What is a meteorite?
- A small natural object (smaller than a minor planet) is considered a meteoroid when it is outside the Earth’s atmosphere, a meteor when it is in the Earth’s atmosphere, and a meteorite if the object (or pieces of it) survives the entry through the atmosphere to land on Earth’s surface.
- A comet, on the other hand, is a chunk of ice and rock originating from the outer solar system, often accompanied by a tail.
- Meteorites are believed to originate in the asteroid belt between Mars and Jupiter. A meteorite may range in size from less than a gram to more than 60 tonnes. When the path of these space rocks intersects with the Earth’s orbit, the meteoroid enters the atmosphere at high velocity causing the luminous phenomenon called a meteor or -shooting star. These meteors, however, should not be confused with a meteor shower. Meteor showers involve the Earth passing through the orbit of a comet.
- A very bright meteor is called a ‘fireball’, and are referred to as a ‘bolide’ if associated with a smoke train and detonations, which often produces meteorites.
- Cases of injuries from these space objects are few and far between, barring the meteor sonic boom and shock wave at the Siberian city of Chelyabinsk on February 15, 2013, when 1,200 people were injured.
- According to the International Comet Quarterly, a non-profit scientific journal devoted to the observation, news and study of comets, the three most significant meteorite hits in India, before the Vellore incident, occurred at Mayurbhanj in Odisha on September 9, 2003; at Mhow in Madhya Pradesh way back on February 16, 1827 and at Oriang in 1825.
Who’s keeping track?
- While NASA’s Near Earth Object Program keeps a tab on larger space rocks in the Earth’s vicinity, it does admit that the job of keeping track of meteoroids is a more difficult task. According to NASA, every day, on average, more than 40 tonnes of meteoroids strike our planet. So why aren’t there more meteorites? NASA says most of the meteoroids are tiny specks of comet dust that disintegrate harmlessly high up in Earth’s atmosphere, producing a slow drizzle of meteors in the night sky. Bigger chunks of asteroid and comet debris yield dozens of nightly fireballs around the globe. Only some are large enough to pepper the ground with actual meteorites.
- Among the most comprehensive meteor watchers is The International Comet Quarterly (ICQ) , which keeps track of these space projectiles. The ICQ was published at the Smithsonian Astrophysical Observatory in Cambridge, Massachusetts, full-time from 1990 until early 2010 (part-time during 1980-1990). Beginning in 2010, it is being published at the Earth and Planetary Sciences Department at Harvard University.
What are the odds?
- According to earth sciences professor Stephen A Nelson, who in 2014 published a paper on the subject, the lifetime odds of dying from a local meteorite, asteroid, or comet impact is 1 in 1,600,000. In comparison, the paper suggests, the odds are 1 in 90 for a car accident, 1 in 250 for a fire, 1 in 60,000 for a tornado, 1 in 135,000 for lightning, 1 in 8 million for a shark attack, and 1 in 195 million for winning the lottery.
- According to data compiled by The Economist, the odds that an asteroid impact will destroy you in a given year are 1 in 74,817,414. For comparison, the magazine adds, the odds of dying from a bee or wasp sting are 1 in 25,364,571; by lightning, 1 in 10,495,684; from falling down stairs, 1 in 157,300. While the data does not correspond to India, it does, however, depict that chances of dying this way are very slim.
- NASA has an iPhone app called ‘The Meteor Counter’ that helps amateurs track meteoroids. Every time you see a meteor, you simply need to tap a key corresponding to its brightness on the app.
- The app records data such as the time you saw the meteor, the meteor’s magnitude, your location etc. The data is then automatically uploaded to NASA researchers for analysis.
Ctsy: Indian Express