Solar System — Answer Key
Part A: Fill in the Blank
Write the missing word or number on each line.
1. Mercury takes about 88 Earth days to complete one orbit around the Sun.
Mercury's short year (88 Earth days) is because it orbits close to the Sun and travels fast.
2. The largest volcano in the solar system, Olympus Mons, is found on Mars.
Olympus Mons on Mars is about 22 km high and 600 km wide — the tallest volcano known in the solar system.
3. Saturn is the least dense planet and could theoretically float on water.
Saturn's average density (0.69 g/cm³) is less than water (1.0 g/cm³), so theoretically it would float.
4. Venus rotates in the opposite direction from most planets, which is called retrograde rotation.
Retrograde rotation means spinning in the opposite direction. On Venus, the Sun rises in the west.
5. Jupiter's Great Red Spot is a massive storm that has raged for hundreds of years.
The Great Red Spot is an anticyclonic storm larger than Earth that has persisted for at least 350 years.
6. Neptune appears blue in color because methane in its atmosphere absorbs red light.
Methane absorbs red wavelengths and reflects blue light, giving Neptune (and Uranus) their blue-green color.
7. Uranus is tilted on its side at about 98 degrees, making its seasons extreme.
Uranus's 98° axial tilt means its poles experience 42 years of continuous sunlight followed by 42 years of darkness.
8. Earth's protective atmosphere shields living things from harmful radiation from the Sun.
Earth's atmosphere filters UV radiation and, combined with the magnetic field, protects life on the surface.
9. Mars has two small moons named Phobos and Deimos.
Phobos and Deimos are tiny moons of Mars, likely captured asteroids. Phobos orbits so fast it rises twice a day.
Part B: Matching
Match each item on the left to the correct answer on the right.
1. Match each item to its correct answer.
Mercury
→ Smallest planet with no atmosphere and extreme temperature swings
Hottest planet due to a thick carbon dioxide atmosphere
Venus
→ Hottest planet due to a thick carbon dioxide atmosphere
Has a famous ring system made of ice and rock particles
Jupiter
→ Largest planet with a storm called the Great Red Spot
Smallest planet with no atmosphere and extreme temperature swings
Saturn
→ Has a famous ring system made of ice and rock particles
Largest planet with a storm called the Great Red Spot
Mercury=smallest, no atmosphere, temperature swings(idx2); Venus=hottest, thick CO2 atmosphere(idx0); Jupiter=largest, Great Red Spot(idx3); Saturn=famous ring system(idx1)