Gravity from the Sun and moon work together to give us tides here on Earth.
And in return, Earth’s gravity is cracking the moon’s surface.
Talk about a bad tradeoff.
Scientists have a pretty good idea of how the Moon formed.
The current theory is that about 4.5 billion years ago, a Mars-sized object, called Theia,
collided with the Earth, ejecting material into space.
This material then collected over what was left of Theia’s core, forming Earth’s
only natural satellite.
Unfortunately...we are slowly crushing it.
For most of us, the moon is a cold, unchanging structure pitted with craters from impacts.
However, current images of its surface prove that it is much more active than previously
thought.
Distributed throughout its entire surface are over 3,000 lobate scarps, which are thrust
faults indicative of compression.
There is a pattern in the orientation of these lobate scarps, suggesting that there is some
outside influence.
Hint: it’s us!
Well, the Earth more specifically.
Thrust faults form when one block of crust slides up another and are commonly found on
Earth in mountain ranges such as the Himalayas, but they're also found on Mercury!
Mercury's globally distributed fractures suggest the planet’s mantle has cooled, shrinking
its interior and distorting the crust.
Similar structures have been found on the moon, captured in images from NASA’s Lunar
Reconnaissance Orbiter.
To date, nearly three-fourths of the moon’s surface has been imaged, showing us smaller
versions of the scarps found on Mercury...but with one big difference.
Earth's gravity is affecting how these scarps are appearing on the moon's surface.
Without our gravity, the lobate scarps would be evenly distributed with random orientations,
but that’s not what we see!
Instead, near the equator and mid-latitude regions, most of the scarps were oriented
north-south, whereas at the poles they were mostly east-west.
Researchers say that these findings are consistent with the Earth’s gravitational tidal forces
affecting the moon’s surface.
Interestingly, the lobate scarps are geologically young.
They are estimated to be less than a billion years old with some of the youngest only a
hundred million years old.
Granted, to us, that age seems unfathomable.
But they are less than 25% the age of the moon.
In relation to the age of the Universe, that’s nothing.
The age estimation comes from the scarps appearing to cut across small craters.
Because the moon is constantly bombarded by meteors, the small craters are usually replaced
by larger ones relatively quickly.
So, if the lobate scarps are cutting through these young craters, they must have formed
later in time.
So then what is the fate of our moon?
Well, if the moon continues to cool and contract, it is likely to form new lobate scarps, likely
following the same pattern of orientations.
The shrinking size, roughly 100 meters over the last billion years, is unnoticeable to
us.
As the moon continues to get further from us every year, its decrease in angular size
will far outweigh its change in physical size.
Of course, in about 5 billion years when the Sun burns through the hydrogen in its core,
it will expand into a red giant.
And at that point, the moon’s compression will be the least of its worries.
Do you think we have a chance of surviving when that time comes?
Let us know in the comments.
Even though the moon is shrinking, it can look much larger when it is near the horizon.
To find out how this illusion works, check out this video over on my channel, Explorium.