Complex sentence: Vesta surface shows no significant trace of nanophase iron because the impact speed on Vesta are too low to make rock melting and vaporization an appreciable process-instead the regolith evolution is dominated by brecciation and subsequent mixing of bright and dark components.
Split into simpler sentences: Vesta surface shows no significant trace of nanophase iron because the impact speeds on Vesta are too low to make rock melting and vaporization an appreciable process. Instead, regolith evolution is dominated by brecciation and subsequent mixing of bright and dark components.