Image: Earth’s magnetosphere. Credits: NASA's Scientific Visualization Studio/JPL NAIF
(NASA/Goddard) NASA Investigates Invisible Magnetic Bubbles in Outer Solar System
Space may seem empty, but it’s actually a dynamic place populated with near-invisible matter, and dominated by forces, in particular those created by magnetic fields. Magnetospheres — the magnetic fields around most planets — exist throughout our solar system. They deflect high-energy, charged particles called cosmic rays that are spewed out by the Sun or come from interstellar space. Along with atmospheres, they happen to protect the planets’ surfaces from this harmful radiation.
But not all magnetospheres are created equal: Venus and Mars do not have magnetospheres at all, while the other planets — and one moon — have ones that are surprisingly different.
NASA has launched a fleet of missions to study the planets in our solar system — many of which have sent back crucial information about magnetospheres. The twin Voyagers measured magnetic fields as they traveled out to the far reaches of the solar system, and discovered Uranus and Neptune’s magnetospheres. Other planetary missions including Galileo, Cassini and Juno, and a number of spacecraft that orbit Earth, provide observations to create a comprehensive understanding of how planets form magnetospheres, as well as how they continue to interact with the dynamic space environment around them.
Earth’s magnetosphere is created by the constantly moving molten metal inside Earth. This invisible “force field” around our planet has a general shape resembling an ice cream cone, with a rounded front and a long, trailing tail that faces away from the sun. The magnetosphere is shaped that way because of the near-constant flow of solar wind and magnetic field from the Sun-facing side.
Earth’s and other magnetospheres deflect charged particles away from the planet — but also trap energetic particles in radiation belts. Auroras are caused by particles that rain down into the atmosphere, usually not far from the magnetic poles.
It’s possible that Earth’s magnetosphere was essential for the development of conditions friendly to life, so learning about magnetospheres around other planets and moons is a big step toward determining if life could have evolved there.
