In 2016, the United Nations declared June 30 Asteroid Day, which aims to educate people about asteroids, including the risks that are posed by asteroid impacts, how they were involved in the formation of the solar system, and more.
NASA keeps track of the asteroids we know of; right now there are at least 1,097,558 of them, many of which are found in the asteroid belt in between Mars and Jupiter, orbiting the Sun. Some are under 33 feet wide while others are as big as 329 miles in diameter.
It's thought that about 4.5 billion years ago, a dense cloud of dust and gas collapsed and formed a swirling disk called a solar nebula, which gave rise to the Milky Way. Material was pulled into the center and the Sun and eventually the planets of our solar system began to form as stuff clumped together. The leftover remnants became asteroids, meteors, or irregular moons.
Asteroids have orbits that can bring them very close to Earth, or in some cases, they collide.
June 30 marks the anniversary of the Tunguska Event, a massive explosion that occurred near the Podkamennaya Tunguska River in remote Siberia in 1908. Most scientists believe the blast was caused by an asteroid that weighed around 220 million pounds (or almost 100,000 metric tons) and was roughly 120 miles (193 kilometers) wide, which entered the atmosphere at an estimated 33,500 miles per hour (54,000 kilometers per hour). As it sped towards Earth's surface, it probably heated to 44,500ºF (24,704ºC).
The intensity of the heat and pressure caused the asteroid to annhilate itself, releasing an amount of energy that's equivalent to 185 Hiroshima bombs. The asteroid destroyed an area of about 800 square miles (2000 square kilometres). There is concern among some groups that we haven't done enough to detect inner Solar System Near-Earth Objects, which have the potential to cause mass destructon like the Tunguska Event.
Scientists, businesspeople, artists, and many others have banded together to call on the public to sign the 100X Declaration, which is a petition asking governments to promote and advance asteroid discovery research. Learn more here.
“The more we learn about asteroid impacts, the clearer it becomes that the human race has been living on borrowed time,” Brian May has said in a statement. “Asteroid Day and the 100X Declaration are ways for the public to contribute to bring about an awareness that we can get hit anytime. A city could be wiped out anytime because we just don’t know enough about what's out there.”