Simplify the following text for a Grade 10 native English-speaking person.
Original: It was initially thought that the dark region might be a lake of a fluid or at least tar-like substance , but it is now clear that Huygens landed on the dark region , and that it is solid without any indication of liquids .
Simplified: It was at first thought that dark areas near the center of Titan could be a lake of a liquid or tar-like substance , but the probe landed on the dark area , and it is solid without any liquid .