Simplify the following text for a Grade 12 native English-speaking person.
Original: Like Mathilde , its density appears to be unusually low , indicating that it may be a loosely-packed rubble pile ( an asteroid that has been broken apart by a collision and pulled back together by gravity ) .
Simplified: Like Mathilde , its density appears to be unusually low , indicating that it may be a loosely-packed rubble pile , not a monolithic object .