This oft-repeated “fact” about the Moon and the ocean is totally wrong: ScienceAlert

This oft-repeated “fact” about the Moon and the ocean is totally wrong: ScienceAlert

This oft-repeated “fact” about the Moon and the ocean is totally wrong: ScienceAlert

“We know more about the Moon than about the depths of the sea.”

This idea has been repeated for decades by scientists and science communicators, including Sir David Attenborough in the 2001 documentary series The blue planet.

More recently, in Blue Planet II (2017) and other sources, the Moon is replaced by Mars.

As deep sea scientists, we investigated this supposed “fact” and found that it had no scientific basis. This is not true in a quantifiable way.

So where does this curious idea come from?

Mapping the depths

The first written record is found in a 1954 article in the Browsing Login which oceanographer and chemist George Deacon refers to a claim by geophysicist Edward Bullard.

A 1957 article published in the Journal of the Royal Society of Arts states: “The deep oceans cover more than two-thirds of the world’s surface, and yet more is known of the shape of the moon’s surface than here from the bottom of the ocean”.

This specifically refers to the sparse amount of data available on the topography of the seafloor and predates both the first crewed descent to the deepest part of the ocean, the Mariana Trench (1960), and the first moon landing (1969).

This quote also predates the practice of using ship-mounted echo sounders to map the seafloor from acoustic data, known as swath bathymetry.

Almost a quarter of the world’s seabed (23.4%, to be precise) has been mapped at high resolution. That’s about 120 million square kilometers, or about three times the total surface area of ​​the Moon. Perhaps that’s why the comparison has shifted to Mars, which has an area of ​​145 million square kilometers.

Map of Earth showing the Pacific Ocean and surrounding continents
Nearly a quarter of the planet’s seabed has been mapped in detail. (GEBCO)

A surprising number of visitors

Another related and incorrect comparison is that more people have set foot on the Moon than have visited the deepest place on Earth.

This assertion is difficult to substantiate. “The deepest place on Earth” could refer to the Mariana Trench, or simply the deepest part of it (the Challenger Deep, named after the British ship HMS Challenger).

Nevertheless, at least 27 and as many as 40 or more people have visited the Challenger Deep in early 2023. On the other hand, only 12 people have “set foot” on the Moon and 24 people have visited it.

Black and white image of old submarine hoisted above water
The bathyscaphe Trieste was the first manned vessel to reach Challenger Deep, in 1960. (US Navy)

Out of sight, out of mind

So why do people keep saying we know more about the Moon or Mars than we know about the deep sea?

It seems natural to compare the deep sea to space. Both are dark, scary and distant.

But we can see the Moon very easily just by looking up. By being able to see it, we more readily accept seemingly glowing rock hanging in the sky than very deep parts of the ocean. We can see the Moon wax and wane and we can feel the push and pull of the tides.

We feel like we know more about the Moon than we know about the depths of the sea, because we are forced to accept its presence. It impinges on our lives in tangible ways that the deep sea does not.

We don’t think much of the deep sea unless we watch a documentary or a horror movie, or maybe read about a “horrible alien monster” being dredged up by a deep-sea trawler.

A useful analogy

Because the deep sea is so physically inaccessible, comparing it to space can offer a useful analogy for an otherwise hard-to-imagine ecosystem. But some deep-sea scientists argue that the continued remoteness of the deep sea understates the vast amount of research on it that has emerged in recent decades.

Seabed biology is repeatedly referred to as a discipline that knows less about its own field of study than a relatively small barren rock devoid of atmosphere, water and life. And yet, this line of self-deprecation is repeated by scientists themselves, who may find that highlighting the knowledge gap about the deep seabed helps promote the need for ocean research.

Ultimately, the idea that we know more about the Moon than the deep sea is at best about 70 years outdated. We know a lot more about the deep sea – but there’s still more to know.The conversation

Prema Arasu, Postdoctoral Fellow, University of Western Australia; Alan Jamieson, Lecturer in Marine Ecology, University of Newcastle, and Thomas Linley, Research Associate, Marine Ecology, University of Newcastle

This article is republished from The Conversation under a Creative Commons license. Read the original article.

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