A few weeks ago, some 300 miles off the coast of New Zealand, scientists aboard the research vessel Tangaroa gently lowered two funky-looking orange orbs into the sea. Soon they disappeared, plunging of their own accord toward the depths of the Pacific Ocean.

They were prototypes, specialized robots designed to record temperature and other conditions all the way to the sea bottom, more than three miles down. Every few days since that June voyage, they have been surfacing, beaming their data to a satellite, then diving again.

With luck, a fleet of hundreds like them will be prowling the ocean in a few years, and the great veil of human ignorance will lift a bit further.

The startling reality is that in 2014, we know more about the surface of Mars than about the depths of the ocean. And that deficit is a huge problem as scientists try to understand how human activity is changing the planet.