Cometary Science Newsletter

January 2021
Michael S. P. Kelley (

PhD and Postdoc position in comet/asteroid science at the TU Braunschweig (Germany)

Applications are invited for one PhD and two postdoc positions in comet/asteroid science at the TU Braunschweig. Details on the positions and the application process can be found under the following links:

Refereed Articles

Abstracts of articles in press or recently published. Limited to 3000 characters.

Interplanetary Nanodust as a Final Stage of Evolution of the Solid Substance of Small Bodies of the Solar System

  • Simonia, I. 1
  • Nabiyev, Sh. 2
  1. School of Natural Sciences and Medicine, Ilia State University
  2. School of Earth and Space Exploration, Arizona State University

In this paper, the processes of nanometric dust formation in the Solar System and interactions of nanodust with external factors and forces, are considered. The mechanisms of zodiacal dust luminescence, the concept of unidentified interplanetary lines and the possible presence of nano-diamond dust are proposed. Other aspects of the problem are also discussed, including the nanodust’s resonance absorption of the solar radiation.

Planetary and Space Science (Published)

DOI: 10.1016/j.pss.2020.105096 NASA ADS: 2020P&SS..19405096S

Modelling heterogeneous dust particles. An application to cometary polarization

  • Halder, P. 1
  • Ganesh, S. 1
  1. Astronomy and Astrophysics Division, Physical Research Laboratory, Ahmedabad, India.

In this work, we introduce a comet dust model that incorporates multiple dust morphologies along with inhomogeneous mixture of silicate minerals and carbonaceous materials under power-law size distribution, to replicate the standard polarization-phase curve observed in several comets in the narrow-band continuum. Following the results from Rosetta/MIDAS and COSIMA, we create high porosity Hierarchical Aggregates (HA) and low porosity (< 10%) Solids in the form of agglomerated debris. We also introduce a moderate porosity structure with solids in the core, surrounded by fluffy aggregates called Fluffy Solids (FS). We study the mixing combinations, (HA and Solids), (HA and FS) and (HA, FS and Solids) for a range of power-law index n=2.0 to 3.0 for different sets of mixing percentage of silicate minerals and carbonaceous materials. Polarimetry of the short period comets 1P/Halley and 67P/Churyumov-Gerasimenko match best with the polarisation resulting from the combination of HA and Solids while the combinations (HA and FS) and (HA, FS and Solids) provide the best fit results for the long period comets C/1995 O1 (Hale-Bopp) and C/1996 B2 (Hyakutake). The best fit model results also recreate the observed wavelength dependence of polarization. Our dust model agree with the idea that the long period comets may have high percentage of loose particles (HA and FS) compared to those in the case of short period comets as the short period comets experience more frequent and/or higher magnitude of weathering.

Monthly Notices of the Royal Astronomical Society (In press)

DOI: 10.1093/mnras/staa3647 NASA ADS:  2020MNRAS.tmp.3420H arXiv: 2011.08252

P/2019 LD2 (ATLAS): An Active Centaur in Imminent Transition to the Jupiter Family

  • Steckloff, J. K. 1,2
  • Sarid, G. 3
  • Volk, K. 4
  • Kareta, T. 4
  • Womack, M. 5
  • Harris, W. 4
  • Woodney, L. 6
  • Schambeau, C. 5
  1. Planetary Science Institute, Tucson, AZ, USA
  2. University of Texas at Austin, Austin, TX, USA
  3. SETI Institute, Mountain View, CA, USA
  4. University of Arizona, Tucson, AZ, USA
  5. Florida Space Institute, University of Central Florida, Orlando, FL, USA
  6. California State University, San Bernardino, CA, USA

The recently discovered object P/2019 LD2 (by the Asteroid Terrestrial-impact Last Alert System) was initially thought to be a Jupiter Trojan asteroid, until dynamical studies and the appearance of persistent cometary activity revealed that this object is actually an active Centaur. However, the dynamical history, thermal environment, and impact of such environments on the activity of 2019 LD2 are poorly understood. Here we conduct dynamical simulations to constrain its orbital history and resulting thermal environment over the past 3000 yr. We find that 2019 LD2 is currently in the vicinity of a dynamical “Gateway” that facilitates the majority of transitions from the Centaur population into the Jupiter Family of Comets (JFC population). Our calculations show that it is unlikely to have spent significant amounts of time in the inner solar system, suggesting that its nucleus is relatively pristine in terms of physical, chemical, and thermal processing through its history. This could explain its relatively high level of distant activity as a recently activated primordial body. Finally, we find that the median frequency of transition from the Gateway population into the JFC population varies from once every ∼3 yr to less than once every 70 yr, if 2019 LD2ʼs nucleus is ∼1 km in radius or greater than 3 km in radius. Forward modeling of 2019 LD2 shows that it will transition into the JFC population in 2063, representing the first known opportunity to observe the evolution of an active Centaur nucleus as it experiences this population-defining transition.

The Astrophysical Journal Letters (Published)

DOI: 10.3847/2041-8213/abc888 NASA ADS: 2020ApJ...904L..20S arXiv: 2008.02943