1. Asteroids are relics from the time the solar system was born
Billions of years ago, when the solar system was forming, space dust and debris fused to form rocks and rubble. As the rocks churned, they rammed into one another, merged and formed planets and moons.
Asteroids are the leftover rubble from those times. They have remained unchanged over billions of years.
2. There are millions of asteroids in the solar system
Once Jupiter formed, its massive gravity held the remaining millions of space rocks captive and prevented them from forming more planetary bodies between Mars and itself. These rubble remnants in their pristine forms make up a rocky world — the Asteroid Belt— in the vast expanse between Mars and Jupiter.
These millions of asteroids are of varying sizes and circle the sun in wide elliptical orbits.
3. Some asteroids became the moons of planets
As asteroids orbit the sun, they sometimes cross paths, collide or ram into planets. Some of them get pulled into a planet’s gravity and become their moons. Some moons of Mars, Jupiter, Saturn, Uranus, and Neptune have origins this way.
4. Asteroids can have moons, rings and tails
Asteroids are just specks of space dust and rubble, are tiny in size and hence have a weak gravity. However, when a smaller rock comes in the periphery of a larger one, it gets pulled by the bigger one and becomes its moon.
In 2013, scientists observed that an asteroid could also have rings, which are nothing but a stream of dust particles circling the asteroid.
Also, sometimes two or more small asteroids fuse to form a tail-like extension to the asteroid.
5. They are odd-shaped masses
The rocky mass and weak gravity make asteroids irregularly shaped, varying between 2 m to 1000 m in size. Most of them are covered by a layer of dust. They cannot hold an atmosphere, and their average surface temperature is around -70 degrees Celsius.
6. Asteroids are rich in minerals and water
Asteroids are rich sources of carbon, silica and metals; Some have water-ice trapped in the rubble mass. Astronomers conjecture that when the asteroids frequently collided with planets in the early days, they delivered some of these vital elements to the planets. They believe life processes on earth could have kickstarted this way with carbon deposits.
Humans are exploring asteroids aggressively with an intent to mine asteroids’ mineral repositories. Some probes are on their way back to earth with asteroid rock samples for scrutiny.
7. Asteroids have water gullies
In 2015, scientists observed water trails called gullies on the asteroid Vesta. When a small asteroid collides with a bigger one, the impact melts the trapped water ice in the smaller asteroid, trickling on the bigger asteroid, leaving a water trail in the rocks.