Asteroid Impact, Its Effects and Deflection Mission
A near-earth object is the one that gets closer to Earth during its orbit. The near-earth object with a diameter of 150 meters or more would be designated a potentially hazardous object. Most near-earth objects are asteroids. A comet could also become a near Earth object on rare occasions. The effects of an impact caused by an asteroid or a comet could be catastrophic.
The near-earth asteroids larger than 150 meters in size are serious threats to our planet if they come closer than 4.6 million miles from Earth. An impact of a larger asteroid can cause serious damage to our planet. It is believed that a huge impact event that happened 65 million years ago was responsible for the extinction of dinosaurs.
There seems to be no serious threat to our planet from known asteroids in our lifetime. Small meteoroids bombard our Earth from time to time but these are not life-threatening events. There have been no human deaths in recorded history from an asteroid impact.
Extinction Level Events
If a large asteroid measuring 6 miles or more in diameter impacts Earth, there would be a serious threat to most life forms including human beings. The exact point of impact would cause a huge crater and there is little chance that any life form would survive in this region seconds after the impact.
The impact would be so severe that it would be equivalent to several million nuclear bombs exploding together. So it would be instant death for the life forms at the point of impact.
It would be a slow death for the people and living beings located elsewhere on Earth. The dust thus formed around our planet would block most of sunlight leading to an end of all plant life. The absence of plants would make most of the herbivorous animals extinct. Carnivorous animals would not have much to hunt either leading to mass extinction of most animal and plant forms.
Humanity would be the most affected as we are the least adaptable of all species to survive tough times.
If the point of impact is on ocean, it would cause gigantic tsunami waves triggering widespread devastation. If this is not enough, the Earth would be shaken by a huge Earthquake at an unprecedented scale.
Here is the good news. No known asteroid is on a collision course with Earth for the next one hundred years. So we can breathe easy.
Recent Impact Events
Asteroids, meteoroids or comets have been striking our planet Earth at regular intervals for a long time. Two minor asteroid impact events have happened in the last two centuries in Russia. Many such events could have happened in Southern hemisphere also but might have gone unnoticed because of less landmass.
Tunguska blast was the first such major impact event recorded in recent times. Tunguska is a remote forest region in the Northern part of Russia that is sparsely populated. On 1908, people were shocked to find that a huge tract of an uninhabited forest was flattened under mysterious circumstances. There was none living in that area to recount of what happened.
From the eyewitness account of the few who lived close-by, it is possible that an asteroid, or a comet had impacted the region. Since they could not find any crater, the entire asteroid must have disintegrated in the skies before reaching the ground.
Hundreds of miles of forest area was flattened during the Tunguska event. An earthquake measuring 5.0 on the Richter scale followed the impact. About 80 million trees were destroyed because of this explosion. There were no human casualties because the area remained uninhabited.
Russia had to bear the fury of celestial impact again on 15th February 2013. A smaller asteroid exploded in the atmosphere over the town of Chelyabinsk. The window panes in the buildings shook during the explosion resulting in breakage of glass. More than a thousand people were injured when the window glasses shattered following the explosion. For a brief while, the meteor shone brighter than the Sun before vanishing in the atmosphere.
We need to prepare ourselves for any future asteroid impact. Most space research organizations focus their effort on mapping the sky to look for any celestial body that could have a probability of impacting Earth in the foreseeable future.
Most small meteorites impacting the Earth do not hit the ground because the atmosphere acts as a protective layer shielding the planet from celestial threats. If the object is larger than few meters, part of it could survive and hit the Earth. An object larger than 150 meters in diameter can cause severe damage at a local level. If the object is larger than 6 miles in diameter, then the damage would be very severe at the global level.
Torino scale is used by the scientific community to show the level of threat from celestial impact events. Torino scale takes into account the probability of impact and the size of the object.
The Torino scale runs from 0 to 10. An asteroid or a comet is given 0 on Torino scale if it has no chance of an impact in the foreseeable future. An object is given a score of 10 if the object is sure enough to hit Earth and can cause widespread devastation.
Asteroid Impact Avoidance
The threat from an asteroid impact can be handled either through deflection or destruction. Deflection refers to causing minor shifts in orbits or velocity that would cause the asteroid not to cross the path with Earth. Deflection is an option when we have sufficient time in our hands, say a few years.
When an asteroid threatens to strike us with just a few months of warning, then deflection may be less effective as an option. We have to destroy the asteroid before it hits us with a nuclear weapon. We may not be yet ready for this option.
A comet is also a potential candidate to strike our planet with less notice. Comets possess an additional challenge because they travel many times faster than asteroids and their impact could be far more devastating. Destruction could be the only option against a threatening comet too.
Kinetic impact technique works on deflecting the asteroid by changing the speed of a threatening asteroid by a small fraction. We need to slam the asteroid with an object traveling at a huge speed. A small nudge would be sufficient to enough to alter its course. So we need sufficient preparation time for this technique to work well.
Spaceguard refers to the collective efforts of various space agencies to protect our planet from such impact events. So we can have a peaceful sleep in the confidence that there are many good souls working hard to protect us from threats we may not even think of.
- Mike Wall. (2014, June 18). Earth Impact: Are Comets a Bigger Danger Than Asteroids? [Blog post]. Retrieved from https://www.space.com/26264-asteroids-comets-earth-impact-risks.html
- Bruce Betts (2015, June 30). Five steps to prevent asteroid impacts [Blog post]. Retrieved from http://www.planetary.org/blogs/bruce-betts/2015/0630-5-steps-to-preventing-asteroid-impact.html
- Richard P Binzel. (2000, April 1). The Torino Impact Hazard Scale [Blog post). Retrieved from https://www.sciencedirect.com/science/article/pii/S003206330000006