Perseid meteor shower on August 12, 2012.

The smallest and by far the most numerous ones have sizes of small dust particles and are called micrometeoroids they do not leave any visible trace behind when they enter the Earth's atmosphere. Anyhow, the vast majority of all meteoroids are just a few millimetres and less in size. Wikipedia states 10 metres other trustworthy sites call anything smaller than 1 km a meteoroid. There is no exact diameter that distinguishes an asteroid from a meteoroid. Other meteoroids are basically small asteroids.

Most of them originate from comets that lose gas and dust when they approach the Sun. Generally speaking, meteoroids are all the smaller objects in orbit around the Sun. Fortunately no people were killed during this event and today you can even buy a Chelyabinsk meteorite. Many of you will remember the Chelyabinsk event which took place on the 15th of February 2013. Anyhow, Sisyphus and none of the other big Apollo asteroids will collide with Earth in the next millennia which doesn't mean that smaller bodies can cause local damage. The largest Apollo asteroid - 1866 Sisyphus - has a diameter of about 9 km, similar to the asteroid that caused the Chicxulub event, the giant meteorite impact that caused the extinction of the dinosaurs. Apollo asteroids are doomed to sooner or later collide with one of the inner planets, usually within a few million years of their orbit becoming so eccentric. All asteroids with orbits so eccentric that they cross Earth's orbit are called 'Apollo asteroids', 'Amors' approach the Earth but do not cross Earth's orbit. The cause of these elliptical trajectories could be collisions within the asteroid belt or the gravitational influence of the massive planet Jupiter changing the orbits of some asteroids gradually over time (see orbital resonance). Some asteroids have very elliptical trajectories, crossing the orbits of the inner planets Mars, Earth or Venus. The scale of the solar system is so immense that even inside the asteroid belt the average distance between two asteroids is above one million km - or three times the distance between Earth and the Moon.Р”Р„steroid Itokawa, an Apollo asteroid with a length of 500 metres. If you try to envision the asteroid belt don't get fooled by some science fiction films: travelling around in the asteroid belt with your spacecraft doesn't require constant steering in order to avoid crashes with asteroids. The biggest body in the asteroid belt - Ceres - is officially not called an asteroid anymore but a dwarf planet. Even though there are millions of asteroids with sizes up to more than 500 km (like Pallas and Vesta) they are of no danger to the planet Earth. Most of them are in the asteroid belt between Mars and Jupiter. If a comet approaches the Sun it can generate a tail of gas and/or dust.Р”Р„n asteroid is a celestial body - composed of rock, metal or a mixture of both - that is orbiting the Sun. The part of a meteoroid or asteroid that survives the passage through our atmosphere and reaches the Earth's surface.Р”Р„ smaller celestial body mainly composed of ice and dust. Mostly debris of comets, sometimes debris of asteroids.Р”Р„ bright tail of light caused by a meteoroid during its atmospheric flight, also called a shooting star or falling star.Р”Р„ very bright meteor (brighter than the planet Venus).Р”Р„ fireball that explodes during its atmospheric flight, often with visible fragmentation.

Similar to an asteroid, but significantly smaller. What's the difference between asteroids, meteoroids, meteors, meteorites and comets?Р”В¬ontents Summary Table Asteroids Meteoroids and meteors Meteorites CometsР”Р„ celestial body bigger than 10 m orbiting the Sun, mainly between Mars and Jupiter

Asteroid vs meteoroid