Asteroids...It is 100% certain we'll be hit.....

In April 2018 B612 foundation reported "It is 100 percent certain we'll be hit, but we're not 100 percent sure when”.
The UN declared the 30th June as International Asteroid Day to educate the public about asteroids.
According to NASA, asteroids are small, rocky objects, much smaller than planets. They orbit the Sun, like all the other planets in our solar system. The majority of these small, rocky objects thriving in our solar system are located, in the main asteroid belt, the region between mars and Jupiter.
These celestial bodies are the remains from the formation of our solar system. In that time when the solar system bean to form 4.6 billion years ago, the objects in the asteroid belt never had the chance to become a part of a planet.
All the asteroids are not the same type because asteroids formed in different locations at different distances from the sun.
Here are a few ways that they differ:
Asteroids aren’t all round like a ball, like the planets. They have jagged and irregular shapes. They could be hundreds of miles in diameter, but also could be as small as pebbles. Many asteroids are made of different kinds of rocks and material.
These pieces of rock can contain lot of valuable information about the history of planets and the Sun, because they formed at the same time as other objects in our solar system did.
There is an estimated 995 413 asteroids in our solar system. They range in size about 530 kilometres in diameter - to bodies that are less than 10 meters across. If we had to put together all the asteroids combined, the mass will less than that of Earth's own Moon.
Most of this ancient space rubble is irregularly shaped, though a few are nearly spherical, and they are often pitted or cratered. As they revolve around the sun in elliptical orbits, the asteroids also rotate, sometimes quite erratically, tumbling as they go. More than 150 asteroids are known to have a small companion moon. There are also binary asteroids, in which two rocky bodies of roughly equal size orbit each other, as well as triple asteroid systems.
There are three classes of asteroids based on what they are made of. The three classes are C, S and M types.
The C type asteroids or Chondrite asteroids are the common ones, forming around 75% of known asteroids. They are probably consist of clay and silicate rocks, and are dark in appearance.
The S type asteroids or stony or silicate asteroids are made up of silicate materials and nickel-iron.
The M type asteroids or metallic asteroids, they are moderately bright, but not all, it is made of nickel–iron, either pure or mixed with small amounts of stone.
Jupiter's massive gravity and close encounters with Mars or another object can change the asteroids' orbits, which means it can knock them out of the asteroid belt and make the go flying through space in all directions across the orbits of other planets. Stray asteroids and asteroid fragments slammed into Earth and the other planets in the past, playing a major role in altering the geological history of the planets and in the evolution of life on Earth.
Our scientists are continuously monitoring Earths-crossing asteroids, whose paths intersect Earth's orbit, and near-Earth asteroids that approach Earth's orbital distance to within about 45 million kilometres and may pose an impact danger.
The majority of known asteroids orbit within the asteroid belt, generally with not very elongated orbits. The belt is estimated to contain between 1.1 and 1.9 million asteroids larger than 1 kilometre in diameter, and millions of smaller ones.
Some asteroids share the same orbit with other planets and they are called Trojans asteroids, but do not collide with it because they gather around two special places in the orbit. There, the gravitational pull from the sun and the planet are balanced by a Trojan’s tendency to otherwise fly out of the orbit. Jupiter, Neptune and mars have Trojan asteroids. Don’t worry we also have them with our earth; yes NASA announced the discovery of an Earth Trojan in 2011.
Some objects have orbits that pass close by that of Earth and they know as Near-Earth Asteroids. Asteroids that actually cross Earth's orbital path are known as Earth-crossers. As of June 19, 2013, 10 003 near-Earth asteroids are known and the number over 1 kilometre in diameter is thought to be 861, with 1 409 classified as potentially hazardous asteroids - those that could pose a threat to Earth.
Asteroids become darker and redder with age due to space weathering. However evidence suggests most of the colour change occurs rapidly

Two robotic spacecraft are currently exploring asteroids up close: NASA's OSIRIS-REx is in orbit at asteroid Bennu and Japan's Hayabusa 2 is preparing to collect samples from asteroid Ryugu. Meanwhile, NASA's NEOWISE spacecraft, orbiting Earth, continues to improve on the most accurate survey of near-Earth objects every undertaken.
Courtesy : NASA