It’s been 35 years since people last walked on the Moon. Astronauts Gene Cernan and Jack Schmitt wrapped up the Apollo program in December of 1972. In all, a dozen men left their footprints in the lunar soil -- and there are plans for new missions in about a decade.
It’s been a good bit longer since anyone saw the bottom of the deepest part of the ocean -- the Challenger Deep, in the Mariana Trench of the eastern Pacific. And there are no plans to send anyone back anytime soon.
In fact, the deep ocean is the least-explored part of our own planet. Thousands of people have climbed Mount Everest, and hundreds more reach its summit every year. Dozens of people work through the long, dark winter at the South Pole. Name almost any mountain, desert, jungle, or ice pack, and odds are that lots of people have been there.
Yet only two have been to the Challenger Deep. Jacques Piccard and Don Walsh reached the bottom -- a depth of almost seven miles -- in January of 1960, aboard the Trieste. Through a thick Plexiglas window, they saw a few fish and shrimp scooting above the featureless ocean floor.
Getting to the bottom of the ocean isn’t easy. Trieste had to withstand a pressure of eight tons per square inch, for example. And once you get there, there’s not much to see -- it’s completely dark; even with strong floodlights, you can’t see very far. So in many ways, the Challenger Deep is even more alien than the surface of the Moon.