Complex sentence: However, when the fragments of the massive lump of rock were found, only 1.3 tonnes remained, meaning that around 97% of the meteorite had vaporised on its descent, during which the meteor finally exploded with around 1.7 kilotons of energy.
Split into simpler sentences: However, when the fragments of the massive lump of rock were found, only 1.3 tonnes remained, meaning that around 97% of the meteorite had vapourised on its descent. On its descent, the meteor finally exploded with around 1.7 kilotons of energy.