Over 70 percent of our planet is covered by ocean, but humanity has explored less than 5 percent of these waters. Even as we prepare to probe oceans on other worlds, our own remains largely mysterious. That's the drive behind the latest XPRIZE challenge, which offers $7 million in prizes to the teams that build the best ocean-exploring robots.

XPRIZE, which is known for hosting challenges meant to get new blood into space exploration, sponsors several contests related to ocean health and clean-up. But this is the first one focused on deep sea exploration.

Teams around the world have nine months to sign up for the challenge, and another year after that to develop their robots for the first round of the competition. All together, the competition is expected to last three years, with two rounds of judging: Round 1 will feature the top 25 teams (as determined by submitted technical criteria) operating their robots at an ocean depth of 2,000 meters, or about 1.2 miles. In round 2, up to 10 finalists will put their robots to the test at 4,000 meters, which is nearly 2.5 miles below the surface.

4,000 meters below is the boundary of what we call the Abyssal zone, which totally isn't creepy. After just 1,000 meters, no sunlight penetrates the ocean. Temperatures hover just a few degrees above freezing, and at 4,000 meters the ocean exerts around 400 atmospheres of pressure -- over 5,800 pounds per square inch.

That's hostile territory for a manmade robot (though not for many weird, mysterious living creatures), and it's going to be tough to earn the big bucks. $4 million will go to the team that operates the best robot, producing the best maps and images. The team with the second-best score will get $1 million, and another $1 million will be distributed evenly among the top ten teams from the first round. There's also a voluntary bonus prize of $1 million, sponsored by the National Oceanographic and Atmospheric Administration, that will reward the first team to develop new biological and chemical sensor technology.

With any luck, the prize will inspire some exciting new tech that makes our own planet just a little less mysterious.

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