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Comment by KGIII | Hacker News Reader

I don't know if it remains true, because they had started an underwater mapping by drone project. But, until recently, or perhaps still, we had more accurate maps of the surface of the moon than we had maps of the bottom of the oceans.

There is a bunch of stuff we have left to do. There's still a constant stream of discoveries being made in the depths of the oceans.

The science is hardly settled and, I suppose, that's what makes it so exciting. We have critters we can't even fully understand how they survive, and then we have all sorts of smaller mysteries. Like eels... We only first observed them mating just a couple of years ago, and that was just a single species.

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There are approximately 3x10^28 molecules of water per cubic meter (assuming pure water, which is obviously not the case).

A third of the way to the moon, there are approximately 7x10^6 molecules of hydrogen per cubic meter[0].

From high earth orbit (assume 60k km), it's about 300k km to the moon.

The average depth of the ocean is about 3.5km.

For simplification, let's assume that a molecule of water and a molecule of hydrogen have the same density (which they don't)

From high earth orbit, in a straight line to the moon, there would be about 2x10^12 hydrogen molecules in the way.

From the ocean surface to the average depth, there would be about 1x10^32 water molecules in the way.

Not getting into the optical properties of water vs hydrogen, or the fact that the math is much different for a probe orbiting the moon, there's just more "stuff" between the ocean surface and the ocean floor, and a satellite and the moon.

[0] - http://www.physicsoftheuniverse.com/facts.html

I remember reading somewhere about some organization (not Google) hoping to map the entire ocean floor by sometime in the 2020s, but it is truly a gargantuan undertaking. As you say, we have far better mappings of the moon than we do of the ocean, and for good reason.

The data report [0] from the MH370 search offers good insight for how little we know of the ocean, and why it is so difficult to map in its entirety. Two points really stood out to me from their findings: 1) the current quality of our topographical maps and other images are low quality and mostly unhelpful for any sort of real research or analysis; 2) it took 3 years of dedicated masses of search teams from multiple countries just to produce quality maps of a tiny stretch of one part of one ocean.

To put numbers behind it, the MH370 report referenced above calculated their entire mapping efforts this way: "The search for MH370 collected 278,000 square kilometres of bathymetry data within the search area and 710,000 square kilometres of data in total, which includes the data acquired in transit between port and the search area. It is one of the largest marine surveys ever conducted." That's a lot of time (3 years), money ($160M, granted not all spent on mapping), and people, for a good chunk of sea floor. But the oceans comprise 360,000,000 square kilometers. Three years of dedicated, coordinated searching in the "largest marine survey" ever only mapped 0.2% of the ocean floor. So who knows what sort of motivation, incentives, time, and organizations it will take to get 100%.

[0] https://geoscience-au.maps.arcgis.com/apps/Cascade/index.htm...

> But, until recently, or perhaps still, we had more accurate maps of the surface of the moon than we had maps of the bottom of the oceans.

I believe this is still true. The search for the missing Malaysian airliner ended up producing way better maps of the seafloor in the search region than had ever been done before. That search region is a teeny tiny portion of the entire seafloor and it took years.

https://eos.org/project-updates/geological-insights-from-mal...

Meanwhile the entire moon has been mapped down to 328 feet resolution:

https://www.nasa.gov/multimedia/imagegallery/image_feature_2...

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