutral No Yes Longer Shorter Similar

Question 4 Question 5 Question 6 40 30 30 40 50 20 10 20 0 010 0246810 123 Neutral No Yes Afternoon Evening Morning

Fig. 2. : The distribution of responses to the questionnaire. See text for list of questions.

Rudawska and Vaubaillon (2015), Hajdukova et al. (2015), and The selection of the stream meteors from the European viDeo Tomko (2015) search for associations between meteor showers MeteOr Network Database (EDMOND) is detailed by Rudawska and asteroids or comets. Rudawska and Vaubaillon (2015) analyze et al. (2015) and Kornos et al. (2015). The latter study, Kornos et al. the connections between known meteor showers and the recently (2015), focuses on observational data of the Lyrid meteor shower activated asteroid (3552) Don Quixote, now considered a JFC. They and on the gravitational orbital evolution of its parent long-period model the dynamical evolution of hypothetical meteor streams comet C/1861 G1 (Thatcher) accompanied by theoretical modeling that originated on (3552) Don Quixote during perihelion passages of particles ejected in five perihelion passages of the comet in the in the past 5000 years and find that the meteor streams would past. Rudawska et al. (2015) suggest a method to identify statis- produce meteor showers on the Earth. Rudawska and Vaubaillon tically significant samples, representing meteor showers, in propose two showers that may be associated to (3552) Don meteor orbit databases. The study includes a detailed list of Quixote. Hajdukova et al. (2015) takes the opposite approach and meteor showers identified by the proposed method using the studies the dynamical evolution of synthetic meteor streams EDMOND database and compares the results with previously similar to April Rho Cygnids. With the data available they can published associations obtained by different methods. neither refute nor confirm the proposed connection between April Andronikov et al. (2015) use electron microprobe and laser- Rho Cygnids and comet C/1917 F1 (Mellish). Tomko (2015) focuses ablation inductively-coupled-plasma mass spectrometry (LA-ICP- fi on a stream model developed for the Halley-type comet MS) techniques to study the sul des and metals of two fragments 12P/Pons-Brooks. Only about 12% of the test particles in the syn- of the Chelyabinsk meteorite. The fragments represent chondritic thetic meteor stream approach the Earth's orbit within 0.05 au. impact breccia with shock veins, and vesicular impact melt with Despite a well-defined radiant, Tomko cannot find any associations shock darkened clasts. The different fragments and the analysis done suggest that the Chelyabinsk parent body has experienced at between known meteor showers and the theoretically modeled least two separate shock events. stream and, consequently, with comet 12P/Pons-Brooks. Radiative characteristics of the Chelyabinsk fireball, occurred on February 15, 2013, are analyzed based on the selected dash- 3.2. Meteors board video registration of the event by Yanagisawa (2015). The author obtains the lightcurve in the red, green, and blue color Events caused by a meteoroid's entry into the terrestrial atmo- bands. The results are discussed in the context of the earlier sphere take place regularly: meteoroids bombard the Earth at the meteor spectral studies conducted based on dedicated profes- rate of more than 100 tons a day. The initiated meteors determine sional measurements and/or based on theoretical constraints. the linkages between meteorites, meteor streams, and their parent Madiedo (2015) presents results of spectroscopic analysis of the bodies, and eventually allow the origin and the evolution of these kappa-Cygnid fireball observed by the SPanish Meteor Network parent comets and asteroids to be better understood. The meteor- (SPMN) on August 15, 2012. The study incorporates results on the related papers comprising the present special issue cover various atmospheric trajectory reconstruction, derived radiant and pre- topics, such as, multi-technique observations and subsequent data impact heliocentric orbit of the meteoroid, while emphasis is analysis, meteor shower identification, orbital behavior of the par- made on the evolution of the intensities of the main emission lines ent bodies, and evolution of meteoroid orbits under planetary in the afterglow spectra recorded by the SPMN for about 0.7 sec- perturbations and under non-gravitational effects. onds after the actual fireball. 4 Editorial / Planetary and Space Science 118 (2015) 1–7

Michell et al. (2015a, 2015b) report results obtained in the Along with the nominal peak of the shower, a new peak was also measurement campaign dedicated to meteor head echoes with the found in 2013. Southern Argentina Agile MEteor Radar (SAAMER) and simulta- neous optical detections. The multi-technique approach to meteor 3.3. Comets observations is of great scientific interest, as it minimizes the number of unknowns in the subsequent modeling and, in parti- The observations of comet ISON (C/2012 S1) are the topic of fi cular, sheds light on the values of ionization and luminous ef - three articles in this issue. Samarasinha et al. (2015) report the fi ciency coef cients which otherwise are poorly constrained. The results of the global observing campaign for the comet. The coma difference, as compared to the previous High Power and Large morphology was observed in 25 locations worldwide involving Aperture radar meteor observation campaigns, is the usage of the both professional and amateur observers. With this kind of dis- SAAMER, built in its original form for the detection of specular tributed campaign the authors were able to collect continuum and meteor trails and not for the weaker radar scattering signatures gas images of the near-nucleus region of the comet from different (Janches et al. 2014). The location of the radar in southern lati- longitudes. Faggi et al. (2015) report the results from ammonia tudes, where so far professional meteor observations are rare, emission study in the comets coma using the K-band Medicina brings the added scientific value to the obtained results. Out of 150 antenna in Bologna, Italy. They are able to constrain the NH3 total detections, 6 meteor events were identified where optically- production rate with an upper bound that is also consistent with detected meteors could also be clearly seen within the main results from the whole ISON campaign. Zubko et al. (2015) analyze radar beam. the first color and polarization images of comet ISON obtained by A semi-autonomous video observatory for meteor detections – the Hubble Space Telescope during two measurement campaigns the All-sky Meteor Orbit System (AMOS), its hardware and soft- in 2013. With the help of realistic modeling of the cometary dust ware development and permanent placement on several locations in terms of size and shape, Zubko et al. derive constraints on the in Slovakia – are described by Toth et al. (2015). The system material properties in the cometary coma. Their interpretation allowed the establishment of the Slovak Video Meteor Network points toward a heterogeneous composition of the cometary (SVMN), providing additional monitoring of meteor activity above coma: in the inner coma, small, highly-absorbing amorphous the Central Europe. The authors utilize data from several observing carbon or organics strongly altered by UV radiation can be favored, campaigns and present preliminary results on the exceptional and whereas, when moving outwards in the coma, the refractive rare meteor streams, such as epsilon Perseids originated from an indices of particles tend to agree with less-altered organics, tho- unidentified long-periodic comet on a retrograde orbit, possible lins, and silicates contaminated by amorphous carbon. asteroidal meteor stream of April alpha Comae Berenicids in the Markkanen et al. (2015) provide an inhomogeneous cometary orbit associated with the Pribram and Neuschwanstein meteorites, particle model based on a hierarchical Voronoi partitioning of the and the newly observed meteor stream Camelopardalids origi- particles. They compute the scattering properties of the inhomo- nated from the Jupiter family comet 209P (Linear). The idea to analyze meteors with derived hyperbolic orbits and geneous particles with their volume-integral-equation method draw conclusions as to the origin of such meteors is utilized by that has been proven to be an accurate method for particles fi Guliyev and Nabiyev (2015). The authors consider features of 238 showing high contrast in the refractive index. The rst results look hyperbolic meteors observed within the framework of the Japa- realistic and the model, as the natural next step ahead from the nese SonotaCo Network in the period of 2007–2009, and evaluate models by Zubko et al. above, has particularly bright future pro- astronomical aspects which could influence a part of the meteor- spects in cometary research. oid population by forcing to hyperbolic orbits. Svoren (2015) analyzes the brightenings of recurrent short- The experience and scientific data brought by the first Eur- period comets and investigates their correlation with the solar fi opean airborne meteor observation campaign are described by cycle. A statistically signi cant correlation cannot be found. Martin Vaubaillon et al. (2015) and Koten et al. (2015). The subject of et al. (2015) present an online facility to enhance the images of the investigation was the Draconids meteor storm observed, according cometary coma, the CometCIEF. Five enhancement techniques are to the earlier made theoretical prediction, on October 8, 2011. The offered as open source, namely the division by azimuthal average ρ airborne observation campaign involved two research dedicated or median and azimuthal renormalization, division by the 1/ aircraft flying in tandem over Scandinavia (mainly Finland). The profile, and radially variable spatial filtering. These image recorded outburst of the Draconids was a great and first oppor- enhancements help to distinguish the important coma features tunity to modern field-observing techniques to study the dust from the background. particles originated from the comet 21P (Giacobini-Zinner). Ejec- Results using imaging polarimetry are presented in three arti- ted particles survive in the comets dust stream for thousands of cles. Borisov et al. (2015) observed comet C/2013 R1 in the Bul- years. As part of a comet, this matter is among the most pristine garian National Astronomical Observatory Rozhen, and were able material known, and therefore is of extreme value to increase our to obtain spectropolarimetric maps close to the nucleus. Polar- knowledge of the physical and chemical conditions in the early ization was found to increase with wavelength, and depolarization Solar System. Many lessons were learned during the campaign was observed close to gas emission lines. Roy Choudhury et al. encouraging further airborne and space-based meteor observa- (2015) present imaging polarimetry of comets Lulin (C/2007 N3), tions which would escape dependency on weather and atmo- PANSTARRS (C/2011 L4), and 290P/Jager. Their results suggest that, spheric conditions. regarding linear polarization, Lulin could be classified as a so- The results of double-station meteor observations of the Per- called low-Pmax comet, and PANSTARRS as a high-Pmax comet. seid meteor shower conducted at the Institute of Astronomy of the With 290P/Jager, a polarimetric halo is found. Ivanova et al. (2015) Russian Academy of Sciences in 2012 and 2013 are presented by present polarimetric observations of comets C/2010 S1 and C/2010 Kartashova and Bolgova (2015). The shower is associated with the R1, done at 5.9–7 au heliocentric distances. Both comets showed Halley-type comet 109P (Swift-Tuttle). The authors obtain radi- activity beyond the water ice sublimation limit of 5 au. Non- ants, velocities, and orbital elements for 99 observed meteors. uniformity in the polarization distribution over the coma is Editorial / Planetary and Space Science 118 (2015) 1–7 5 found. Numerical modeling of the light scattering by the coma asteroids developed by Wilkman et al. (2015): the model is already particles was carried out using the superposition T-matrix method. utilized when simulated data are produced in order to facilitate Baratta et al. (2015) aim at testing the fidelity of laboratory the works by Cellino et al. (2015) and Muinonen et al. (2015) efforts in reproduction of space environments and processing of described above. Wilkman et al. carry out extensive ray-tracing astrophysical ices and residues. The authors present experimental computations for regolith models composed of closely-packed results from a study of organic residue that remains on the sub- spherical volume elements, taking into account the size distribu- strate following desorption of ice analogs of transneptunian objects tion of the elements. Their ray-tracing results are subsequently irradiated with Heþ ions. The residue is characterized by spectral presented for a discrete set of relevant regolith parameters, measurements from the UV to the far-infrared region. The changes allowing for an efficient interpolation both in parameters and in in spectra are tracked at 3 stages of sample transformation: after the angles required for the description of the surface-element deposition, irradiation and heating of the sample are also compared diffuse-reflection process. In the lightcurve computations, the with the spectra of the ultracarbonaceous Antarctic meteorites. The scattering model results in speeds fully comparable to those for substrates that retain the organic residues will be sent to the explicit, analytical scattering models. International Space Station, where they will be exposed to the Particular attention is paid to the slowly rotating asteroids. energetic particles and photons of the interplanetary medium. Marciniak et al. (2015) present the rationale for starting a dedicated These substrates will be returned and the observed changes will be photometric survey with the aim of reducing biases affecting dis- compared against controls maintained in several facilities. tributions of lightcurve parameters. A particular focus is main-belt asteroids with long rotation periods and/or small lightcurve 3.4. Asteroids amplitudes. Among the initial results from the survey is the reali- zation that about a quarter of the studied samples have rotation The asteroid research reported in the special issue focuses in on periods substantially different, typically longer, than what has been novel inverse methods for asteroid lightcurves, including also a widely accepted in the past. Fedorets and Granvik (2015) carry out fi physical, particulate-medium scattering model that can be ef - follow-up observations of one of the long-period Hungaria asteroids ciently, next-to-analytically utilized in lightcurve studies. Further detected by the Thousand Asteroid Light Curve Survey (TALCS; lightcurve analyses are reported in the contexts of spin and shape Masiero et al., 2009). An unsuccessful attempt to compute a convex biases and slowly rotating asteroids. Detailed physical character- shape model lead them to develop an indirect methodology for ization of asteroid surfaces is carried out in UV/blue spectroscopy identifying binaries and/or non-principal-axis rotators (NPA) based and in radar scattering. The asteroid section culminates in the on a photometric lightcurve. They conclude that, based on the asteroid collisions, dynamics, and surveys, as well as the near- TALCS detection statistics, it is likely that the Hungaria population Earth-object impact hazard. harbors a substantial fraction of long-period NPA rotators, and that Cellino et al. (2015), Muinonen et al. (2015), and Wang et al. follow-up observations aiming to correct the observational biases (2015) report novel lightcurve inversion methods and their affecting period distributions should focus on a sample that is applications to photometric observations of asteroids as well as to straightforward to debias such as the TALCS sample. simulated asteroid data. By utilizing the genetic inversion algo- As to asteroid spectroscopy, attention is paid to the space rithm adopted for the Gaia mission data-processing pipeline and weathering process that alters the targets' reflectance spectra. In the so-called Lommel–Seeliger ellipsoid (Muinonen and Lumme particular, Vilas et al. (2015) seek for Q- and O-type asteroids in 2015), Cellino et al. search for the best-fit solution for an asteroid's the S-complex that could show the spectral bluing in the spin and shape parameters based on sparse photometry. They 360–440 nm wavelengths, while the spectra in the visual and conclude that accounting for the surface-reflection coefficient near-infrared wavelengths is not yet noticeably affected by the properly improves the prospects of successfully retrieving the spin space-weathering process. They identify 54 main-belt asteroids and shape parameters. The Lommel–Seeliger ellipsoid refers to a triaxial ellipsoid with a Lommel–Seeliger surface reflection coef- suited for further study with a higher spectral resolution. ficient facilitating an analytical calculation of the disk-integrated Planetary radar provides one of the leading means for the brightness. physical characterization of near-Earth and main-belt objects. As For the statistical inverse problem concerning asteroid light- part of the ongoing studies in microwave scattering by near-Earth curves, Markov-chain Monte Carlo methods (MCMC) are intro- objects (NEOs) and main-belt objects. Virkki and Muinonen (2015) duced for the first time by Muinonen et al. (2015): these entail true provide a thorough geometric-optics study into the radar albedos MCMC methods that sample the a posteriori probability density of and circular-polarization ratios of boulders larger than the radar fl the unknowns as well as MCMC-powered methods for the geo- wavelength. For such boulders, the microwave signal can re ect metric characterization of the solution space of the un-knowns. As inside the objects and experience drastical polarization phenom- fi fl to the MCMC proposal probability density, novel approaches are ena due to the rst internal re ection. It is, nevertheless, con- offered with the help of virtual observations, that is, by introdu- cluded by the authors that reaching high radar albedos and high cing additional random noise in the observations in order to circular-polarization ratios requires multiple-scattering processes develop relevant proposals in MCMC sampling. Successful retrie- in the wavelength-scale in the interiors or on the surfaces of the vals of spins and shapes are reported for both sparse simulated asteroids. data and extensive real lightcurve data. Dell’Oro et al. (2015) analyze the ejection velocity fields of Wang et al. (2015) provide the spin and convex shape char- fragments produced in two hydrodynamical simulations to acteristics for the main-belt asteroids (362) Havnia and (506) understand whether there are some special properties needed to Marion, including uncertainty analyses based on virtual observa- trigger the process of re-accumulation of fragments formed in tions. They show that repeated optimization using the convex catastrophic collisions. Dell'Oro et al. find that a very important inversion method by, e.g., Kaasalainen et al. (2001), is feasible and role is played by the relation between the module of the ejection successfully maps the domains of spin and shape uncertainty. velocity and the distance from the irradiation point, but conclude The lightcurve inversion problem is further advanced by an that more extensive studies are needed to confirm that their efficient numerical particulate-medium scattering model for dark findings are applicable in general. 6 Editorial / Planetary and Space Science 118 (2015) 1–7

Galushina et al. (2015) assess the force model for asteroid in the initialization of ACM 2014, during their visit to Helsinki in (3200) Phaethon using metrics based on observed-minus- December 2007. The ACM 2014 was a most memorable conference. computed residuals and the Euclidian distance from a nominal trajectory. They conclude that, on the short term, it is safe to omit effects such as Yarkovsky and mass loss at perihelion. Emel'yanenko (2015) analyzes the orbital evolution of Table A1 fi Chelyabinsk-like test asteroids. Starting from the assumption that The Scienti c and Local Organizing Committees of ACM 2014. the Chelyabinsk impactor was on a sungrazing orbit about 1 Myr Scientific Organizing Committee Local Organizing Committee prior to the impact, Emel'yanenko shows that test asteroids starting on similar orbits have approximately a 75% probability for a solar collision and about a third of the remaining objects Prof. Karri Muinonen (Chair), Finland Dr. Antti Penttilä (Chair), Finland Dr. Mikael Granvik (Vice-Chair), Ms. Anne Virkki (Vice-Chair), Finland approach the Earth from the sunward side similar to the Chelya- Finland binsk impactor. Prof. Erik Asphaug, U.S.A. Mr. Grigori Fedorets (Secretary), Koschny and Busch (2015) describe hardware and software Finland used by the Teide Observatory Tenerife Asteroid Survey (TOTAS). Prof. Irina Belskaya, Ukraine Mr. Olli Wilkman (Webmaster), Finland TOTAS is both carrying out follow-up observations of new asteroid Prof. Richard Binzel, U.S.A. Dr. Tomas Kohout, Finland and Czech discoveries and used as a testbed for different survey strategies. Republic The authors list a number of points that can be utilized for opti- Dr. Hermann Boehnhardt, Germany Prof. Karri Muinonen, Finland mizing similar NEO surveys. Perna et al. (2015) review the activity Dr. William Bottke, U.S.A. Dr. Jouni Peltoniemi, Finland Prof. Peter Brown, Canada Dr. Mikael Granvik, Finland – fi and results of the NEOShield program they describe the scienti c Dr. Alberto Cellino, Italy Dr. Dagmara Oszkiewicz, Poland and strategic aspects of the asteroid impact hazard including the Dr. Guy Consolmagno, Vatican Dr. Jenni Virtanen, Finland latest estimates of impact consequences and highlight the next Dr. Björn Davidsson, Sweden Dr. Johannes Markkanen, Finland Dr. Ellen Howell, U.S.A. Dr. Maria Gritsevich, Finland and steps on the path towards an effective deflection capability for Russia planetary defense. Prof. Mikko Kaasalainen, Finland Ms. Hanna Pentikäinen, Finland Dr. Amy Mainzer, U.S.A. Ms. Julia Martikainen, Finland Dr. Patrick Michel, France Dr. Petr Pravec, Czech Republic 4. Conclusions Prof. Sho Sasaki, Japan Dr. Rita Schulz, The Netherlands The present special issue of Planetary and Space Science con- Prof. Gonzalo Tancredi, Uruquay fi Dr. Giovanni Valsecchi, Italy tains the rst part of regular peer-reviewed articles on the scien- Dr. Gorden Videen, U.S.A. tific advances made or initiated at the Asteroid, Comets, Meteors Prof. Xiaobin Wang, China conference in Helsinki, Finland, June 30–July 4, 2014. The second part of the articles will be published in the nearest future in another special issue of Planetary and Space Science. We look for- Appendix A ward to the next Asteroid, Comets, Meteors conference due to be organized in Montevideo, Uruguay, in spring 2017. See Table A1.

Acknowledgments References The Asteroids, Comets, Meteors conference in Helsinki in June 30–July 4, 2014 has been supported by the University of Helsinki, Andronikov, A., Andronikova, I., Hill, D., 2015. Impact history of the Chelyabinsk meteorite: electron microprobe and LA-ICP-MS study of sulfides and metals. Finnish Geodetic Institute (starting from 2015, Finnish Geospatial Planet. Space Sci. 118, 54–78. Research Institute, National Land Survey of Finland), European Baratta, G.A., Chaput, D., Cottin, H., Fernandez, L.C., Palumbo, M.E., Strazzulla, G., Space Agency (ESA), Gaia Research for European Astronomy 2015. Organic samples produced by ion bombardment of ices for the EXPOSE- – Training-network of the European Science Foundation (GREAT, R2 mission on the International Space Station. Planet. Space Sci. 118, 211 220. Borisov, G., Bagnulo, S., Nikolov, P., Bonev, T., 2015. Imaging polarime-try and ESF), Federation of Finnish Learned Societies, Polarisation as a tool spectropolarimetry of comet C/2013 R1 (Lovejoy). Planet. Space Sci. 118, to study the Solar System and beyond (European Union COST 187–192. Action MP1104), The Meteoritical Society, and the City of Helsinki. Campbell-Brown, M., 2015. A population of small refractory meteoroids in aster- oidal orbits. Planet. Space Sci. 118, 8–13. We are grateful to the authors and the reviewers of the papers Cellino, A., Muinonen, K., Hestroffer, D., Carbognani, A., 2015. Inversion of sparse in the PSS ACM 2014 special issue, as well as to Elsevier for fluent photometric data of asteroids using triaxial ellipsoid shape models and a processing of the special issue. The PSS special issue as well as the Lommel–Seeliger scattering law. Planet. Space Sci. 118, 221–226. Choudhury, S.R., Hadamcik, E., Sen, A.K., 2015. Study of some comets through ACM 2014 conference as a whole have been made possible by the imaging polarimetry. Planet. Space Sci. 118, 193–198. patient and solid support from the families of many of us involved DellOro, A., Cellino, A., Paolicchi, P., Tanga, P., 2015. Analysis of the kinematics of in the organizational activities. ejecta created after a catastrophic collision. Planet. Space Sci. 118, 285–295. Emel'yanenko, V., 2015. Dynamical evolution of Chelyabinsk-type bodies from We would like to express our gratitude to the ACM 2014 invited sungrazing orbits to near-Earth space. Planet. Space Sci. 118, 302–304. speakers in the plenary and parallel sessions, regular and poster Faggi, S., Codella, C., Tozzi, G.P., Comoretto, G., Crovisier, J., Nesti, R., Panella, D., speakers, attendees at large, chair persons of sessions, members of Boissier, J., Brucato, J.R., Bolli, P., Massi, F., Tofani, G., 2015. Search for ammonia – the Scientific Organizing Committee as well as members of the in comet C/2012 S1 (ISON). Planet. Space Sci. 118, 173 175. Fedorets, G., Granvik, M., 2015. Lightcurve analysis of asteroid (39420) Eliza- Local Organizing Committee, not forgetting a large number of bethgaskell and the possible excess of long-period non-principal-axis rotators students helping in the daily flow of the conference. in the Hungaria population. Planet. Space Sci. 118, 267–272. We are grateful to Dr. Edward Bowell (Lowell Observatory, Fernandez, J., Sosa, A., 2015. Jupiter family comets in near-Earth orbits: are some of them interlopers from the asteroid belt? Planet. Space Sci. 118, 14–24. Flagstaff, Arizona, USA) and Dr. Alan W. Harris (Jet Propulsion Galushina, T., Ryabova, G., Skripnichenko, P., 2015. The force model for asteroid Laboratory, Pasadena, California, USA) for their insightful guidance (3200) Phaethon. Planet. Space Sci. 118, 296–301. Editorial / Planetary and Space Science 118 (2015) 1–7 7

Guliyev, A., Nabiyev, S., 2015. The features of sporadic hyperbolic meteors observed Samarasinha, N., Mueller, B., Knight, M., Farnham, T., 2015. Results from the by television techniques in the period of 2007–2009. Planet. Space Sci. 118, worldwide coma morphology campaign for Comet ISON (C/2012 S1). Planet. 107–111. Space Sci. 118, 127–137. Hajdukova, M., Rudawska, R., Kornos, L., Toth, J., 2015. April Rho Cygnids and Comet Svoren, J., 2015. Distribution of brightenings of periodic comets during solar activity C/1917 F1 Mellish. Planet. Space Sci. 118, 28–34. cycles 9 to 22. Planet. Space Sci. 118, 176–180. Ivanova, O., Janna Dlugach, J., Afanasiev, V., Reshetnyk, V., Korsun, P., 2015. CCD Tomko, D., 2015. Modeling of a theoretical stream of comet 12P/Pons-Brooks. Pla- polarimetry of distant comets C/2010 S1 (LINEAR) and C/2010 R1 (LINEAR) at net. Space Sci. 118, 35–37. the 6-m telescope of the SAO RAS. Planet. Space Sci. 118, 199–210. Toth, J., Kornos, L., Zigo, P., Stefan Gajdos, S., Kalmancok, D., Vilagi, J., Simon, J., Janches, D., Hocking, W., Pifko, S., Hormaechea, J.L., Fritts, D.C., Brunini, C., Michell, Veres, P., Silha, J., Bucek, M., Galad, A., Rusnak, P., Hrabek, P., Duris, F., Rudawska, R., Samara, M., 2014. Interferometric meteor head echo observations using the R., 2015. All-sky Meteor Orbit System AMOS and preliminary analysis of three Southern Argentina Agile Meteor Radar. J. Geophys. Res. Space Phys. 119, unusual meteor showers. Planet. Space Sci. 118, 102–106. 2269–2287. Vaubaillon, J., Koten, P., Margonis, A., Toth, J., Rudawska, R., Gritsevich, M., Zender, J., Kaasalainen, M., Torppa, J., Muinonen, K., 2001. Optimization methods for asteroid McAuli e, J., Pautet, P.D., Jenniskens, P., Koschny, D., Colas, F., Bouley, S., Maquet, lightcurve inversion. II. The complete inverse problem. Icarus 153, 37–51. L., Leroy, A., Lecacheux, J., Borovicka, J., Watanabe, J., Oberst, J., 2015. The 2011 Kartashova, A.P., Bolgova, G.T., 2015. TV observations of the Perseid meteor shower Draconids: the first European airborne meteor observation campaign. Earth, in 2012–2013. Planet. Space Sci. 118, 120–126. Moon, Planets 114, 137–157. Kornos, L., Toth, J., Porubcan, V., Klacka, J., Nagy, R., Rudawska, R., 2015. On the Vilas, F., Hendrix, A.R., Jensen, E.A., 2015. The UV/blue effects of space weathering orbital evolution of the Lyrid meteoroid stream. Planet. Space Sci. 118, 48–53. manifested in S-complex asteroids II: probing for less-weathered objects in the Koschny, D., Busch, M., 2015. The Teide Observatory Tenerife Asteroid Survey. solar system. Planet. Space Sci. 118, 273–276. Planet. Space Sci. 118, 305–310. Virkki, A., Muinonen, K., 2015. Radar scattering by boulders studied using geo- Koten, P., Vaubaillon, J., Margonis, A., Toth, J., Duris, F., McAulli e, J., Oberst, J., 2015. metric optics. Planet. Space Sci. 118, 277–284. Double station observation of Draconid meteor outburst from two moving Wang, X., Muinonen, K., Wang, Y., 2015. Photometric analysis for the spin para- aircraft. Planet. Space Sci. 118, 112–119. meters and shapes of asteroids (362) Havnia and (506) Marion. Planet. Space Madiedo, J.M., 2015. Spectroscopy of a Rho-Cygnid fireball afterglow. Planet. Space Sci. 118, 242–249. Sci. 118, 90–94. Wilkman, O., Muinonen, K., Peltoniemi, J., 2015. Photometry of dark atmosphereless Marciniak, A., Pilcher, F., Oszkiewicz, D., Santana-Ros, T., Urakawac, S., Fauvaud, S., planetary bodies: an efficient numerical model. Planet. Space Sci. 118, 250–255. Kankiewicz, P., Tychoniec, L., Fauvaud, M., Hirsch, R., Horbowicz, J., Kaminski, K., Yanagisawa, M., 2015. Radiative characteristics of the Chelyabinsk superbolide. Konstanciak, I., Kosturkiewicz, E., Murawiecka, M., Nadolny, J., Nishiyama, K., Planet. Space Sci. 118, 79–89. Okumura, S., Polinska, M., Richard, F., Sakamoto, T., Sobkowiak, K., Stachowski, Zubko, E., Videen, G., Hines, D.C., Shkuratov, Y., Kaydash, V., Muinonen, K., Knight, G., Trela, P., 2015. Against the biases in spins and shapes of asteroids. Planet. M.M., Sitko, M.L., Lisse, C.M., Max Mutchler, M., Wooden, D.H., Li, J.-Y., Space Sci. 118, 256–266. Kobayashi, H., 2015. Comet C/2012 S1 (ISON) coma composition at 4 au from Markkanen, J., Penttilä, A., Peltoniemi, J., Muinonen, K., 2015. Inhomogeneous HST observations. Planet. Space Sci. 118, 138–163. particle model for light-scattering by cometary dust. Planet. Space Sci. 118, 164–172. Martin, M.P., Samarasinha, N., Larson, S., 2015. CometCIEF: a web-based image n enhancement facility to digitally enhance images of cometary comae. Planet. Karri Muinonen , Mikael Granvik Space Sci. 118, 181–186. Department of Physics, Gustaf Hällströmin katu 2a, P.O. Box 64, Masiero, J., Jedicke, R., Durech, J., Gwyn, S., Denneau, L., Larsen, J., 2009. The FI-00014 University of Helsinki, Finland – Thousand Asteroid Light Curve Survey. Icarus 204, 145 171. Finnish Geospatial Research Institute FGI, Geodeetinrinne 2, FI-02430 Michel, P., DeMeo, F.E., Bottke, W.F., 2015a. Asteroids IV. Space Science Series. University of Arizona Press, Tucson, Arizona. Masala, Finland Michell, R., Janches, D., Samara, M., Hormaechea, J.L., Brunini, C., Bibbo, I., 2015b. E-mail address: karri.muinonen@helsinki.fi (K. Muinonen) Simultaneous Optical and Radar Observations of Meteor Head-Echoes utilizing – SAAMER. Planet. Space Sci. 118, 95 101. Antti Penttilä Muinonen, K., Lumme, K., 2015. Disk-integrated brightness of a Lommel–Seeliger scattering ellipsoidal asteroid. Astron. Astrophys. 584 (A23), 1–6. Department of Physics, Gustaf Hällströmin katu 2a, P.O. Box 64, Muinonen, K., Penttilä, A., Granvik, M., Virkki, A., Fedorets, G., Wilkman, O., Kohout, FI-00014 University of Helsinki, Finland T. (Eds.), 2014. Asteroids, Comets, Meteors – Book of Abstracts, Helsinki, Fin- land, 2014 (ISBN 978-952-10-8962-6). Maria Gritsevich Muinonen, K., Wilkman, O., Cellino, A., Wang, X., Wang, Y., 2015. Asteroid lightcurve inversion with Lommel–Seeliger ellipsoids. Planet. Space Sci. 118, 227–241. Finnish Geospatial Research Institute FGI, Geodeetinrinne 2, FI-02430 Perna, D., Barucci, M.A., Drube, L., Falke, A., Fulchignoni, M., Harris, A.W., Harris, A. Masala, Finland W., Kanuchova, Z., 2015. A global response roadmap to the asteroid impact Institute of Physics and Technology, Ural Federal University, 620002 threat: the NEOShield perspective. Planet. Space Sci. 118, 311–317. Rudawska, R., Vaubaillon, J., 2015. Don Quixote – a possible parent body of a meteor Ekaterinburg, Russia shower. Planet. Space Sci. 118, 25–27. Rudawska, R., Matlovic, P., Toth, J., Kornos, L., 2015. Independent identification of meteor showers in EDMOND database. Planet. Space Sci. 118, 38–47.

n Corresponding author at: Department of Physics, Gustaf Hällströmin katu 2a, P.O. Box 64, FI-00014 University of Helsinki, Finland. Fax: þ358 2941 50610.