Space is a challenging place. We think of it as mostly empty, but that is not completely true. The vast sea of space in our solar system is filled with powerful radiation and bombarded with high-speed atomic particles. In addition, the Sun generates a continuous stream of particles that we call the "solar wind." The high energy radiation, the high energy particles, and the solar wind could prove dangerous to life here on Earth's surface. Earth's planetary shield -- the Earth's magnetic field working together with our atmosphere -- protects us.
Every magnet generates a magnetic field. Several objects in our solar system also have their own massive magnetic fields: the Sun, Earth, Mercury, Jupiter, Saturn, Uranus, and Neptune. The magnetic field around a planet that extends into space is called a magnetosphere. The magnetospheres of the planets interact with the particles from the Sun -- the solar wind. Within the magnetosphere, charged particles spiraling along the Earth's magnetic field toward the poles create beautiful aurorae, the northern and southern lights, when they interact with our atmosphere.
Magnetic fields can also create hazards. Magnetospheres trap high energy particles into radiation belts around planets. The distant gas giant planets do not need protection from the solar wind; instead, their powerful radiation belts create a serious hazard for spacecraft, as do our own Van Allen radiation belts here on Earth.
Earth's magnetosphere does more than shield us from the constant barrage of high-energy particles. It also protects our atmosphere and oceans from the solar wind, which would otherwise gradually erode them away into space. Mars' lack of a magnetosphere may be partly responsible for the thinness of its atmosphere and absent oceans. A magnetosphere on Venus could have prevented this planet's primordial water from escaping into space.
Given these critical roles, it is not surprising that several missions are actively investigating these planetary shields. The ongoing MESSENGER mission is mapping out Mercury's magnetic field, as is Cassini at Saturn, and Juno is on its way to do the same at Jupiter. The Solar Dynamics Observatory is also monitoring the Sun and its magnetic field to explore its impact on the near Earth space environment..
Explore this topic to investigate magnetic fields and planetary magnetospheres, through a variety of activities and mission resources. It's attractive stuff!