#715 Do other planets have tectonic plates?

Do other planets have tectonic plates? In our Solar System, Earth is the only planet with tectonic plates, but in other solar systems there will probably be planets the same as ours.

Out of all the planets in the Solar System, Earth is the only one with tectonic plates. Neptune, Uranus, Saturn, and Jupiter are all gas giants and don’t have a solid surface to begin with. Mercury, Venus, and Mars are rocky planets, but they all have a solid mantle. The surface of Mars doesn’t move, which is why it has such giant volcanoes. Olympus Mons, the largest mountain in the Solar System, was constantly fed by lava from a hotspot beneath it. On Earth, the plate would move and the mountain would be severed from its source. That didn’t happen on Mars and Olympus Mons reached unimaginable heights. Mercury and Venus both have solid surfaces as well.

On Earth, we have tectonic plates but that wasn’t always the way. In the very early days, after the surface of the planet solidified, we probably had one crust, the same as Mars, Venus, and Mercury. It was only later that the crust broke up into plates. The plates move around and rise over other plates on one side and get pushed down by other plates on the other side. In this way, the mantle is constantly being refreshed as old mantle is pushed back into the Earth and new mantle is produced. The plates move around on a mush of semi liquid rock, and they are moved by convection currents.

So, why do we have tectonic plates on Earth, but other planets don’t? The gas giants obviously can’t have tectonic plates because they have no surface to have plates on. What is beneath their surface is anyone’s guess, but the pressure would be too great to have plates of any kind. Mercury cannot have tectonic plates because it has a very thick, solid outer surface. It may have a molten iron core, but the crust is too thick for it to move. Mars is in a similar position. Mars is much smaller than Earth and cooled down far more quickly. It probably also has a molten metal core, but a lot of the magma inside it has cooled down. The volcanoes on its surface are all dormant now. The crust is too thick and there is not enough magma for it to move around on. There is a canyon that runs for 4,000 km along the surface of Mars. Some people think that this might be the join between two tectonic plates, but they no longer appear to move.

Out of all the planets other than Earth, Venus is the most likely to have tectonic plates. It is about 90% the size of Earth and its makeup is very similar to ours. It is volcanically active and it has a large metal core. The core is made up of iron and nickel, just like Earth’s, and it is a similar size. Our core has a solid inner core and a liquid metal outer core. There is no way of knowing if Venus’s core is solid or liquid. In theory, because it is volcanically active and has a metal core, Venus could probably have tectonic plates. This idea was given more weight when the photos from the Magellan space probe to Venus in 1990 were further analyzed. There were ridges and grooves across the lowlands of the planet, almost like the pieces of a geometric jigsaw puzzle. Astronomers looked at them and thought that they could be geological signs that pieces of the mantle were pushing and pulling against each other. They have worked out that there are about 58 of these pieces and they crumple at the edges where they push against each other. However, they don’t seem to move like our tectonic plates do, and they don’t rise up or get crushed down into the planet like ours do, so they are not technically tectonic plates.

Some experts think that tectonic plates are necessary for life to evolve on a planet because they make it easier for gases to get out of the planet into the atmosphere. The gases are released through volcanoes and then pushed back into the planet when the plates are crushed under. This production and removal keeps the right amount of gas in the atmosphere. These gases, like carbon dioxide, are necessary for life to form. Recent research has shown that gases can pass through solid rock if there is enough heat and pressure, so plate tectonics aren’t necessarily necessary for life. One thing that is probably worth bearing in mind is that we have plate tectonics because the water inside the planet lubricates them and makes them move more easily. It may be likely that water is necessary for life and every planet with water also has plate tectonics. One of Jupiter’s moons, Europa, is covered in ice that seems to float on warmer water. These plates of ice move in exactly the same way that our tectonic plates move here on Earth. And this is what I learned today.

Photo by Pixabay: https://www.pexels.com/photo/planet-earth-220201/

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