Our planet Earth faces potential catastrophic threats from within and without that could lead to irreparable damage and loss of life. While the threat from within is gradual, an outside threat would bring about immediate destruction. The outside threat would be from Near-Earth Objects (NEOs) like an asteroid or comet that passes close to the Earth’s orbit. On International Asteroid Day 2020, which is held on June 30 every year, we take a look at the dangers of an asteroid impact to our planet.Also Read - International Asteroid Day 2020: How And Why The Day Came to be Marked on June 30

According to NASA’s Center for NEO Studies, over 16,000 Near Earth Asteroids have been discovered, and there are many that have not been spotted as yet. The Earth has been hit by asteroids a number of times, but largest asteroid impact in recorded history is the Tunguska asteroid event in Siberia, Russian Federation on June 30, 1908.

The United Nations General Assembly, in December 2016, adopted resolution A/RES/71/90 and declared June 30 as International Asteroid Day. The day was held to mark the Tunguska asteroid event and to raise awareness among the public about the asteroid impact hazard. It was also marked to inform the public about the crisis communication actions to be taken at the global level in case of a credible near-Earth object threat.

The Tunguska event took over a sparsely populated area and it flattened an estimated 80 million trees over an area of 2,150 km (830 sq mi) of forest. It is classified as an impact event, even though no impact crater has been found. Eye witnesses of that time reported seeing a bright white bluish light, and what sounded like thunder or artillery fire. Those close to the impact said it felt like they were on fire, and the ground shook like there was an earthquake.

Early estimates of the energy of the Tunguska air burst ranged from 10–15 megatons of TNT to 30 megatons of TNT, which could easily topple over a huge building. The more energy is released during an impact, the greater the damage is likely to be on the ground due to the environmental effects of the impact.

There is also the danger of shock waves, heat radiation, the formation of craters with associated earthquakes, and tsunamis if water bodies are hit. People living within the affected zones are vulnerable to these effects, like in the Chelyabinsk meteor air-burst event over Russia in 2013. Although there is no record of a human being dying due to an impact, the Chelyabinsk event left over 1000 people injured.

Space agencies like NASA, the International Asteroid Warning Network (IAWN), and the Space Mission Planning Advisory Group (SMPAG) have been working towards identifying NEOs that pose a threat to Earth. The IAWN uses well-defined communication plans and protocols to assist Governments in case of such an event, and the SMPAG identifies technologies needed for near-Earth Object deflection.