Some general motivation
Planets grow from planetesimals, which grow from smaller solid particles in a primarily gaseous nebula. Over the several Myr duration of planetesimal formation, indicated by primitive meteoritcal, asteroidal and cometary properties, solids decouple significantly from the nebula gas.
The thermal, dynamical and collisional histories of these objects are important for the understanding of planetary system formation scenarios. The record for the evolution of these planetary "building blocks" may be interwoven in the profiles of nowadays small bodies of various sizes and source regions.
Thermal and Structural Evolution of Small Solar System Bodies
The designation "small bodies" in Solar System studies refers to astronomical bodies smaller than planets, for which the Sun is the main gravitational attractor. The diversity in the dynamical properties of these bodies may be a result of the specific accretion locations of each class of bodies, or their subsequent orbital evolution, mainly due to gravitational perturbations by the planets. There are many dynamical classes of small bodies, but the ones that share a common dynamical evolution scheme, or a widely accepted chain of origin, are JFCs (Jupiter family comets), Centaurs and trans-Neptunian objects.
Starting in my thesis work and continuing ever since, I study the thermo-chemical evolution of such small bodies. This is done through both analytical and numerical studies, solving different configurations of heat and mass transfer equations for a porous multi-component nucleus, including self-consistent schemes for the interior and exterior boundary conditions and phase transition and thermodynamics of various ice species and refractory components.
We applied our general thermal evolution code several cases, which represent a sample of the various physical characteristics of the different populations:
- For trans-Neptunian objects, we find a general trend of more compacted, thermally-processed and volatile-depleted interiors, with increasing size and bulk density. The sub-surface composition is found to promote a sometimes intricate mixture of volatile compounds. The deep interior of larger objects is found to have relatively viable conditions for liquid phases, although the longevity and robustness of this is still examined.
- For Centaur objects, we set various scenarios for the succession of Centaur origin and emplacement - Either as 'a chip of the old block' of larger trans-Neptunian objects, which scattered inwards, or as a 'rolling stone' from out beyond Neptune, which leisurely diffused inwards. We found it possible to distinguish between degrees of thermo-chemical processing based on dynamical features and origin, but this is limited to the sub-surface. Consequently, composition differences between different Centaurs, as revealed by surface photometry and spectroscopy, should be the result of relatively recent thermal evolution, rather then a consequence of different initial states. The end results of these sets of simulations should provide insight into the current internal state of Centaurs and the initial configurations of evolving Jupiter-family comet nuclei.
- In the case of comets we examined in detail the internal evolution, dust activity and gas emission, through quasi-3D modeling and comparison to a slew of observational data. The outstanding feature emerging from the our simulations is that even at relatively high cometocentric latitudes the nucleus will develop a complex pattern of volatile stratification with depth. We also find that combining either multi-epoch single-component or single-epoch multi-species observations with high-resolution numericla modeling of the activity, yields useful constraints on the interior structure and composition.
Analysis of activity patterns in comets
Text coming soon.
Modeling target objects for space missions and observations
Text coming soon.
Dynamical behavior of planet-crossing objects (e.g., Centaurs, near-Earth objects)
Text coming soon.
Early evolution beyond the snow line (under various nebula conditions)
Text coming soon.
Hydrodynamical simulation of planetesimal formation processes
Text coming soon.
Research methodologies in astrobiology
The Drake equation (in its current formulation) is a scheme used to estimate the number of detectable intelligent aliens around us. It does so by collecting together what is considered as the leading terms that represent what we know about astronomy, planetary science, biological evolution and social development. However, after ~50 years of rapid scientific progress, much of what we have discovered challenges us to either improve our estimates of the factors in Drake's equation, re-work the equation according to current knowledge in the field of astrobiology, or change the question that we are asking and the way we ask them altogether.
Analysis of mixed microbial populations
The temperature response and energy metabolism of a given environmental microbial community may be understood as a combination of different populations of micro-organisms and their processing rates. Such a mixed community response can be treated as a sum of processes from psychrophilic, psychrotolerant, mesophilic, and thermophilic population adaptations. In this work we attmept to evaluate different mathematical approaches in order to model microbial respiration curves of single and complex microbial communities. This can could potentially contribute to the interpretation of environmental temperature responses and help to elucidate the nature and function of microorganisms in deep subsurface habitats.
Collaborators list:
- Karen Meech, Inst. for Astronomy & NASA Astrobiology Inst., University of Hawai'i.
- Bin Yang, Inst. for Astronomy & NASA Astrobiology Inst., University of Hawai'i.
- Alberto Robador, Dept. of Oceanography & NASA Astrobiology Inst., University of Hawai'i.
- Stephen Freeland, Inst. for Astronomy & NASA Astrobiology Inst., University of Hawai'i.
- Jeff Taylor, Hawai'i Inst. of Geophysics & Planetology, University of Hawai'i.
- Dina Prialnik, Dept. of Geophysics & Planetary Sciences, Tel Aviv University.
- Ravit Helled, Dept. of Geophysics & Planetary Sciences, Tel Aviv University.
- Steven Desch, School of Earth & Space Exploration, Arizona State University.
- Rosario Brunetto, Inst. d'Astrophysique Spatiale, Université Paris-Sud, Orsay.
- Francesca DeMeo, Dept. of Earth, Atmospheric & Planetary Sciences, MIT.
- Mario Melita, Inst. de Astronomía y Física del Espacio (IAFE), UBA-CONICET.
- Patryk Lykawka, Astronomy group, Faculty of Social & Natural Sciences, Kinki University.
- Jade Bond, Dept. of Astrophysics, University of New South Wales.
- Aurelie Guilbert, Dept. of Earth & Space Sciences, UCLA.
- Nader Haghighipour, Inst. for Astronomy, University of Hawai'i.