Is all "dark tourism" immoral? A submersible that promised five wealthy tourists a tour of the Titanic has gone missing in the deep, with little hope of return. Some say it encapsulates the ills of our obsession with tragedy.
Race against time to rescue lost Titanic sub
Deadly depths: Contact with the sub was lost just one hour and 45 minutes into its descent to the wreck site. Glossary
Titanic - The RMS Titanic was the largest ship afloat at the time and it is the deadliest cruise ship disaster in history.
Chernobyl - The disaster, in 1986, involved a meltdown at a nuclear plant in Ukraine.
Fukushima - A prefecture in Japan that was the site of a nuclear powerplant meltdown in 2011. An exclusion zone around the nuclear power plant still exists ten years after the disaster.
Pompeii - A Roman town in Italy. It was buried under ash after a nearby volcano erupted. The ash preserved the town so well that today people can walk through the streets and into some buildings.
CEO - The Chief Executive Officer is the highest ranking person in a company. They are responsible for making decisions about the company's future.
Macabre - Gruesome or ghastly.
Auschwitz - Nazi death camp where over a million people lost their lives during WW2.
Turkmenistan - A country in Central Asia with a population of 6.3 million.
Soviet - Relating to the Soviet Union, a powerful group of communist republics, the biggest being Russia, that existed from 1922 to 1991.
Pripyat - A city in northern Ukraine that has been abandoned since 1986, due to the Chernobyl nuclear disaster.
Middle Ages - The Middle Ages was the period in European history that came between ancient and modern times. It lasted from about 500 to about 1500.
Gulags - Forced labour camps established by Joseph Stalin in the Soviet Union, housing both small-time criminals and political prisoners.