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Hello and welcome to the Witness History Podcast from the BBC World Service with me Rebecca

Keseby and today we go on an adventure to the very deepest, darkest place on planet Earth,

11 kilometers down to the bottom of the Pacific Ocean in the Mariana

trench.

I've been speaking to Don Walsh.

He was on the two-man crew that first went to the very bottom of the sea in 1960 in a specially designed sub called the Trieste.

released by the US Navy come these first films are The Batascape Trieste, rolling in heavy seas after the deepest dive ever

made by man. Jacques Picard and Lieutenant Walsh went down seven miles into the Marianas trench,

greatest known depth in the world.

It's hard to overestimate what an engineering triumph it was for Don Walsh and

Jacques Picard to get to the very bottom of the deepest oceanic trench and back up again

alive in January 1960. It wasn't just the first manned

mission, it was the first ever mission. No one and nothing had been sent that

far down before and no one knew for sure if their equipment could take it.

My understanding is that you're looking at about 16,000 pounds per square inch of pressure. Eight tons. Eight tons. So the total pressure on the

cabin I think we figured was 200,000 tons. What would happen to a human being if they were exposed to that pressure?

...