A massive search-and-rescue mission is racing against the clock to find a tourist submersible that disappeared in deep water off the coast of south-eastern Canada. It embarked on an expedition on June 18 to see the wreck of the Titanic, but lost contact with its support vessel less than two hours after its departure. To take a closer look at what we know so far, we're joined by Jamie Pringle, a reader in forensic geoscience at Keele University in the UK, as well as our Science Editor Julia Sieger.
