Of Earthquake, Moonquake, Spacequake and so on!

Did you ever wonder whether earthquakes only exist on Earth?

So here I was with a friend, chatting away about random things, and we suddenly asked ourselves: are there earthquakes on the Moon?

And here comes another fascinating and deep rabbity hole!

The short answer is yes, there are quakes beyond just Earth.

The long answer is yes, but not quite. There are Moonquakes, Marsquakes, Spacequakes, Sunquakes, Starquakes and on and on. Everything quakes!

What is an Earthquake?

I know, we all learned this at school, but a little refresher never hurt anybody.

Think of the earth as a multi-layered cake with a core (first solid then liquid), followed by a mantle, and finally at the top, a crust. When that crust gets upset, well, boom, it quakes.

An Earthquake can be caused by natural causes (tectonic plate composing the crust bumping into each other), result from volcanic activity or from man-made actions such as mining blasts or nuclear tests.

So, yes, those doomsday movies are not completely ludicrous.

A little side note, the location under the surface where the quake starts is called the hypocentre, when the direction directly above it, on the surface, is called the epicentre.

What is a Moonquake?

Moonquake is the shaking of the surface of the moon (I know, shocking revelation!).

These shakes are divided in 4 main categories, based on their origin:

Shallow Moonquakes, which occur at a maximum depth of 125 miles and are the result of a structural weakness in the interior of the moon, which is shrinking slowly over time thanks to the cooling of its central core;
Deep Moonquakes, originate between 500 and 750 miles under the surface and are caused by the elliptical orbit of the Earth, resulting in a compression and expansion of the body of the Moon; think about it, the Moon affects our tides, but this is a reciprocal relationship like any other;
Meteoric Moonquakes, caused by meteorite or other objects in space hitting the surface. I know the name is a bit of a give-away;
Thermal Moonquakes, result from the moon 30-day cycles of day and night with temperatures ranging from 130 degrees Celsius during the day to -173 degrees Celsius at night. To summarise, you alternate between oven slow cooking and popsicle. After a while it takes a toll!

Considering people have been talking about setting up a base on the Moon for decades, one could question the practicality of doing so in the middle of all those quakes. Just a naïve observation.

What is a Marsquake?

One could ask, how do we even know whether there are quakes on Mars? Well, we can thank the NASA who brought the first seismometer to the planet in 2018. Not to be too much of a nationalist but this particular piece of equipment was provided by the French space agency. Yes, for once the French are not mentioned for the mayhem they caused!

Now that being said, we know a lot about Moonquakes because there has been a seismometer there for over 50 years, it has been barely 5 years for Mars, which means scientific data is still in its infancy.

One interesting fact, it seems that Mars doesn’t have tectonic plates. One theory is that the quakes are caused by large section of rocks moving from hot regions within the planet heading upwards, toward the surface. Bottom line: we know it exists, but the dataset is still too small to allow for true interpretation and extrapolation. Ask again in 50 years!

What is a Spacequake?

I must admit I am struggling a little bit more to understand that one.

It is a tremblor in the Earth’s magnetic field, but it occurs in space. However, the effect can reach the surface of our planet in the form of electromagnetic reverberation which tends to scramble radio communications and GPS because of waves of ionization. Alright, I get it. But how exactly does the magnetic field tremble?

Well, and let me quote Wikipedia: “Spacequakes are caused when jets of plasma come into contact with the geomagnetic field some 30,000 km above Earth's equator. The impact sets off a rebounding process, in which the incoming plasma actually bounces up and down on the reverberating magnetic field until they dissipate in a process called repetitive flow rebuffing”.

I don’t want to be rude, but that doesn’t enlighten me one bit.

What on earth is plasma in that context? All I have in mind is plasma like in the hospital, liquid! I am not a space expert, but that doesn’t sound right. I don’t think liquid can just jump all the way to space. Can it?

It seems Earth plasmasphere is an inner part of the magnetosphere, just outside of the upper ionosphere, which are layers of the Earth atmosphere, located 65 to 90,000 kilometres from Earth. So, not a liquid then!

I love the explanation from the Royal Belgian Institute for Space Aeronomy, describing the Earth’s plasmasphere as “a doughnut-shaped region of low energy charged particles (cold plasma) centred around the planet's equator and rotating along with it. It forms a plasma cloud that enshrouds the Earth”. Doughnut shape? Ok, now I am tracking with you people!

So, you take this plasma with its little particles, it goes and hit the geomagnetic field head’s on and boom, you got a Spacequake and your radio goes wonky.

What is a Starquake?

Again, I am quoting Wikipedia: “A starquake is an astrophysical phenomenon that occurs when the crust of a neutron star undergoes a sudden adjustment, analogous to an earthquake on Earth”.

I don’t know about you, but I don’t see much neutron star in my life, so should we care?

Well, it seems that indeed, we should. There was a big Starquake recorded in 2004, which resulted in the release of gamma rays. Should this event had occurred within 10 light years of Earth, the quake would have triggered a mass extinction.

As a reminder, mass extinction is bad, so we should care, but there isn’t much we can do if such a thing were to happen in our backyard.

All of this to say, that Earth is not that special, and that everything quakes for a variety of reasons. Some are small, some are big, and some have the potential to be catastrophic for our health and survival.

I would like to say a little thank you to a very special friend, who never judges my rabitty-hole syndrome (RHS) and more often than not provide some ideas for articles! You will recognise yourself.

Sources: