Perspectives on Comets, Comet-like Asteroids, and Their Predisposition to Provide an Environment That Is Friendly to Life

Abstract

In recent years, studies have shown that there are many similarities between comets and asteroids. In some cases, it cannot even be determined to which of these groups an object belongs. This is especially true for objects found beyond the main asteroid belt. Because of the lack of comet fragments, more progress has been made concerning the chemical composition of asteroids. In particular, the SMASSII classification establishes a link between the reflecting spectra and chemical composition of asteroids and meteorites. To find clues for the chemical structure of comets, the parameters of all known asteroids of the SMASSII classification were compared to those of comet groups like the Encke-type comets, the Jupiter-family comets, and the Halley-type comets, as well as comet-like objects like the damocloids and the centaurs. Fifty-six SMASSII objects similar to comets were found and are categorized as comet-like asteroids in this work. Aside from the chemistry, it is assumed that the available energy on these celestial bodies plays an important role concerning habitability. For the determination of the available energy, the effective temperature was calculated. Additionally, the size of these objects was considered in order to evaluate the possibility of a liquid water core, which provides an environment that is more likely to support processes necessary to create the building blocks of life. Further study of such objects could be notable for the period of the Late Heavy Bombardment and could therefore provide important implications for our understanding of the inner workings of the prebiotic evolution within the Solar System since the beginning.

About Exobiology: The Case for Dwarf K Stars

“…Thereafter, they could have migrated into the CLI-HZs when their host stars had become older and less active. Another possibility is that the planets could have lost their original atmospheres and water inventories at a much later time (ages > 2 Gyr), outgassed and/or captured water and gases from collisions with icy bodies (i.e., exocomets) (e.g., Bosiek et al 2016). It is also possible that some planets could have been protected by strong geomagnetic fields, shielding them from the expected strong X-ray-UV radiation and winds from their host stars when those were young and highly active (e.g., Khodachenko et al 2007;Erkaev et al 2013).…”

Case Studies of Exocomets in the System of HD 10180

“…Studies about exocomets yield a large range of implications, involving the origin, structure and evolution of systems as well as the proliferation of water and prebiotic compounds to terrestrial planets, which will increase their chances of being habitable. This latter aspect has been showcased by results from Rosetta (e.g., Capaccioni et al 2015;Rickman et al 2015;Bosiek et al 2016), which indicate the pivotal role of comets regarding prebiotic chemistry and potential exobiology.…”

“…A highly significant aspect is that exocomets are able to deliver both liquid water and basic organic substances from regions beyond the snowline to the inner domains of star-planet systems where terrestrial planets with features in supportive to habitability reside; see, e.g., observational results and analyses for 67P/Churyumov-Gerasimenko by Capaccioni et al (2015) and Rickman et al (2015) based on Rosetta. Recently, Bosiek et al (2016) argued that the ability of comets and comet-like asteroids to foster prebiotic chemistry as well as their available energy may be relevant for facilitating habitability in various exosolar systems.…”