Mercury is a planet with a tail. Here’s how that’s possible

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The planets of the Solar System look very much like a family. Jupiter is the father of treachery, keeping everyone responding. Uranus and Neptune are cool couples who just hang out with each other. Earth is the try-hard super-nerd. Pluto is the black sheep. And Mercury has a tail.

Yep. Almost like a giant olive comet, a tail streaming millions of kilometers away from the planet, shining with an orange-yellow light.

All this thanks to the position of the planet: Mercury is the innermost planet in our Solar System. It is less than half the distance from our star to Earth, an average distance of 58 million kilometers (36 million miles).

At that speed, the small, dense, rocky world is constantly battered in solar radiation and damaged by the solar wind.

Because Mercury has such a low mass – about 5.5 percent of the Earth ‘s mass – it is not particularly strong, with gravity. Its magnetic field is not particularly strong: only 1 percent of the Earth’s surface.

So the planet has nothing to call a rational feeling. Instead, a thin layer of oxygen, sodium, hydrogen, helium, and potassium atoms is mainly raised by solar wind and micrometeoroid explosion. That exosphere is firmly attached to the planet, but too loose to behave like a gas.

All this to say that the surface of Mercury has little protection against solar radiation and solar wind.

We know that solar radiation eliminates weight. We have even used that pressure to move a spaceship equipped with a sail, just as the wind directs ships. It is this radiation pressure that gives their tails comets.

As comets move close to the Sun, the ice inside them begins to sublimating, picking up dust as it escapes from the comet’s body. The pressure of solar radiation pushes that dust to a long tail, while the gas is shaped by the magnetic fields rooted in the solar wind; this is why comet tails are always flowing away from the Sun – not a movement that pulls out the tail, but so close to the star.

Mercury has ice, but the tail is not made that way. The main ingredient is sodium atoms; these shine when they are ionized by the sun’s ultraviolet radiation, in a process similar to what drives the Earth’s auroras.

As a result, the planet looks like a comet, with a tail that is seen flying nearly 3.5 million kilometers away from the planet.

In Venus, from time to time, when the solar wind blows in the right direction, there is a tail – like structure of ionized oxygen. Sodium can be in their tails. Jupiter Io moon is rich in sodium. And the Earth’s Moon has a sodium tail, bare and unprotected from the sun’s wind, though not as large or as light as Mercury.

But Mercury’s tail is special for another reason. By studying it at different times during the planet’s orbit, we can learn about the seasonal changes in Mercury’s exosphere, and how events such as solar flames and coronal mass ejections affect the planet. small.

Since sodium tails are mostly found in rock bodies, identifying sodium in systems around other stars may help us detect rocky exoplanets, and assess their viability.

It’s a great example of how planets can be very different from each other – every planet in the Solar System, even Uranus and Neptune, have their own norms. Each is a rare and valuable person; learn how and why there is a step towards understanding planets and outer planet systems in the larger Universe.

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