But experts warn that extracting the minerals - used in technology ranging from mobile phones to electric vehicles - is both costly and difficult, especially when buried deep in the ocean.
A Japanese study published last week revealed an estimated 16 million tonnes of rare earths, with deposits to last hundreds of years.
The news made headlines internationally and in Japan, which is the world's second-largest consumer of these minerals but relies heavily on imports from China, which controls 90 percent of the highly strategic market. China extracted around 150,000 tons of rare earths in 2016, but has in the past restricted the supply amid political tensions.
For this reason, "Japan is looking for several ways of freeing itself from any dependence on Chinese supply," said Gaetan Lefebvre, an expert at the French Geological Survey.
In addition to wanting to cut reliance on China, the price of rare earths is rising due to a Chinese crackdown on illegal mining and a demand for electric vehicles.
The study's author, Yutaro Takaya from Tokyo's Waseda University, says his team hopes to develop ways to extract the prized elements within five years.