TV Guide BBC World Service

In 1875 in the western Pacific, the crew of HMS Challenger discovered the Mariana Trench, which turned out to be deeper than Everest is high, by two kilometres. Trenches like Mariana form when one tectonic plate slips under another and heads down. Globally, there are about 50 of them. While at one time some thought it was too dark and deep for life exist and others wildly imagined monsters, the truth has turned out to be much more surprising. Misha Glenny and guests discuss the life and future of the world's deepest ocean trench

Ghazal Abbasi investigates how and why children in Pakistan are attending hospital and becoming HIV positive. With the help of a staff insider and undercover recording in the city's main hospital, Ghazal finds shocking lapses in medical protocol including the re-use of medicine vials and syringes