Thermal effects of late accretion to the crust and mantle of Mercury

Abstract

Impact bombardment on Mercury in the solar system late accretion phase (ca. 4.4 to 3.8 Ga) caused considerable mechanical, chemical and thermal reworking of its silicate reservoirs (crust and mantle). Depending on the frequency, size and velocity of such impactors, effects included regional and global scale crustal melting, and thermal perturbations of the mercurian mantle. We use a 3D transient heating model to test the effects of two bombardment scenarios on early (pre Tolstojan) Mercury mantle and crust. Results show that rare impacts by the largest (greater than 100 km diameter) bodies deliver sufficient heat to the shallow mercurian mantle producing high-temperature ultra-magnesian (komatiitic s.s.) melts. Impact heating leading to effusive (flood) volcanism can account for eponymous High-Magnesium Region (HMR) observed during the MErcury Surface, Space Environment, GEochemistry Ranging (MESSENGER) mission. We find that late accretion to Mercury induced volumetrically significant crustal melting (less than 58 vol.percent), mantle heating and melt production, which, combined with extensive resurfacing (less than 100 percent), also explains why its oldest cratering record was effectively erased, consistent with crater-counting statistics.

arXiv commentAccepted for publication in Earth and Planetary Science Letters

References in corpus (10)

• The origin of planetary impactors in the inner solar system
• A Sawtooth-like Timeline for the First Billion Year of Lunar Bombardment
• A new chronology for the Moon and Mercury
• A record of planet migration in the Main Asteroid Belt
• Our Sun. V. A Bright Young Sun Consistent with Helioseismology and Warm Temperatures on Ancient Earth and Mars
• The Fragility of the Terrestrial Planets During a Giant Planet Instability
• Late veneer and late accretion to the terrestrial planets
• The effects of the target material properties and layering on the crater chronology: the case of Raditladi and Rachmaninoff basins on Mercury
• Constraining the primordial orbits of the Terrestrial Planets
• Late accretion to the Moon recorded in zircon (U-Th)/He thermochronometry

Cited by in corpus (2)

• Modification of the composition and density of Mercury from late accretion
• Geoastronomy: Rocky planets as the Lavosier-Lomonosov Bridge from the non-living to the living world