Earth’s gravitational forces are affecting its celestial satellite, by opening up cracks in the Moon’s surface, as scientists have noticed. Just as all lunar gravitational forces cause oceans and seas to increase and decrease their levels, as tides on our planet, the Earth influences the geological changes of the Moon. Studies have known this for some years, but now they have discovered that our much bigger planet opens up cracks on the surface of its satellite.
Everyone knows that the close connection between the Moon and Terra goes back billions of years ago, but for astronomers it was a shock to find that our planet is still shaping its space sibling.
The scientists examined information from the Lunar Reconnaissance Orbiter (LRO), one of NASA’s probes that was launched six years ago. The spacecraft assisted scientists in their discovery that the lunar surface is actually shrinking. Detailed LRO pictures have shown a series of lobe-shaped coves, which were likely created as the hot internal layers of the satellite cooled and became smaller, pushing the strong crust to crack.
After several years in space orbit and mapping almost 3/4 of all lunar areas, LRO has identified more than 3,000 of these unusual coves. These cracks are one of the more typical tectonic traits on the satellite’s surface, and are generally a few dozen feet in height and less than 5 miles in length. Past studies have indicated that they were around 40 millions years old, while are likely still transforming nowadays.
If the only influence on lunar cove development was the cooling of our Moon’s internal layers, the structure of these cracks should be rather random, since the causes of shrinkage would be equal in strength across all directions. Instead, they present a design in the orientation of a large number of coves, and it indicates that something else is affecting their development. This force also acts on a planetary scale and is represented by our planet’s gravitational forces.
Terra’s tidal effects do not behave similarly across all external areas of the celestial satellite. Instead, they mostly affect those lunar sides that are either the nearest or the farthest from our planet. The effect of these tidal forces is likely around 40 to 50 times less powerful than those caused by the moon’s shrinkage. A planetary model integrating the results of contraction and tidal forces on lunar surface matched in detail the coves seen on the satellite.
With LRO, US scientists have been able to see the Moon from close distance, a feature not yet possible with other probes in their space program beyond our planet. The recent LRO information set allows them to duplicate simple, but essential processes, which might otherwise have remained unnoticed.
If these lunar coves are still transforming, superficial “moon quakes” could happen along them. Such rumbles should occur most often while our planet’s tidal forces have the biggest effect on its satellite. A system of seismometers installed on all lunar surfaces may one day register these quakes.
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