Asteroids fail to retain cometary impact signatures

Abstract

A bombardment of comets is thought to have occurred in the inner solar system as a result of a dynamical instability among the giant planets after gas disk dispersal. Vesta, the second largest asteroid in the main asteroid belt, likely differentiated before gas disk dispersal, implying its crust witnessed the cometary bombardment. The composition of HED meteorites, which represent fragments of Vesta's crust, could therefore have been altered by cometary impacts. Here we combine noble gas mass spectrometry measurements, N-body simulations, collision rate calculations, and impact simulations to estimate the cometary contribution to Vesta. While our dynamical simulations indicate that Vesta likely underwent a significant number of collisions with large comets, we find no xenon cometary signature in HED meteorites. This apparent contradiction arises due to the fact that cometary impacts were at high speeds and Vesta's weak gravitational attraction made it incapable of retaining cometary material. Smaller asteroids are even less likely to retain such material. Therefore, if a cometary xenon signature is ever detected in an asteroid belt object, it must have been acquired during formation, within the same source region as comet 67P/Churyumov-Gerasimenko, and have been implanted later into the asteroid belt.

References in corpus (20)

• Dynamical Evolution of the Early Solar System
• Origin of water in the inner Solar System: Planetesimals scattered inward during Jupiter and Saturn's rapid gas accretion
• The timeline of the Lunar bombardment - revisited
• Asteroid family ages
• Mars' Growth Stunted by an Early Giant Planet Instability
• Neptune's Orbital Migration Was Grainy, Not Smooth
• Dynamical evidence for an early giant planet instability
• Onset of giant planet migration before 4480 million years ago
• The thermal, mechanical, structural, and dielectric properties of cometary nuclei after Rosetta
• Secular resonance sweeping of the main asteroid belt during planet migration
• Early Solar System instability triggered by dispersal of the gaseous disk
• Early Bombardment of the Moon: Connecting the Lunar Crater Record to the Terrestrial Planet Formation
• Instabilities in the Early Solar System due to a Self-gravitating Disk
• The composition of Solar system asteroids and Earth/Mars moons, and the Earth-Moon composition similarity
• Born extra-eccentric: A broad spectrum of primordial configurations of the gas giants that match their present-day orbits
• The Dissipation of the Solar Nebula Constrained by Impacts and Core Cooling in Planetesimals
• A race against the clock: Constraining the timing of cometary bombardment relative to Earth's growth
• An early giant planet instability recorded in asteroidal meteorites
• The late accretion and erosion of Vesta's crust recorded by eucrites and diogenites as an astrochemical window into the formation of Jupiter and the early evolution of the Solar System
• Crash Chronicles: relative contribution from comets and carbonaceous asteroids to Earth's volatile budget in the context of an Early Instability