CHADRILL is a deep drilling project in Chad that plans to recover a continuous sediment core from Lake Chad, spanning the Miocene through the Pleistocene. The long record will reveal how North Africa’s hydroclimate changed under different climate conditions, including higher greenhouse gases and the absence of large Northern Hemisphere ice sheets, and how orbitally driven climate cycles shaped the lake’s history. By pinning down the age and origin of Lake Chad and tracking its size and water chemistry over time, researchers hope to explain why the lake now sits in a desert. The Chad Basin is rich in early hominid fossils, so the climate history could shed light on how environmental shifts influenced human evolution and migrations across northern Africa. In addition, the sediments may serve as an analogue for ancient lake systems on Mars, and the project will also explore the subsurface biosphere preserved in these layers.