Challenger Deep - Mariana Trench

The deepest spot in Earth's oceans was discovered March 23, 1875 by the survey ship HMS Challenger of the British Royal Navy.  At the time, the Challenger Deep was measured as 26,850 feet below the surface of the ocean.  Later measurements in 1951, using sound waves via echo sounding, placed the depth at 35,761 feet.  Depth measurements by submersibles have placed the depth between 35,786 feet and 35,814 feet.

The first manned descent to the Challenger Deep was in 1960, by Jacques Piccard and Don Walsh in the Trieste.  The Trieste spent nearly twenty minutes at depth before returning to the surface due to concerns regarding sediment stirred up as they approached the bottom and a crack that had developed in one of Trieste's windows.

Since 1960, no one human has returned to the Challenger Deep.  In comparison, the United States have landed 12 men on the moon in that time.  On March 25 according to twitter, this has apparently changed....

I only tweet when I have something worth saying. Today is the culmination of a 7 yr project. It's finally dive day. Follow us @deepchallenge
— James Cameron (@JimCameron) March 24, 2012

Director James Cameron has commenced his dive to the Challenger Deep.  Upon reaching the bottom, he would become the first person to reach the Challenger Deep alone.

"RELEASE, RELEASE, RELEASE!" @jimcameron's last words before starting the descent to the Mariana Trench #deepseachallenge
— DeepSea Challenge (@DeepChallenge) March 25, 2012

Moments before the beginning of the descent, the anticipation and excitement of the task at hand must have been intense.

.@jimcameron just passed the #Titanic depth at around 4,305 meters #deepseachallenge
— DeepSea Challenge (@DeepChallenge) March 25, 2012

There are numerous milestones that are reached as Cameron descends to the bottom, including passing the depth of the Titanic in the North Atlantic.  Of course, Titanic sank one hundred years ago this coming April and James Cameron directed the movie Titanic in 1997.

Just arrived at the ocean's deepest pt. Hitting bottom never felt so good. Can't wait to share what I'm seeing w/ you @deepchallenge
— James Cameron (@JimCameron) March 25, 2012

When someone has gone through the mentally and physically tasking hours of reaching the Challenger Deep, it must be quite a feeling.

.@jimcameron is the first person in history to solo dive to the deepest place on Earth, a record 35,756ft/10,898m #deepseachallenge
— DeepSea Challenge (@DeepChallenge) March 25, 2012

James Cameron has earned his placed in the record books as the third person ever to reach the deepest place in Earth's oceans when confirmed.

.@jimcameron has surfaced! Congrats to him on his historic solo dive to the ocean's deepest point #deepseachallenge
— DeepSea Challenge (@DeepChallenge) March 26, 2012

Indeed congratulations.  What will be interesting in the next few days or weeks, will be what pictures, videos or samples he has been able to return to the surface with.  It is an interesting time!