Impacts may provide heat for aqueous alteration and organic solid formation on asteroid parent bodies

Minami Yasui,Taku Tazawa,Kazunori Ogawa,Masahiko Arakawa,Ryohei Hashimoto

doi:10.1038/s43247-021-00159-x

Abstract

Chemical reactions on asteroid parent bodies, such as aqueous alteration and the formation of organic solids, require a heat source. Radioactive decay in the interiors of these bodies is generally considered the most important heat source, but impact-generated heating is also likely to play a role. Here we present high-velocity impact cratering experiments using thermocouples embedded in the target material to directly measure the spatial and temporal evolution of temperature throughout each impact experiment. We find that the maximum temperature below the crater floor scales with the distance from the impact point, while the duration of temperature rise is scaled by the thermal diffusion time. We use numerical modelling to suggest that, at distances within 2 astronomical units, impacts producing craters of >20 km radius can facilitate aqueous alteration in the material below the crater, while those which produce craters of 1 km radius can support organic solid formation.

Highlights

Chemical reactions on asteroid parent bodies, such as aqueous alteration and the formation of organic solids, require a heat source
Aqueous alteration may have occurred in the parent bodies by the heating of 26Al in the early history of the solar system, the efficiency of 26Al heating might depend on the timing of the accretion of the parent bodies[4]
The relative velocity among asteroids in the main asteroid belt is estimated to be 4–5 km s−1 6, so high shock pressure would have been induced by their collision, and the associated shock heat would have raised the temperature around an impact crater instantaneously. These mutual collisions among small bodies are a common phenomenon throughout the history of the solar system, so impact heating is a possible candidate for the heat sources, and could have continued as a heat source even after the radioactive heating by 26Al ceased

Summary

Introduction

Chemical reactions on asteroid parent bodies, such as aqueous alteration and the formation of organic solids, require a heat source. The relative velocity among asteroids in the main asteroid belt is estimated to be 4–5 km s−1 6, so high shock pressure would have been induced by their collision, and the associated shock heat would have raised the temperature around an impact crater instantaneously. These mutual collisions among small bodies are a common phenomenon throughout the history of the solar system, so impact heating is a possible candidate for the heat sources, and could have continued as a heat source even after the radioactive heating by 26Al ceased. The effects of impact heating have not been directly studied, there have been many numerical simulations on the effects of impact heating[10,11]

Methods

Results

Conclusion