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The Sun and the Solar Wind: Earth has been spared the fate of Mars

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Stephen Marsh Stephen Marsh | 14:56 UK time, Monday, 10 January 2011

d ~ 25'728'000 km: day 10

Although space looks empty, it's not. It's full of lethal particles and radiation - and a lot of it comes from our Sun.

We know that the Sun warms our planet, provides the light by which we see and is vital for life on Earth but it also blasts out a barrage of deadly radiation.

In science fiction movies there are killer suns deep in space threatening to wipe out planets, and our Sun can be just as deadly. At the beginning of January a coronal hole opened up on the surface of the Sun and a stream of deadly radioactive particles blasted towards Earth.

Coronal Hole


Every day we are hit by a blizzard of radioactive particles. It's called the solar wind and it carries about one million tons of electrically-charged gas particles, away from the sun every second. It's made up of protons, neutrons, electrons, and alpha particles, the same materials the sun is made of and these particles travel through space at velocities of hundreds of kilometers per second. The barrage of solar wind is 24/7 but when a coronal hole opens up this allows a more intense solar wind to escape and shoot towards earth.

This wind can be deadly. Take a look at Mars. About a billion years ago it had an atmosphere. But over the millennia the solar wind has stripped the atmosphere from the planet's surface. Without its protective atmosphere, temperatures dropped and all the water was blasted off, leaving a cold barren planet.

Mars - Solar wind

NASA / Steve Bartlett

Fortunately our planet has been spared this fate, because we have a protective shield generated deep within the Earth. The core of the Earth is a ball of molten iron that spins, and it generates a magnetic shield that extends out into space. This shield deflects the solar wind around the planet. Some of the solar wind is deflected towards the weakest point of the shield, the poles. Here they react with oxygen and nitrogen in the atmosphere to create streams of different colours - a phenomenon known as the Auroras or northern and southern lights.

It's believed that Mars also had a molten iron core generating a protective shield. But because Mars is so much smaller than Earth its core cooled down and stopped spinning so the shield collapsed leaving the planet at the mercy of the solar wind.

Normally solar wind travels at around 400 km per second [250 miles a second] but the wind blasting out of a coronal hole shoots out at up to 800 kilometres a second [500 miles a second]. These solar wind particles will take around two to four days to reach earth but fortunately our magnetic shield is up to the task and deflects the potentially deadly particles away from the planet. The results of the cosmic battlefield should seen in the far north, is the shape of really dramatic northern lights.

If you are lucky enough to witness this celestial light show please email us your pictures or video.


  • Comment number 1.

    I truly think that when we look at mars we see the future of earth.. We´re bigger.. our core just takes more time to cool..

  • Comment number 2.

    Hi Marco,

    That's an interesting thought. When it comes to planets size does matter and perhaps we will eventualy share the same fate as Mars.


  • Comment number 3.

    Hi stephen, sure hope it takes a while to cool. Would be interesting to know when mars formed and cooled down. If we knew the mass too, then we should in theory be able to calculate how long the the earth will take to cool down..

  • Comment number 4.

    This comment was removed because the moderators found it broke the house rules. Explain.

  • Comment number 5.

    nasa has recently stated that there is 2 giant holes in the magnetosphere (the protective sheild you talk about) so therefore, how long before we all might die from radiation? is this why there have been dumbs (deep underground milatary bunkers been built all over the place in the states, and seed vaults etc? Please tell me the truth as time is running out im presuming and my little girl and i need to make plans for the time we have left. Im asking the question of very many others. millions in fact.


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