How many space facts are there?

100, each with a named source and a link to it. Planets, stars, moons and the missions that studied them.

Where do these facts come from?

Mostly primary sources: NASA, the ESA, museums, universities and peer-reviewed papers. A fact is only published here once a source can be linked, and the wording is written fresh rather than copied.

Can I read them in one sitting?

The page lists the newest first and the search box narrows by word. Every fact links onward to a quiz, game or calculator on the same subject, so it works as a browse or as a jumping-off point.

Mondo Knows Facts

100 Space Facts, Each One Checked and Sourced

Planets, stars, moons and the missions that studied them.

100 facts on this shelf, each with a named source and a link onward to something to play or use on the same theme.

100 facts in Space

SpaceA day on Venus is longer than its yearVenus turns so slowly that its day outlasts its trip around the SunNASA Science SpaceVenus is the hottest planet in the solar systemThick greenhouse gases trap heat to make Venus hotter than MercuryNASA Science SpaceThe Moon is slowly drifting away from EarthLuni-solar tidal friction pushes the Moon outward by roughly four centimetres each yearNASA Science SpaceJupiter has the shortest day of any solar system planetThe gas giant completes a full rotation in under ten hoursNASA Science SpaceThe Sun holds nearly all the mass in the solar systemOver 99 percent of all matter in the solar system resides inside the SunNASA Science SpaceMars hosts the largest volcano in the solar systemOlympus Mons on Mars stands about two and a half times taller than Mount EverestESA SpaceSaturn rings consist almost entirely of water iceBillions of icy fragments range from microscopic specks to house-sized bouldersNASA Science SpaceA single teaspoon of a neutron star weighs billions of tonnesSuper-dense collapsed stellar cores pack enormous mass into tiny spheresESA SpaceThe Milky Way will collide with the Andromeda GalaxyIn four billion years our home galaxy will merge with its nearest large neighbourEncyclopaedia Britannica SpaceVoyager 1 is the farthest human object from EarthLaunched in 1977 the robotic probe is now travelling through interstellar spaceNASA Science SpaceMercury experiences extreme surface temperature swingsWithout a thick atmosphere Mercury swings from scorching days to freezing nightsNASA Science SpaceUranus rotates almost entirely on its sideAn axial tilt of 98 degrees causes extreme seasons lasting over 20 yearsESA SpaceNeptune features the fastest winds in the solar systemSupersonic storms on Neptune reach speeds over two thousand kilometres per hourNASA Science SpacePluto features a giant heart-shaped nitrogen glacierSputnik Planitia is a vast plain of frozen nitrogen ice on the dwarf planetNASA Science SpaceSaturn moon Titan has lakes and seas of liquid methaneTitan is the only world besides Earth known to host stable liquid on its surfaceESA SpaceEnceladus erupts giant geysers of water ice into spaceA global subsurface ocean vents through cracks near the south pole of Saturn moonNASA Science SpaceEuropa may hold twice as much water as all Earth oceans combinedA deep saltwater ocean sits concealed beneath the icy crust of Jupiter moonNASA Science SpaceGanymede is the largest moon in the solar systemJupiter giant satellite is larger than both Mercury and PlutoESA SpaceIo is the most volcanically active body in the solar systemTidal forces from Jupiter squeeze Io to drive hundreds of lava eruptionsNASA Science SpaceSunlight takes roughly eight minutes to reach EarthLight travels 150 million kilometres across space at 300,000 kilometres per secondNASA Science SpaceSpace is completely silent because sound needs a medium to travelWithout air or gas particles sound waves cannot propagate through the cosmic vacuumNASA Science SpaceA full NASA spacesuit costs millions of dollars to produceCustom life support systems turn every spacesuit into a tiny personal spacecraftNASA Science SpaceFootprints left on the Moon will last for millions of yearsWithout wind or water erosion Apollo astronaut tracks remain undisturbedSmithsonian Institution SpaceSaturn is the only solar system planet less dense than waterThe massive gas giant would float if placed in a vast oceanic basinNASA Science

All 100 Space facts

Test what you know

Turn these facts into a quiz: Space & Astronomy trivia questions, with an explanation after every answer.

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Questions people ask

How many space facts are there?: 100, each with a named source and a link to it. Planets, stars, moons and the missions that studied them.
Where do these facts come from?: Mostly primary sources: NASA, the ESA, museums, universities and peer-reviewed papers. A fact is only published here once a source can be linked, and the wording is written fresh rather than copied.
Can I read them in one sitting?: The page lists the newest first and the search box narrows by word. Every fact links onward to a quiz, game or calculator on the same subject, so it works as a browse or as a jumping-off point.