Armageddon Scenarios

What Would Happen if the Moon Got Hit by an Asteroid?

We constantly hear about the dire effects that we would face if Earth got hit by an asteroid but rarely is a major impact on the moon mentioned.

Chris Carrington

Published on

February 5, 2015

Image Credit: Sarah Stewart SETI Institute

We constantly hear about the dire effects that we would face if Earth got hit by an asteroid but rarely is a major impact on the moon mentioned. It’s happened before, many times in fact, so there’s no reason to think that it won’t, at some point, happen again.

So, what would the effects be on the Earth?

That, of course, depends entirely on the size of the impact and the damaged it caused to our only natural satellite.

An asteroid big enough to break the moon up but not totally destroy it would most likely see the larger fragments of the moon coming back together. The result wouldn’t be as pleasingly rounded as our current moon, but it would still exert a gravitational pull on the Earth so the tides wouldn’t suddenly cease and sunlight would still be reflected giving the night-time glow we are accustomed to. It’s the smaller fragments that would be the most problematic. They would likely form rings, like those around Saturn, and therein lies the problem. With alarming regularity, bits of moon would drop out of the ring and send meteorites towards Earth.

Taking it a step further, the moon gets totally destroyed by a rogue asteroid, then the problems really begin.

The tides would be affected, the oceans would be much calmer than they are at the moment because the moon’s gravitational pull exerts great force on the water here on Earth. There would still be some waves due to the pull exerted by the Sun, but they would be nowhere near the size of waves we see now.

The main issue with a lack of tides is that the oceans would not churn as well as they do now. Many species that rely on ocean currents to move to and from feeding grounds will die out. The circulation of nutrients would dramatically slow down affecting marine life and, therefore, the human food chain around the planet. Tens of millions of people rely on the oceans for their primary source of protein. Protein deficiency diseases such as Marasmus would increase.

I mentioned that the moon is pockmarked from the amounts of hits it has taken in the past. Many of those hits prevented the asteroids and meteorites from hitting Earth, and without the moon standing between us and the space rocks, impacts on Earth would be relatively more common on a geological timescale.

We have evidence showing what a meteorite that makes it to Earth can do. Meteor Crater near Winslow, Arizona shows what a lump of rock traveling at 26,000mph can do when it lands.

The Tunguska event in June 1908 flattened 770 square miles of forest, and that one was an air detonation. What if it had hit three hours earlier? Or eight hours later? Or any other time you care to choose. The rotation of the Earth plays a part in where these things land. Maybe London would have been wiped off the map, or Berlin…would WWI been averted had that been the case?

The moon acts as a brake of sorts on the ‘wobble’ the Earth undergoes as it moves through its 26,000-year cycle.Without the moon keeping the brakes on there is a distinct possibility that the Earth would wobble to a much greater degree and that the timing of the cycle would be altered. With NASA estimating the degree of tilt without a moon to be between zero…which would eliminate the seasons altogether, to 85° which would see the Earth on its side in relation to its orbit around the Sun…which would cause extremes of the seasons never seen before, the Earth would be a far less hospitable place to live. Africa would be periodically covered in ice and the North Pole would be hot and sunny. Migrating animals would head off as they always have and not find the breeding and feeding grounds that they expected. Again this would affect those who rely on wild game for food.

In short, the moon keeps everything down here on Earth relatively stable. We may moan about the winter storms and the droughts, but the alternatives are very much worse than anything we have experienced so far.

Just like we know that one day the Earth is going to get slammed by a large asteroid, then we know that this will also be the fate of the moon at some point. Although the moon taking a hit will lead to challenging conditions and most likely a large population reduction due to knock-on effects of food supply and climate extremes it is, I think, still preferable to the decades-long ‘nuclear winter’ we would most likely face if the same impact occurred on Earth.

Sources:

Resources:

SAS Survival Handbook, Revised Edition: For Any Climate, in Any Situation

The Prepper’s Blueprint: The Step-By-Step Guide To Help You Through Any Disaster