Solar system questions look easy until a quiz asks which planet is hottest, which has the shortest day or which could float. NASA’s planetary fact pages answer all of these, and the real answers are often not what people expect. Here are seven facts, each taken from NASA’s own science pages, that regularly catch out quiz players.
The big picture: how many worlds?
NASA states that the solar system includes the Sun, eight planets, five officially named dwarf planets, hundreds of moons and thousands of asteroids and comets. It also says the whole system orbits the centre of the Milky Way galaxy and takes about 230 million years to complete one orbit. Quiz setters sometimes ask how many planets there are, and the current NASA answer is eight, with Pluto counted among the dwarf planets.
1. Venus: a day longer than its year
According to NASA, a Venus “day” lasts 243 Earth days, which is longer than a Venus year of 225 Earth days. Venus also spins backward compared with Earth, so the Sun would rise in the west and set in the east. NASA describes Venus as the hottest planet in the solar system, with surface temperatures hot enough to melt lead at about 467 degrees Celsius (872 degrees Fahrenheit), caused by a runaway greenhouse effect in its thick atmosphere.
2. Mercury: closest to the Sun, but not the hottest
A classic trick question. NASA’s Mercury page confirms that Mercury is the smallest planet and the one nearest the Sun, yet it is not the hottest. That title belongs to Venus because of its dense atmosphere. Mercury has no atmosphere to hold heat, so NASA gives daytime highs of about 430 degrees Celsius and night-time lows of about minus 180 degrees Celsius. It is also the fastest planet, orbiting the Sun every 88 Earth days.
3. Mars: home to the biggest volcano
NASA says Mars hosts the largest volcano in the solar system, Olympus Mons. It stands more than 25 miles (about 40 kilometres) tall from base to summit, far above Mount Everest at 8,848 metres, and its base covers an area as large as the US state of Arizona. NASA also notes that Mars is the only planet on which rovers have been sent to roam the surface. Its canyon system, Valles Marineris, is another record-holder: NASA says it extends about 2,400 miles (3,870 kilometres) and is more than 10 times longer and wider than Earth’s Grand Canyon.
4. Jupiter: biggest planet, shortest day
Jupiter is the largest planet: NASA says that if it were a hollow shell, 1,000 Earths could fit inside. It also has the shortest day in the solar system, spinning once on its axis in about 9.9 hours. NASA reports that the Great Red Spot, a swirling oval of clouds twice as wide as Earth, has been observed for more than 300 years.
5. Saturn: lighter than water
NASA calls it hard to imagine, but Saturn is the only planet in the solar system with an average density less than water. In NASA’s words, the giant gas planet could float in a bathtub if such a colossal thing existed. Saturn is also 9 times wider than Earth at its equator and takes about 29.4 Earth years to orbit the Sun.
6. Neptune: the planet nobody can see unaided
Neptune is the only planet not visible to the naked eye, according to NASA. It was discovered in 1846, and in 2011 it completed its first 165-year orbit since that discovery. NASA adds that sunlight on Earth is roughly 900 times as bright as sunlight on Neptune, so high noon there would seem like dim twilight.
7. Earth: still the only known home for life
NASA’s list of ten solar system facts ends with a reminder: so far, Earth is the only place in the solar system where life has been found. NASA says that more than 300 robotic spacecraft have left Earth’s orbit and that 24 US astronauts have travelled to the Moon.
Bonus: Uranus, the sideways planet
For a tie-breaker, NASA explains that Uranus rotates at a nearly 90-degree angle from the plane of its orbit. That tilt makes it appear to spin sideways, orbiting the Sun like a rolling ball. NASA also records that Uranus was the first planet found with the aid of a telescope, discovered in 1781 by the astronomer William Herschel, who at first thought it was either a comet or a star.
How to use these facts in a quiz
The best quiz answers come from understanding the reason behind each fact. Venus is hottest because of its atmosphere, not its distance. Jupiter is biggest yet spins fastest. Saturn is huge but made mostly of light gases. If a question seems to have an obvious answer, check whether it is one of these exceptions.
Ready to test the knowledge? The site offers three difficulty levels:
The bottom line
NASA’s planetary pages turn up surprises at every step: a Venus day longer than its year, a Mercury cooler than Venus, a Saturn that is less dense than water and a Neptune that cannot be seen without a telescope. Learn the reasons behind these facts, and solar system rounds become much easier to win.
Sources
- Our Solar System (science.nasa.gov)
- Venus Facts (science.nasa.gov)
- Mercury Facts (science.nasa.gov)
- Mars Facts (science.nasa.gov)
- Jupiter Facts (science.nasa.gov)
- Saturn Facts (science.nasa.gov)
- Neptune Facts (science.nasa.gov)
- Uranus Facts (science.nasa.gov)
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