Space has captured our imagination for long — from ancient Oriental and Greek astronomers as well as tribals of faraway regions to the current space giants — we humans have revered space as something to look out for, to cherish, as well as to fear. It is believed that life on the Earth started when an asteroid hit the Earth — it is not a coincidence that space features predominantly in our stories and myths.
But, space, alongwith being fascinating, is also hazardous for us humans. Fascinating because of the immense possibilities that it contains, and dangerous because of the objects that have the potential to wipe out entire species in a single go.
In this article, we will talk about the Potential Hazardous Asteroids, that have become a buzzword in recent times.
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Asteroids vs Meteors vs Comets
Before talking about the potentially dangerous asteroids, let us understand the difference between asteroids, comets and meteors first.
Asteroids lie in the asteroid belt, which is between Jupiter and Mars. These form the boundary between the Jovian Planets and the Terrestrial Planets. Asteroids are the largest of the three and thus deserve special attention. The current asteroid count in the asteroid belt is 796,916.
The size of an asteroid can range from 530km (329 miles) to less than 10 meters. One interesting point to note is that the combined mass of the asteroids is less than that of the Earth’s Moon.
These are classified into three classes based on the composition.
- C-type: Consisting of clay and silicate rocks.
- S-type: Consisting of silicate and iron-nickel.
- M-type: Consisting of metals which depends on their distance from the Sun.
Comets come from beyond Neptune and are made up of ice. Halley’s Comet is one of the well-known comets which appears after every 76 years. The currently known comet count is 3,588.
When comets come too close to the Sun, they began to glow up and emit a trail of light.
Meteorites are the objects of varying proportions in the space and are formed when the larger bodies break or blast. When these meteoroids enter the Earth’s atmosphere, they are called meteors (shooting star).
When the meteors fall on the Earth’s surface and survive, for them, we use the term meteorite.
Now that you have understood the difference let us come to the main topic.
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Potentially Hazardous Asteroids
Potentially Hazardous Asteroids are a subgroup of the Near-Earth Object (NEO) group. Near-Earth Objects denotes those comets and asteroids that are present in Earth’s vicinity, within a distance of less than 1.3 astronomical unit (au).
Note: 1 au = 149,597,870,700 m.
Potentially Hazardous Asteroids are those asteroids that have the potential to threaten Earth by making close approaches. There are several parameters by which the damage potential of asteroids, which are as follows.
- The asteroids which have the Earth Minimum Orbit Intersection Distance (MOID) of less than 0.05au.
- The asteroids that have an absolute magnitude of 22.0 or less.
Those asteroids which have the MOID of more than 0.05au and are smaller than 500 feet in diameter are not considered to be potentially hazardous.
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Techniques to save Earth from future collision
There are pieces of evidence to suggest that the Earth has been previously hit by the asteroids, the possibility of which we can not deny in future. According to NASA, for every 10,000 years interval, there is a chance that an asteroid might hit the Earth. The impact of such a collision can be extremely damaging and global in scale — acid rain, very high tides, firestorms and partial blocking of sunlight are some of the significant geographical changes of PHAs collision with Earth.
Thus, it is evident that we must put into place some mechanisms deflect the asteroid from its orbit. There are various ways to do so:
- Send spacecraft to the advancing asteroid and place such instruments that can deflect it.
- Detonating nuclear fusion weapons over the surface of an asteroid, which will cause it to deflect. It is worth noting that even a small deflection of few millimetres of the asteroid’s orbit over many years is enough for us.
- Use of large solar sails, which redirect a beam of sunlight towards the approaching object. The object might deflect from the pressure of the beam.
However, it is worth mentioning that blowing up an asteroid is not a good option, as blowing up the asteroid will cause the pieces to reach the Earth — handling which can be difficult.
In NASA’s admission, the threat to human life from Earthly happenings such as accidents, diseases or natural disasters is much more than that of an approaching PHA. However, the agency has cautioned that the threat cannot be dismissed altogether, and as such, we must continue to track the objects for future impacts.
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