We have been talking for years not about landing, but about colonize Mars (above all, Elon Musk), but with Artemis II making history and the Orion ship just splashed down After the first manned mission to the Moon in more than 50 years, the old moon has returned to the forefront. Four astronauts have just photograph it up close and leave us with our mouths open. But the Moon is much more than a satellite full of craters: each of those craters tells a story of billions of years.
At this moment when our satellite has hit us again, we rescue geological cartography most complete overview ever published. It is the unified geological map of the moonprepared in 2020 by the United States Geological Survey combining data from the lunar reconnaissance orbiter missions (LRO) from NASA and Kaguya from the Japanese Space Agency.
The good thing is that although you can see a general sample, you can also download it to have a greater level of detail, since it is at a scale of 1:5,000,000 and derived from six digitized geological maps. Visually, this world map draws attention both for the number of craters and for the shades chosen to color it. The choice of color is not casual or ornamental, but rather each color represents a type of terrain with a specific age and origin.
So, at a glance you know whether you’re looking at an ancient lava plain, a recent crater, or the original crust from 4 billion years ago. Without the colors, everything would be a gray mass of craters impossible to distinguish. The moon is full of secrets and this map provides information in abundance to discover them.
The unified geographic map of the moon
Fragment of the unified geological map of the Moon, scale 1:5M. Via: USGS
The moon has five geological eras: Pre-Nectarian, Nectaric, Imbrian, Eratosthenic and Copernican, which range from 4,000 million years ago to today. How to differentiate them on the map? Because they go from purple and orange for the oldest to green and pink for the youngest. All that is seen is the fossilized record of its turbulent youth because it has been “geologically dead” for almost 3,000 million years, but it had a turbulent past as evidenced by its orography.
The moon offers a striking visual dichotomy between the highlands (in reddish tones and saturated with craters) and the seas, which are the large dark spots. Of course, they don’t have any water. They are actually basaltic lava plains that filled huge impact basins about 3,000-4,000 million years ago. It is, in short, what we see from Earth. The clear, cratered areas constitute the original crust and are much older.
The most characteristic thing about the Moon to the naked eye are the craters, which are something like scars that witness the passage of time: the more softened, diffuse and even buried it appears on the map, the older it is. On the contrary, the sharper, brighter and surrounded by bright rays, the younger. “Lightning bolts” are bursts of dust and rock launched after impact and can extend for many kilometers. There is two especially spectacular craters on the map: Tycho and Copernicuswhose rays cross hundreds of kilometers and are geologically very recent.
The part of the Moon that we never see from Earth and that arouses so much curiosity in us (there is a project to install a radio telescope there) is its hidden side: there are almost no blue spots there. And while the visible side is rich in lava plains, the hidden side is a highland fortress, much more rugged and with a significantly thicker crust.
Map
At its south pole is the basin South Pole-Aitkenthe largest known impact scar in the entire Solar System, with 2,500 km in diameter and 8 km deep. Precisely that area where there are shadow craters science hopes to find water frost. This geological imbalance between both sides suggests that the Moon is asymmetric inside, a mystery that is also on the table of the scientific community.
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Cover | USGS, NASA
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