2019-09-08 21:00:00
As we know, last July 21 marked the fiftieth anniversary of the arrival of the first human being on the Moon. This has spurred old debates. One of these debates deals with whether the first traces left by the steps taken on the surface of the Moon are still there or not, and if they are, how long will it take for them to be erased.
As with all debates, we have two very polarized positions: 1. The traces are still there; 2. The traces have been erased.
Those who maintain that the footprints have been erased argue that at the moment of takeoff of the lunar module, the gases expelled by the engines would hit the ground and erase what was tens of meters around. Therefore, the first footprints, which were necessarily close to the descent ladder to the lunar surface, would have been erased.
Proponents that the footprints are still there argue that the Moon lacks an atmosphere and, therefore, the exhaust gases from the lunar module’s engine did not cause any wind that could erase anything. These gases would collide vertically with the surface of the Moon and bounce upward, without causing lateral air currents, as would happen in the Earth’s atmosphere. In addition, the lower part of the lander, the one with the support legs on the lunar surface, remained on the Moon, including the ladder, which should have protected the footprints from the minimal effects of takeoff.
For my part, I am inclined to think that the traces are still there. Many others also think so and argue, furthermore, that they will remain there without being erased for millions and millions of years. I am not that sure.
And I am not because an analysis of the data collected by the seismographs left on the Moon in the different Apollo missions clearly indicates that the Moon suffers from seismic movements. The reasons for these “moonquakes” are mainly two. The first is that the Moon is still cooling and, like any body that cools, contracts. Lunar contraction generates internal tensions, faults that slide over each other and seismic movements.
Another reason that stimulates seismic movements is that the Moon’s orbit is elliptical. This means that at some moments it is closer to the Earth (the perigee) and at other moments it is further away (the apogee). When it is closer, the Earth’s gravitational pull deforms the Moon more, making it more hollow in the direction of the Earth. When the Moon moves away, the warp reverses. This cyclical change in the lunar shape, although slight, favors the generation of moonquakes, which can be of considerable intensity, up to more than five degrees on the Richter scale.
The Lunar Reconnaissance Orbiter observation mission, which has been observing the Moon with a telescope in lunar orbit since June 2009, has detected that lunamotos manage to slide stones along the sides of craters, for example. It is possible that movements of smaller particles may also occur, including those of the famous lunar dust, the so-called regolith. These movements may finally alter the surface of the Moon and, with this, erase the traces of the first men who walked on it. We will have to wait a few thousand years to verify this, provided that first we are able to avoid erasing our own footprints on planet Earth.
Reference:
Shrinking Moon May Be Generating Moonquakes
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