Only 19% of the ocean’s floor has been mapped in detail.
Source: Illustration by Kiyomi Morrison; Photo by Ishan/ Unsplash
Next Fact

Only 19% of the ocean’s floor has been mapped in detail.

Despite covering most of the Earth, much of the ocean has yet to be explored — or even mapped. A 2014 seafloor map developed by an international team of researchers revealed every oceanic feature larger than about three miles across, which means we have a strong sense of underwater mountains, but smaller objects — like centuries-old shipwrecks — continue to elude us. 

We know more about the surface of Mars than we do about the ocean floor.
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Incorrect.
It's a Fact
As hard as it may be to believe, we have indeed mapped the surface of Mars in more detail than we have mapped the ocean, despite the fact that no one has ever set foot on Mars. The entire Martian surface has been mapped at a resolution of at least 100 meters (328 feet).

The Nippon Foundation-GEBCO Seabed 2030 Project hopes to survey the entire ocean floor in detail within the next nine years. As of 2020, they estimated that 19% of the seafloor had been mapped in detail. (Precise resolutions vary with the depth of the ocean, but the project hopes to use a minimum grid of about 800 x 800 meters — or 2,625 x 2,625 feet — for the deepest portions.) They're working quickly: When the project began in 2017, only 6% of the seafloor was mapped in detail. Yet they still have an area roughly twice the size of Mars to cover.

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Numbers Don’t Lie
Depth (in feet) of the Mariana Trench, the deepest point on Earth
36,201
Percentage of the Earth’s surface covered by oceans
71
Length (in miles) of the mid-ocean ridge, a huge underwater mountain chain
40,390
Number of known marine species (although an estimated 91% of the ocean’s species await scientific description)
240,470
The world’s smallest ocean is the _______.
The world’s smallest ocean is the Arctic Ocean.
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Think Twice
The ocean isn’t blue because it reflects the color of the sky.

The ocean is blue because it acts as a kind of sunlight filter, absorbing colors from the red part of the light spectrum (long wavelength light) and leaving behind those in the blue spectrum (short wavelength light). What’s more, the ocean’s surface isn’t always blue — depending on what sediments and particles are floating in a given area, the light hitting them may result in a green or even reddish tint. There’s also the fact that most of the ocean has no color whatsoever: Very little light penetrates past a depth of 656 feet (the so-called “twilight” zone), and none at all makes it past 3,280 feet (the “midnight” zone).

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