Space science · 9+
Mercury is the smallest planet and the closest to the Sun. Its cratered surface resembles the Moon, and almost no atmosphere holds heat. One trip around the Sun takes only 88 Earth days, but its slow rotation makes one solar day last 176 Earth days.
NASA facts
Venus is close to Earth in size but has a very different environment. A thick carbon-dioxide atmosphere and clouds of sulfuric acid trap heat, making it the hottest planet. Venus rotates slowly in the opposite direction from most planets.
NASA facts
Earth is the only world known to support life. Liquid-water oceans cover most of its surface, and the atmosphere contains nitrogen, oxygen and protective layers. A moving crust recycles rock, while the Moon helps stabilise Earth's tilt and drives much of the ocean tide cycle.
NASA facts
Iron minerals give Mars its rusty colour. The planet has a thin carbon-dioxide atmosphere, enormous volcanoes, deep canyons and polar ice caps. Dry channels and minerals show that liquid water flowed long ago, so robots investigate whether ancient Mars could have supported microbes.
NASA facts
Jupiter is the largest planet and is made mostly of hydrogen and helium. Its colourful bands are fast-moving cloud systems, while the Great Red Spot is a giant storm observed for centuries. A powerful magnetic field surrounds the planet, and many moons form a miniature system around it.
NASA facts
Saturn's broad rings are made of countless pieces of water ice, from dust-sized grains to house-sized blocks. The planet itself is mostly hydrogen and helium and has no solid surface to stand on. Its low average density is less than water, although no ocean could hold a planet.
NASA facts
Uranus is a pale blue-green ice giant coloured by methane in its atmosphere. It rotates on its side, probably after a huge collision early in solar-system history, so its seasons are extreme. Faint rings and many moons orbit the planet's unusually tilted equator.
NASA facts
Neptune is the farthest major planet and takes about 165 Earth years to orbit the Sun. Methane helps colour its atmosphere blue, while enormous storms and the fastest measured planetary winds race through its clouds. Its large moon Triton orbits in the opposite direction to Neptune's rotation.
NASA facts
Pluto is a dwarf planet in the distant Kuiper Belt, not one of the eight major planets. New Horizons revealed mountains of water ice, craters, valleys and a bright heart-shaped region containing a vast nitrogen-ice plain. Pluto has a thin atmosphere and five known moons.
NASA facts
Ceres is the largest object in the asteroid belt and the only dwarf planet in the inner solar system. NASA's Dawn spacecraft found a cratered surface, abundant water ice below the crust and bright salt deposits in Occator Craterâevidence that salty liquid once moved underground.
NASA factsShort explanations, worked examples, hands-on practice, optional checks, and a note for grown-ups.
Begin with an overview of âMap the solar systemâ. Then learn the main idea, follow an example, and try it yourself.
8 minBegin with an overview of âFour rocky inner planetsâ. Then learn the main idea, follow an example, and try it yourself.
8 minBegin with an overview of âGas giants and ice giantsâ. Then learn the main idea, follow an example, and try it yourself.
8 minBegin with an overview of âDays, years, and tilted worldsâ. Then learn the main idea, follow an example, and try it yourself.
8 minBegin with an overview of âAtmospheres and extreme weatherâ. Then learn the main idea, follow an example, and try it yourself.
8 minBegin with an overview of âHow spacecraft build knowledgeâ. Then learn the main idea, follow an example, and try it yourself.
8 min