We learned about the countries and islands closest to the Mariana Trench, the deepest place on Earth. They are Japan, Guam and Indonesia. The Challenger Deep, in the southern end of the Mariana Trench (sometimes called the Marianas Trench), is the deepest spot in the ocean. Its depth is difficult to measure from the surface, but modern estimates vary by less than 1,000 feet (305 meters). There are some theories that there is sea life in the trench that may not be known. Also, can the Earth's core be reached through the Mariana Trench? There remains so much to learn about this part of our world!