Complex sentence: The spacecraft returned data for 224 seconds during its descent through the Martian atmosphere, however at 09:11:05 UTC, with the spacecraft about to fire its retrorockets in preparation for landing, all contact was lost.
Split into simpler sentences: The spacecraft returned data for 224 seconds during its descent through the Martian atmosphere. However, at 09:11:05 UTC, with the spacecraft about to fire its retrorockets in preparation for landing, all contact was lost.