Oh, what it must have been like to live hundreds of years ago! Most of the world was a question mark. If you had an explorer's heart, the whole world must have seemed like one big frontier.

Christopher Columbus sailed to the New World. Pilgrims made their way to America. Once settled, the new Americans slowly made their way westward. Pioneers of all sorts made new discoveries every day.

The seas were sailed. New lands were discovered and mapped. Eventually, even the skies and outer space were explored.

But what about today? Is there any place left on Earth for the young explorers of today and tomorrow to explore? Where is the next frontier?

Believe it or not, there are still places on Earth that remain largely, if not totally, unexplored. For example, deep, dark, underground caves are some of the least explored places on Earth. While thousands of caves have been explored and documented, thousands and thousands more have yet to be discovered or explored.

Some areas on Earth are so barren and uninhabitable that they've been largely ignored. What lies beneath the 2-mile-thick ice sheets of Antarctica? No one knows for sure! Scientists would love to explore below the ice, though.

Recently, scientists have found evidence that hundreds of lakes lie below the thick ice, which could contain unknown forms of life. One of these lakes — Lake Vostok — is the sixth-largest lake in the world!

Other areas remain unexplored because they're extremely difficult to reach. The Mariana Trench, for example, is the deepest and darkest place in the oceans. New technology may one day make it possible for humans to dive deep enough to explore it. Such technology would open many doors, as only about 2% of the ocean's depths have been explored.

Scientists estimate there are about 140 million square miles of Earth that have yet to be explored. In addition to the ocean floors, these areas include mountaintops, steep valleys and canyons and remote areas, such as the mountains of New Guinea and the deepest jungles of Africa and the Amazon.

Of course, frontiers exist beyond Earth. In space, Mars could be the next frontier. Is a manned mission to Mars possible? Maybe in the future! Would you want to go to Mars one day? Why or why not? What about planets beyond Mars? Do you think it would ever be possible to explore another galaxy?

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