Beyond Mars lie the four gas giants: Jupiter, Saturn, Uranus, and Neptune. Jupiter is the Solar System's largest planet by far. Its moons include Io, which is volcanically active, and Europa, which may have an ocean of liquid water below its frozen surface.

Steppes and deserts make up almost a third of Earth's land surface and are an ideal place to practice geology due to the distinctive landforms, often unobstructed by vegetation. Explore alluvial fans, washes, playa lakes, dunes, and other features typical of arid regions. Also ask why steppes and deserts are so dry. What combination of surface, ocean, and atmospheric conditions produce them?

Jellyfish are, like the mythical Medusa, both beautiful and potentially dangerous. Found from pole to tropic, these mesmeric creatures form an important part of the sea's plankton and vary in size from the gigantic to the minute. Perceived as alien creatures and seen as best avoided, jellyfish nevertheless have the power to fascinate: with the sheer beauty of their translucent bells and long, trailing tentacles; with a mouth that doubles as an anus;...