There are eight official planets (sorry, Pluto) in our solar system: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and ...
If astrobiologists are ever going to detect life beyond our solar system ... gas giant planets today are the same kind of tools we will use to interpret the spectra of potential exo-Earths ...
Auroras are beautiful phenomena on Earth, but they aren't specific to this planet. In fact, they appear on many other planets ...