Amna Nawaz:

The submersible vanished on Sunday during a deep sea tour of the Titanic shipwreck, the watery grave of one of the worst ocean disasters in the 20th century.

The Titan, roughly the size of a minivan, set off with about four days' worth of breathable oxygen. Officials say that is enough to last until tomorrow morning.

For the international search-and-rescue operation the clock is ticking and the pressure growing. Several countries are bringing in additional surface ships and underwater vessels to aid the effort. Canadian ships have dropped sonar buoys to detect any underwater sounds in the search area about 400 miles off the southern coast of Newfoundland.

And following reports of the noise, French researchers dispatched an unmanned robotic vehicle set to arrive this evening capable of hooking the sup to a cable that could tow it to the surface.

Jules Jaffe is an oceanographer at the Scripps Institution.

Jules Jaffe, Research Oceanographer, Marine Physical Laboratory, Scripps Institution of Oceanography: The ocean is inherently a noisy place. We have lots of marine mammals making sounds. And there's a lot of instrumentation in the ocean there, geophysical explorations going on.

Sound travels pretty well underwater, and so I would give it a low chance of identification that, in fact, the banging noises that we heard were from the underwater submersible.

ncG1vNJzZmivp6x7sa7SZ6arn1%2Bjsri%2Fx6isq2ejnby4e8yoqZ5lo522sb%2BMnqiuoaCisq%2FAjKOmoqaZo7Ruv8SaqZygXZu8s3nMoqqsoZ6cerTBwWaYn6yVp3qzsc%2Boqa2rXaSzbq7Ap56ippdiu7C10p6q