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