Unknown Terrain, Low Oxygen: Challenges As Hunt For Titanic Sub Continues

Asubmersiblevessel taking tourists on a deep ocean journey to view the wreckage of theTitanichas been missing since Sunday. One pilot and four passengers are aboard.

A submersible vessel taking tourists on a deep ocean journey to view the wreckage of the Titanic has been missing since Sunday. One pilot and four passengers are aboard.

Here is a look at the situation as rescuers search an area the size of the state of Connecticut -- or about half the size of Belgium -- for the submersible, which could be on the ocean floor or bobbing on the surface, with the tourists bolted in from the outside.

The vessel's oxygen supply will run out early on Thursday, according to OceanGate, the private company that operates the tour.

INHOSPITABLE TERRAIN