A new study claims that we know more about the surface of Mars than we do about our own oceans. Despite covering over 70% of Earth’s surface, the vast majority of the deep sea remains unexplored. In fact, scientists have now revealed that humans have directly observed less than 0.001% of the deep seafloor.
That astonishing figure comes from a new study published in Science Advances, which analyzed data from roughly 44,000 deep-sea dives conducted since 1958. To put that into perspective, our entire observed area of the deep sea is about the size of Rhode Island. Given the scale of the oceans, our knowledge of the deep sea is, at best, a starting point.
The deep sea begins roughly 200 meters below the surface, at the depth where sunlight disappears. It makes up more than 90% of the ocean’s volume, yet most of what lies beneath remains a mystery. The study also found that more than 65% of visual observations of the sea have come from waters near the U.S., Japan, and New Zealand, leaving huge swaths of the global ocean completely unstudied.
This matters because the deep sea plays a crucial role in stabilizing Earth’s climate. It absorbs about 90% of the excess heat and roughly 30% of the carbon dioxide produced by human activity. Without this buffer, global temperatures would be far more extreme. Yet despite its importance, our knowledge of the deep sea is too limited to fully understand how it’s changing—or how human actions might harm it.
That concern is growing as governments consider opening the deep sea to mining. An executive order signed by the Trump administration aims to fast-track approval for seabed mining operations to extract critical minerals. But with so little baseline data available, scientists warn we may cause irreversible damage to ocean ecosystems we haven’t even discovered yet.
Already, 32 countries have called for a moratorium on deep-sea mining until further research can be done. Experts argue that until we expand our knowledge of the deep sea, we risk blindly damaging one of the planet’s most important and least understood ecosystems.
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