Delivery of organics to Mars through asteroid and comet impacts

Abstract

Given rapid photodissociation and photodegradation, the recently discovered organics in the Martian subsurface and atmosphere were probably delivered in geologically recent times. Possible parent bodies are C-type asteroids, comets, and interplanetary dust particles (IDPs). The dust infall rate was estimated, using different methods, to be between $0.71$ and $2.96\times 10^6$ kg/yr (Nesvorny et al., 2011, Borin et al., 2017, Crismani et al., 2017); assuming a carbon content of 10% (Flynn, 1996), this implies an IDP carbon flux of $0.07-0.3\times 10^6$ kg/yr. We calculate for the first time the carbon flux from impacts of asteroids and comets. To this end, we perform dynamical simulations of impact rates on Mars. We use the N-body integrator RMVS/Swifter to propagate the Sun and the eight planets from their current positions. We separately add comets and asteroids to the simulations as massless test particles, based on their current orbital elements, yielding Mars impact rates of $4.34\times 10^{-3}$ comets/Myr and 3.3 asteroids/Myr. We estimate the global carbon flux on Mars from cometary impacts to be $\sim 0.013\times 10^6$~kg/yr within an order of magnitude, while asteroids deliver $\sim 0.05\times 10^6$~kg/yr. These values correspond to $\sim 4-19\%$ and $\sim 17-71\%$, respectively, of the IDP-borne carbon flux estimated by Nesvorny et al. 2011, Borin et al. 2017 and Crismani et al. 2017. Unlike the spatially homogeneous IDP infall, impact ejecta are distributed locally, concentrated around the impact site. We find organics from asteroids and comets to dominate over IDP-borne organics at distances up to 150~km from the crater center. Our results may be important for the interpretation of in situ detections of organics on Mars.

arXiv comment30 pages, 5 figures, accepted for publication in Icarus

References in corpus (8)

• Density of asteroids
• Main Belt Asteroids with WISE/NEOWISE I: Preliminary Albedos and Diameters
• The taxonomic distribution of asteroids from multi-filter all-sky photometric surveys
• Dynamical Model for the Zodiacal Cloud and Sporadic Meteors
• The contamination of the surface of Vesta by impacts and the delivery of the dark material
• Amino Acids in Comets and Meteorites: Stability under Gamma Radiation and Preservation of Chirality
• Olivine on Vesta as exogenous contaminants brought by impacts: Constraints from modeling Vesta's collisional history and from impact simulations
• The primordial collisional history of Vesta: crater saturation, surface evolution and survival of the basaltic crust

Cited by in corpus (4)

• Exogenous delivery of water to Mercury
• Mars' atmospheric neon suggests volatile-rich primitive mantle
• Enrichment of the HR 8799 planets by minor bodies and dust
• Mars: new insights and unresolved questions