DRIVING ON THE HIGHWAY AS A COLD FRONT APPROACHED, OUTSIDE TEMPERATURE DROPPED TO 17 DEGREES. ALL OF A SUDDEN WE HEARD A LOUD SOUND, LIKE A GUNSHOT AND IMMEDIATELY GLASS FELL ON OUR HEADS. THE SUNROOF HAD EXPLODED FOR NO APPARENT REASON AS THERE WERE NO OTHER VEHICLES AROUND US. IT WAS A SCARY INCIDENT WITH MY FAMILY ONBOARD. ONLY MINOR GLASS CUTS WERE SUFFERED, MOSTLY ON THE HANDS AND WE WIPED THE GLASS PIECES OFF OURSELVES. OUR DRIVING SPEED WAS APPROXIMATELY 75 MILES/HOUR, THROUGH OPEN FIELDS (NO BUILDINGS OR CONSTRUCTION NEARBY) ON A STRAIGHT STRETCH OF HIGHWAY.