Simplify the following text for a Grade 11 native English-speaking person.
Original: The radius of the parent asteroid was probably about 89 km , only slightly larger than that of Himalia , which retains approximately 87 % of the mass of the original body .
Simplified: The radius of the parent asteroid was probably about 89 km , only a bit bigger than that of Himalia , which retains approximately 87 % of the mass of the original body .