Simplify the following text for a Grade 8 native English-speaking person.
Original: Temperatures on the surface have been estimated to lie between about â 20 Â C with the Sun overhead , dropping to about â ' 190 Â C at the winter pole .
Simplified: Temperatures on the surface have been thought to be between about -20 Â C with the Sun overhead , dropping to about -190 Â C at the winter pole .