Why does the Earth have a magnetic field, but Mars and Venus do not?

11 months ago

For a long time, the existence of a magnetic field in our planet seemed something completely natural – they say that a cat has four legs, a horse eats oats and hay, and the Earth has a magnetic field. So other planets have it too! In general, the existence of a magnetic field was not considered particularly important. Well yes, it’s convenient that the compass needle always points north. Nice such a trifle …

But in the second half of the 20th century, scientists began to understand: everything is not so simple! Already the first flights of satellites showed that the level of radiation in space simply “rolls over”. An ordinary window glass sent into space, after a couple of months becomes yellow, then brown and cracks!

“The solar wind” is constantly flowing from our Sun – a powerful stream of charged particles (electrons, protons and helium nuclei) flying at a frantic speed – almost 1000 kilometers per second. If this stream of radiation reached the surface of the Earth, life on it would never have arisen …

The solar wind carries another danger. If its energetic particles freely collide with the molecules of gases in the earth’s atmosphere, they (like billiard balls or bullets in a dash) split them and ruthlessly “throw” them into outer space. A powerful stream of solar radiation over several tens of thousands of years can “blow” all its atmosphere from the Earth!

However, a reliable shield rises in the path of the solar wind – the magnetic field of our planet. Charged particles are trapped in the field lines and fly by. Only a small fraction of ions nevertheless reaches our atmosphere in the regions of the North and South poles – and then we see such a natural phenomenon as the northern lights.

Scientists were even more surprised when our spacecraft reached the moon and other planets of the earth group – Mercury, Venus and Mars. It turned out that there is either no magnetic field at all, or it is incredibly weak, hundreds of times weaker than the earth! So, is our planet an exception?

No, distant gas giants – Jupiter or Saturn – have a magnetic field detected, and what a powerful one! But why is not the closest “relatives” of the Earth?

If we mentally “cut” the Earth in half, then deep down inside we find a solid red-hot (incidentally, hotter surface of the Sun!) Iron core. Between the solid core and the mantle is the outer core, in which iron is in a liquid state. It constantly “boils”, literally like water in a teapot – hotter particles rise up, cooled particles fall down (physicists call this phenomenon convection). And our planet is spinning fast, making 1 revolution around its axis in 24 hours! So it turns out a real planetary dynamo, in which electric currents are created of tremendous force. It is they who create the magnetic field.

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