The earth’s oceans comprise 71 percent of the planet's surface. While humans have generally explored almost Earth’s entire continental surface, with the exception of Antarctica, there are substantial parts of the ocean that remain unexplored and understudied.
Even the latest technological advances for mapping the seafloor are limited by what they can do in the oceans. For example, in the southeastern Pacific Ocean an area as large as the state of Oklahoma has yet to be mapped. For the bulk of the ocean, scientists cannot distinguish seafloor topographic features because it is too deep to get reliable measurements. The accuracy and precision of most features on land that have been mapped are almost 500 times better than the resolution in the oceans.
For life at the microbial level in the oceans, many species, possibly thousands, remain unknown. There is very little known about the interactions between viruses and other marine microbes, making it difficult for scientists to identify and define new species once they are discovered. There is also much still to learn about large marine animals. For example, two new species of whales were discovered in 2003 and just this year scientists have proposed a new species of killer whale.
Even ocean temperatures can be difficult to measure. In fact, in only two parts of the world has the variation of ocean temperature over time been measured below depths of 1,000-2,000 meters (3,281-6,562 feet). Our understanding of the oceans is limited and enormous opportunities for discovery remain unfulfilled.
— John Orcutt, professor of geophysics, Institute of Geophysics and Planetary Physics