59 Fun Facts About Asteroids

Most known asteroids orbit in the main belt between which two planets?

Mars and Jupiter bracket the belt, where Jupiter's gravity stopped the rubble from building into a planet and set it colliding into fragments.

Which astronomer proposed the word asteroid, from Greek for 'star-like'?

William Herschel chose it because, through the telescopes of the day, the new bodies showed no planetary disc, only star-like points that moved.

Which storybook hero lives on asteroid B-612?

The Little Prince's home got a real namesake: asteroid 46610 was named Bésixdouze because 46610 written in hexadecimal is B612.

Giuseppe Piazzi, who found the first asteroid, was an astronomer and also what?

A Catholic priest of the Theatine order, Piazzi first announced his discovery as a comet before its slow, even motion hinted at something more.

Piazzi's original two-part name for his discovery honoured a goddess and whom?

King Ferdinand III of Sicily was Piazzi's patron, and the goddess half of the name was Sicily's patron deity, so both parts honoured the island where he worked.

Meteor Crater, dug by an iron asteroid only about 50 metres wide some 50,000 years ago, is in which US state?

Arizona's Meteor Crater holds surprisingly little melted rock because the iron asteroid hit at only about 12 km per second, far slower than once assumed.

The asteroid belt's combined mass is roughly how much of the Moon's mass?

About 3%: astronomers weighed the whole belt by measuring how its gravity subtly tugs on the motions of Mars and the other planets.

Asteroids are broadly classified as C (carbonaceous), S (silicaceous) and which other class?

M (metallic) asteroids are nickel-iron, thought to be remnant cores of early bodies that partly melted and let their iron sink to the centre.

What makes an object a comet rather than an asteroid?

It shows a coma or tail when warmed because sunlight turns its ices to gas; comets that use up their ice go dormant and can look just like asteroids.

What is a small rock drifting in space, too small to count as an asteroid, called?

A meteoroid can be a chip of Mars knocked loose by an impact, which is how rocks from Mars have reached scientists here on Earth.

By 2026, astronomers had catalogued roughly how many asteroids?

About 1.5 million, a haul driven by automated sky surveys that can log thousands of new asteroids a month.

Which spacecraft was the first to fly through the asteroid belt, on its way to Jupiter?

Pioneer 10 crossed in 1972–73 and took fewer dust hits than feared, because the belt's asteroids are so spread out that craft pass through without incident.

Which asteroid is the brightest seen from Earth, at times faintly visible to the naked eye?

Vesta outshines larger asteroids because its light-coloured surface reflects unusually much sunlight, and it usually orbits closer to the Sun.

Which German astronomer, known for a paradox about why the night sky is dark, found the second and fourth asteroids?

Heinrich Olbers argued the first asteroids were shards of a destroyed planet, an idea later abandoned, and found the fourth while hunting for more pieces.

Which asteroid is the third-largest object in the asteroid belt by volume and mass?

Pallas lent its name to the metal palladium, which chemist William Hyde Wollaston isolated from platinum ore soon after the asteroid was found.

Which spacecraft, launched in 2007, orbited two different protoplanets of the asteroid belt in turn?

Dawn could orbit two different worlds because its hyper-efficient ion engines let it enter and leave orbit, which earlier chemical-rocket missions could not.

What did the famous bright spots in Ceres's Occator crater turn out to be?

Salt deposits: salty water from a deep reservoir below the crater percolated up and evaporated, leaving a highly reflective crust of mostly sodium carbonate.

Which spacecraft took the first close-up image of an asteroid, 951 Gaspra, in 1991?

Galileo's big dish antenna failed to open fully in 1991, so its later pictures, asteroids included, trickled home through far slower low-gain antennas.

Tracking the orbit of the tiny moon circling asteroid 243 Ida let scientists work out what about Ida?

How dense it is: the moon's orbit revealed Ida's mass, and the low density that followed all but ruled out Ida being made of iron-rich rock.

Which spacecraft made the first landing on an asteroid, touching down on Eros in 2001?

NEAR Shoemaker was never designed to land, yet it survived touching down on Eros in 2001 and kept sending data for about two weeks.

Which asteroid did Japan's Hayabusa probe sample on the first mission to bring asteroid material back to Earth?

Itokawa's dust reached Earth in 2010 after Hayabusa limped home on its ion engines, battling a fuel leak and failed reaction wheels.

Hayabusa2 returned samples of which asteroid to Earth in December 2020?

Ryugu's grains contained uracil, one of RNA's four bases, suggesting such building blocks formed in asteroids and reached the early Earth.

NASA's OSIRIS-REx collected a sample from which asteroid in October 2020?

Bennu's surface turned out so loosely packed that the spacecraft would have sunk into it had it not fired its thrusters right after grabbing its sample.

In which US state did the OSIRIS-REx sample capsule land in September 2023?

Utah's desert test range caught the capsule, but two stuck fasteners then kept NASA from fully opening the sample container for about three months.

NASA's DART spacecraft deliberately crashed into which asteroid moonlet in September 2022?

Dimorphos posed no threat; it was picked because it passes in front of its larger partner as seen from Earth, so telescopes could time any change in its orbit.

What gave NASA's DART crash far more push on its target than the spacecraft's own impact?

Debris blasted off the moonlet recoiled like rocket exhaust, which is why the moonlet's orbit around its partner shortened by more than half an hour.

What job did LICIACube, the small Italian spacecraft that rode along with DART, carry out?

Photographed the impact, a job DART could not do for itself, because the crash destroyed the spacecraft along with its own camera.

Which asteroid briefly had a 2.7% chance of hitting Earth on Friday 13 April 2029, per late 2004 estimates?

Apophis will instead pass about 32,000 km above Earth in 2029, closer than many satellites, and NASA redirected a spacecraft to study how the close pass changes it.

The name of the asteroid feared in 2004 is the Greek form of which Egyptian deity?

Apep, enemy of the sun-god Ra, suited a rock once feared as a doomsday threat, until radar tracking convinced NASA it poses no impact risk for at least a century.

As of 2025, the highest Torino impact rating ever given, a 4, falls in which colour zone?

Yellow, the zone 'meriting attention by astronomers': that 2004 rating lasted only four days before new observations ruled out an impact.

Besides the odds of a hit, what does the Torino impact hazard scale weigh?

The damage it would do counts as well, so even an object certain to hit rates 0 if it is too small to get through the atmosphere intact.

What does calling an asteroid 'potentially hazardous' mean?

It is large, with an orbit near Earth's, yet the label is no forecast: over 99% of known potentially hazardous objects pose no impact threat in the next 100 years.

The Chicxulub crater, from the impact that ended the dinosaurs, is buried under which peninsula?

Yucatán's buried crater rim shows up at the surface as an arc of sinkholes, because the impact left the overlying limestone prone to erode.

What made the Chicxulub impact so deadly worldwide, far beyond the blast zone?

Soot and dust dimming sunlight cooled the planet and stalled photosynthesis for years, collapsing food chains after the roughly 10 km asteroid struck.

Which rare element did the Alvarez team find concentrated at the Cretaceous–Paleogene boundary?

Iridium is rare in Earth's crust but more common in space rock, so a worldwide iridium-rich clay layer pointed to an impact, as the Alvarez team argued in 1980.

The geophysicists who found the Chicxulub crater in the late 1970s were prospecting for what?

Petroleum company PEMEX kept Penfield's survey data private, and he couldn't prove the buried ring was a crater until rock samples in 1990 pointed to an impact.

What injured most of the roughly 1,500 people hurt by the 2013 Chelyabinsk meteor?

Broken window glass: the shock wave arrived minutes after the dazzling flash and blew in windows across the region, so almost every injury was indirect.

Why did the Chelyabinsk object approach undetected?

Its direction was close to the Sun, a part of the sky asteroid-hunting telescopes can't scan, and the rock was only about 17 to 20 metres wide.

Why did the 1908 Tunguska event cause almost no human deaths?

It hit a remote, barely inhabited area: the blast flattened about 2,150 square km of forest, yet eyewitness accounts suggest at most three people died.

Asteroid Day is held every 30 June on the anniversary of which event?

The Tunguska explosion left no crater, because the incoming object burst apart several kilometres above the ground.

Why do Jupiter's trojan asteroids cluster ahead of and behind the planet?

The Sun's and Jupiter's pulls balance there, at two stable Lagrange points, so most trojans can stay trapped for billions of years.

The first Jupiter trojan, found by Max Wolf in 1906, was named after which Greek hero?

Achilles confirmed a prediction Joseph-Louis Lagrange made in 1772, that small bodies could be trapped sharing a planet's orbit 60 degrees ahead of or behind it.

NASA's Lucy mission to Jupiter's trojan asteroids is named after a famous what?

Hominin fossil Lucy lent the name because studying the trojans could reveal the 'fossil' materials that clumped together to form the planets.

Who spotted the asteroid belt gaps in 1866 and explained them by resonance with Jupiter?

Daniel Kirkwood showed that Jupiter's repeated tugs clear asteroids from orbits whose periods are simple fractions of Jupiter's, such as three circuits to its one.

Which asteroid, target of a NASA mission launched in 2023, was long thought to be a protoplanet's exposed iron core?

Psyche now appears to be part rock rather than a bare iron core: radar and heat measurements point to a mix of rock and iron-rich material.

Which asteroid is the fourth-largest object in the main asteroid belt?

Hygiea turned out to be almost perfectly round, so it may qualify as a dwarf planet, which would make it the smallest known one.

Which Chinese mission launched in May 2025 to sample the near-Earth asteroid Kamoʻoalewa?

Tianwen-2's target, Kamoʻoalewa, is likely a fragment blasted off the Moon by an ancient impact, so its sample could test that origin story.

Which company released the classic arcade game Asteroids in 1979?

Atari's Asteroids had a famous loophole: players left one or two rocks, lurked at the screen's edge and picked off saucers for points almost indefinitely.

Ceres fails which part of the IAU definition of a planet?

It does not dominate its orbit, which it shares with countless asteroids, and the same 2006 rule that made Ceres a dwarf planet also demoted Pluto.

During its 1900–01 close approach, astronomers worldwide tracked asteroid Eros to measure what?

The distance to the Sun came from measuring how Eros's position shifted when seen from observatories far apart, long before radar could do the job.

What process makes asteroids grow darker and redder as they age?

Space weathering by solar wind and micrometeorite impacts alters an asteroid's surface colour, so scientists must allow for it when reading its make-up from telescope spectra.

Which technique did Max Wolf pioneer in 1891 that dramatically sped up asteroid discovery?

Astrophotography let moving asteroids show up as short streaks among point-like stars on long exposures, and Wolf alone found 248 of them.

Which country hosts the Vera C. Rubin Observatory, which unveiled over 2,000 newly found asteroids in 2025?

Chile's Rubin Observatory sweeps the whole southern sky every few nights, so asteroids give themselves away by shifting position between visits.

The Titius–Bode law's prediction of a missing planet led astronomers to form which search group?

The Celestial Police split the planets' path across the sky into 24 zones, one per astronomer; Piazzi found the first asteroid on his own, and members found the next three.

Which famous December meteor shower comes from an asteroid, 3200 Phaethon, rather than a comet?

Geminids were thought to be fed by grains Phaethon sheds near the Sun, but its brightening there turned out to be glowing sodium gas instead.

The central peak of Rheasilvia, a giant crater on an asteroid, rivals which famous mountain in height?

Olympus Mons, the giant Martian volcano, is about as tall, and the collision that carved Rheasilvia likely blasted off a whole family of smaller asteroids.

What did astronomers detect coating the surface of asteroid 24 Themis in 2009?

Water ice, along with organic compounds, coats 24 Themis, backing the idea that asteroids carried ingredients that helped life on Earth get started.

MIT students' 1967 Project Icarus plan to destroy an incoming asteroid relied on which new rocket?

Saturn V rockets hadn't even flown when the students drew up their nuclear plan, and their report later inspired the 1979 disaster film Meteor.

Which space telescope's 2026 observations ruled out asteroid 2024 YR4 hitting the Moon in 2032?

James Webb caught the faint, distant asteroid in two narrow windows in February 2026, erasing a lingering 4% chance that it would strike the Moon.