These are the best space facts we have published, and every one of them links to the NASA page it was checked against. This is not a list gathered from other lists. Each claim below was compared with a sentence on a NASA page, and each card shows the source and the date the fact was verified. If a figure on NASA’s page is tied to a date, the claim keeps that date.
The facts are grouped by subject. Follow any title to read a short explanation, or follow the source link to read NASA’s own words.
Records among the planets
Start with a question most people get wrong. Which planet is the hottest? Mercury is the closest to the Sun, but it does not hold the record.
Venus Is the Hottest Planet in the Solar System
Venus is the hottest planet in our solar system, with a surface temperature of about 872 degrees Fahrenheit (467 degrees Celsius).
Mercury has a different record. It is the quickest around the Sun.
Mercury Is the Fastest Planet in the Solar System
Mercury is the fastest planet in our solar system, circling the Sun once every 88 Earth days.
Venus appears twice in this list, because it also spins so slowly that its day outlasts its year.
A Day on Venus Is Longer Than Its Year
Venus takes 243 Earth days to rotate once but only 225 Earth days to orbit the Sun, so a day on Venus is longer than its year.
At the other extreme is the largest planet, which turns faster than any other.
Jupiter Has the Shortest Day of Any Planet
Jupiter has the shortest day in the solar system, taking about 9.9 hours to spin once on its axis.
One planet lies on its side, and NASA gives the tilt to two decimal places.
Uranus Is Tilted Almost Completely on Its Side
Uranus is tilted 97.77 degrees, making it the only planet whose equator is nearly at a right angle to its orbit.
The giant planets
Jupiter’s most famous feature is a storm that people have been watching for centuries.
Jupiter's Great Red Spot Is Twice as Wide as Earth
Jupiter's Great Red Spot is a swirling oval of clouds twice as wide as Earth, and it has been observed for more than 300 years.
Saturn is the planet of large numbers and surprising small ones. It has more confirmed moons than any other planet, and NASA attaches a date to the count because new moons are still being confirmed.
Saturn Has 274 Confirmed Moons, More Than Any Other Planet
As of March 2025, Saturn had 274 confirmed moons, far more than any other planet in our solar system.
Its rings reach a long way out into space, yet from top to bottom they measure only a few feet.
Saturn's Rings Are Vast but Only About 30 Feet Thick
Saturn's ring system extends up to 175,000 miles (282,000 kilometers) from the planet, yet the main rings are typically only about 30 feet (10 meters) thick.
And for all its size, the planet itself is light for its volume.
Saturn Is Less Dense Than Water
Saturn is the only planet in our solar system with an average density lower than that of water.
The Sun, the Earth and the Moon
The Sun is so large that the comparison with Earth has to be made in millions.
About 1.3 Million Earths Could Fit Inside the Sun
It would take about 1.3 million Earths to fill the volume of the Sun.
Its light is fast, but not instant. What you see when you look at the Sun left it several minutes ago.
Sunlight Takes More Than Eight Minutes to Reach Earth
Light takes about 8.35 minutes to travel from the Sun to Earth, a distance of roughly 93 million miles.
The Moon keeps one face turned toward us, and NASA explains why.
The Moon Always Shows Earth the Same Face
The Moon rotates at the same rate that it revolves around Earth, so the same hemisphere faces Earth all the time.
It is also leaving, very slowly.
The Moon Drifts About an Inch Farther From Earth Every Year
The Moon is slowly moving away from Earth, getting about an inch farther away each year.
Earth itself has one distinction that has nothing to do with science and everything to do with language.
Earth Is the Only Planet Not Named for a Greek or Roman God
Earth is the only planet in the solar system whose English name does not come from Greek or Roman mythology; the name was taken from Old English and Germanic.
Mars and the small worlds
The Red Planet’s color has a plain explanation, and it is the same reason an old nail turns brown.
Mars Is Red Because Its Surface Is Rusty
Mars looks red because iron minerals in the Martian dirt oxidize, or rust.
Mars also has the largest volcano in the solar system. Our fact describes the area of its base and deliberately leaves out its height: the figure on the source page did not agree with figures given elsewhere, so we kept to what was not in doubt.
Olympus Mons Is the Largest Volcano in the Solar System
Mars is home to Olympus Mons, the largest volcano in the solar system, whose base covers an area about as large as the US state of Arizona.
The asteroid belt looks crowded in illustrations. Add all the asteroids together, though, and there is surprisingly little there.
All the Asteroids Together Weigh Less Than the Moon
The total mass of all the asteroids combined is less than that of Earth's Moon.
Pluto is small enough to compare with a country.
Pluto Is Only About Half as Wide as the United States
Pluto is only about 1,400 miles wide, about half the width of the United States and about two-thirds the diameter of Earth's Moon.
And one planet is too far away to see at all without help.
Neptune Is the Only Planet You Cannot See With the Naked Eye
Neptune is the only planet in our solar system that is not visible to the naked eye.
A space myth, corrected by NASA
One of the most repeated “space facts” is about something on the ground. NASA addressed it in the caption to a photograph taken from the International Space Station.
The Great Wall of China Is Not Visible From the Moon
The Great Wall of China is not visible from the Moon, and it is difficult or impossible to see from Earth orbit without high-powered lenses.
How these facts were checked
Every fact above went through the same steps. An editor opened the NASA page, found the sentence that supports the claim, and wrote the claim so that it says no more than that sentence does. The source, its tier and the date of the check are recorded with the fact and shown on its page, together with a confidence score out of 100.
Three habits explain most of the differences between this list and the space facts you may have read elsewhere.
First, we keep the source’s units. If NASA gives both Fahrenheit and Celsius, so do we. If it gives only one, we do not convert it ourselves, because that would add a number the source never checked.
Second, we keep dates. Counts of moons change as discoveries are confirmed, so a count without a date goes out of date without anyone noticing.
Third, we leave things out. When a figure could not be confirmed, or two pages disagreed, the fact was written around the part that was certain. A shorter fact that is right is better than a longer one that might not be.
NASA is a primary source for these subjects, since it runs many of the missions that made the measurements and publishes the results itself. We rank it Tier A, the highest of our four tiers. How we verify facts explains the tiers and the full process.
FactFusion AI uses AI assistance for content organization, explanation drafting, and classification. All facts are verified by human editors before publishing.
To meet these facts one at a time, try the random space fact generator, or browse the whole Space category.
Questions and answers
Are these space facts accurate?
Each one was compared with a NASA page by a person before it was published, and each links to that page so you can check it yourself. If you find an error, the fact’s page has a form for reporting it.
Why do you only use NASA for space facts?
NASA is a primary source for these measurements and publishes them openly. Other space agencies and peer-reviewed studies qualify in the same way and may be used for future facts.
Which is the hottest planet?
Venus. NASA gives its surface temperature as about 872 degrees Fahrenheit (467 degrees Celsius), hotter than Mercury.
How many moons does Saturn have?
NASA’s page says Saturn had 274 confirmed moons as of March 2025, more than any other planet. The number can rise as more moons are confirmed.
Can you see the Great Wall of China from space?
Not from the Moon. NASA says the wall is also difficult or impossible to see from Earth orbit without high-powered lenses.