6 urgent questions on the missing Titanic submersible

The Oceangate submersible Titan has been missing near the Titanic wreck site in the North Atlantic since early Sunday morning. There are a number of factors that will make any rescue or recovery incredibly difficult—including the remoteness of the area, the extreme depth of the site, and the fact that the five-person crew had 96 hours maximum of emergency air when they first descended. Their last communication was roughly 100 minutes after their descent. Unlike a submarine, which can sail in and out of ports on its own power, the...