How to use this quiz: choose an answer before opening the explanation. Each answer is supported by two independent sources checked on 2026-08-27.
10 space and astronomy questions
1 · Warm-up
On which planet is one orbit around the Sun shorter than one rotation on its axis?
- Venus
- Mercury
- Mars
- Neptune
Show the answer, explanation, and sources
Answer: Venus. On Venus, one orbit is shorter than one rotation.
Venus completes an orbit in about 225 Earth days, while one rotation takes about 243 Earth days. Its year is therefore shorter than its sidereal day.
Sources: NASA and Encyclopaedia Britannica.
2 · Warm-up
Why can Apollo astronauts' bootprints remain distinct on the Moon for millions of years?
- Moon dust melts into glass each night
- There is no wind or rain to erase them
- Magnetic rocks pin every grain in place
- Fresh dust seals each print from above
Show the answer, explanation, and sources
Answer: There is no wind or rain to erase them. The Moon has no wind or rain to erase the bootprints.
The Moon has no substantial atmosphere, so there is no wind or rain to smooth the tracks. Micrometeorites gradually disturb them over much longer periods.
Sources: NASA and Royal Museums Greenwich.
3 · Core
Which color appears closest to the Sun during a Martian sunset?
- Orange
- White
- Blue
- Green
Show the answer, explanation, and sources
Answer: Blue. A blue glow appears around the Sun during a Martian sunset.
Fine Martian dust scatters light differently from Earth's air, letting blue light stay concentrated near the setting Sun while the wider sky looks reddish.
Sources: NASA Space Place and Smithsonian National Air and Space Museum.
4 · Core
Which planet has an average density lower than that of water?
- Jupiter
- Neptune
- Uranus
- Saturn
Show the answer, explanation, and sources
Answer: Saturn. Saturn's average density is lower than water's.
Saturn's average density is about 0.69 grams per cubic centimeter, compared with about 1 for water. In a sufficiently large body of water, its average density would allow it to float.
Sources: NASA and Encyclopaedia Britannica.
5 · Core
The Sun's diameter is about 109 times Earth's. Approximately how many Earth volumes fit within the Sun's volume?
- 1.3 million
- 13,000
- 130 million
- 330,000
Show the answer, explanation, and sources
Answer: 1.3 million. The Sun's volume is approximately 1.3 million times Earth's.
The Sun's diameter is about 109 times Earth's. Because volume scales with the cube of diameter, the Sun has roughly 1.3 million times Earth's volume.
Sources: NASA and European Space Agency.
6 · Core
What did Apollo astronauts compare the odor of lunar dust inside the lunar module to?
- Wet concrete
- Spent gunpowder
- Burnt sugar
- Swimming-pool chlorine
Show the answer, explanation, and sources
Answer: Spent gunpowder. Moon dust reminded astronauts of spent gunpowder.
Astronauts could not smell lunar dust in a vacuum. After dust entered the module on their suits, several compared its odor with that of spent gunpowder.
Sources: Smithsonian Magazine and NASA Technical Reports Server.
7 · Core
Approximately how many times taller is Olympus Mons above the Martian plains than Everest is above sea level?
- About the same
- About twice
- About three times
- About ten times
Show the answer, explanation, and sources
Answer: About three times. Olympus Mons is approximately three times as tall as Mount Everest.
Olympus Mons rises about 25 kilometers above the surrounding Martian plains, nearly three times Everest's height above sea level. Its base also covers a much larger area.
Sources: NASA and European Space Agency.
8 · Core
After months in microgravity, how can an astronaut's height change?
- Shrink by up to 3%
- Stay exactly unchanged
- Grow taller by about 0.3%
- Grow taller by up to 3%
Show the answer, explanation, and sources
Answer: Grow taller by up to 3%. Astronauts can become up to 3% taller in microgravity.
Without gravity compressing the spine, the discs between vertebrae expand. The increase in height is temporary because gravity compresses the spine again after landing.
Sources: NASA and European Space Agency.
9 · Challenge
Because Uranus rotates almost on its side, how are its rings oriented relative to its orbital plane?
- Nearly vertical, like a rolling wheel
- Nearly flat, like Saturn's appear
- Randomly tilted in separate directions
- Trailing behind in a long spiral
Show the answer, explanation, and sources
Answer: Nearly vertical, like a rolling wheel. Uranus's rings are nearly vertical relative to its orbital plane.
Uranus's rotation axis is tilted about 98 degrees, so its equator and rings are nearly upright relative to the orbital plane. This orientation also produces extreme seasons.
Sources: NASA and Encyclopaedia Britannica.
10 · Challenge
How was Neptune's position first predicted before it was confirmed by telescope?
- Sailors tracked unusual ocean tides
- Mathematicians studied Uranus's orbit
- A photographer caught it by accident
- Astronomers detected its radio signals
Show the answer, explanation, and sources
Answer: Mathematicians studied Uranus's orbit. Mathematicians predicted Neptune's position from irregularities in Uranus's orbit.
Unexpected deviations in Uranus's orbit indicated the gravitational influence of another planet. Calculations directed telescopes to Neptune in 1846.
Sources: NASA and Royal Museums Greenwich.
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