Going Off the (Really) Deep End

DIVING INTO THE DEEPEST PLACE ON EARTH, CHALLENGER DEEP IN THE MARIANA TRENCH

- Carrie Clickard

Help Wanted: Expedition seeks explorers brave enough to face bizarre, glow-in-the-dark creatures. Must be able to navigate safely past vents spewing liquid carbon dioxide, erupting mud volcanoes, and a treacherous lake of molten sulfur.

What strange corner of the universe is this expedition headed for? It's a cozy little planet known as Earth and a spot miles under the surface of the Pacific Ocean called the Mariana Trench.

A Hole in the Ocean Floor

In 1872, the HMS Challenger expedition set out to map the ocean floor. The explorers spent four years crisscrossing the globe, sailing 70,000 miles (112,654 kilometers)-one-third of the distance to the Moon. It was backbreaking, boring work. Sail about 200 miles (322 kilometers), drop a weighted rope into the water. Measure how much rope it took to hit bottom. Sail another 200 miles and do it again. And again. This expedition was a total snooze fest, until a day in 1875 about 200 miles (322 kilometers) off the coast of Guam. That morning, when the to pe was dropped, the ocean swallowed up five miles (eight kilometers) of it. The Challenger's crew had discovered a "hole" in the ocean floor.

Braving the Depths

It wasn't until the 1950s that we knew just how big Challenger's discovery was. Scientists turned to sonar, an instrument that sends out sound waves and measures how long it takes them to come back. They discovered that the hole is actually a trench. It is crescent-shaped and twice as long as the state of California and 43 miles (69 kilometers) wide. Parts of the trench are only five miles (eight kilometers) deep, but at its southern end, the trench drops to almost seven miles (11 kilometers). That means if you planted Mount Everest on the bottom and stacked three Empire State buildings on top, you still wouldn't reach the surface of the ocean.