Did a meteorite kill a man in India?

Indian authorities inspect the site of a suspected meteorite landing on February 7, 2016 in an impact that killed a bus driver and injured three others on February 6 Image copyright AFP
Image caption The meteorite left a crater inside the campus of Bharathidasan Engineering College in Vellore

Did a meteorite kill a man in India last week?

As far as we know, an object fell from the sky into the campus of an engineering college in the southern city of Vellore in Tamil Nadu state on Saturday.

The explosion left a crater on the ground, blew out the window panes of nearby buildings, the windshields of parked buses, shattered a water tank and sent debris flying. The victim, a bus driver, was reportedly standing near the site of impact and was killed.

There appear to be no eyewitnesses to the moment of impact, but the college principal was among those who reached the spot first after hearing a loud blast.

"I was in my office at that time, and we felt a vibration in the building for nearly a minute. All the students and faculty members came outside and we saw a cloud of dust. Such was the intensity that a water tank exploded, killing the bus driver who had gone to drink water," G Baskar told The Hindu.

Tamil Nadu Chief Minister Jayalalithaa Jayaram said that the driver was killed by the falling meteorite. But scientists are sceptical, and one of the team investigating the incident has already said the rock is unlikely to be a meteorite.

Conflicting reports

Meteors are dust-sized particles that burn up as they plummet through Earth's atmosphere. Meteorites are larger, more durable objects that survive heating in the atmosphere and land on Earth.

There are conflicting reports about the rock.

Some talk about the police recovering a "small stone weighing about 10g, black in colour, irregular in shape that looked like lead". Others talk about a "hard, jagged object in dark blue and small enough to be held in a close hand".

Scientists have checked the crater, dug up the soil, and taken away the rock for examination.

Derek Sears, a meteorite and asteroid expert at Nasa's Space Science Division, has seen a photograph of the rock that fell in Vellore. "The image of the stone is too poor to tell anything, but I would have thought if the object killed someone we would have a large stone?" Good question.

Image copyright Tamil Nadu Police
Image caption Further tests were needed to confirm that the darkish rock was actually a meteorite
Image copyright Reuters
Image copyright EPA
Image caption A fragment of a meteorite which flew over Denmark earlier this month

Also, he says if the crater - or the "impact pit" - shown in the picture was produced by a meteorite "there may well be fragments that would kill a person if it hit them in the necessary way, say a direct blow to the head". No such fragments are reported to have been found.

Most importantly, says Dr Sears, scientists need to determine whether the rock is indeed a meteorite. Sometimes it is easy to determine by "just looking at the rock".

Distinctive texture

Most meteorites have very distinctive textures and a conspicuous thin black coating caused by atmospheric heating.

"You have to be a little cautious because meteorites vary so much in composition and texture, and a few even have a transparent coating," says Dr Sears.

"The coating (also called the fusion crust) has beautiful flow textures - it is actually a thin layer of melted glass that froze as the meteorite got into the thick atmosphere. Underneath the crust is a pale interior with crystals and spherules and, most conspicuously, tiny metal grains."

The best everyday test for a meteorite, says the expert, is to "touch it on a grinding wheel and look for shiny flecks of metal".

So India's scientists will possibly need to make a thin slice of the rock - "so thin you can see through it" - and look at the textures under a microscope. Then they would need to determine the major minerals and their compositions.

This would not only confirm that it is a meteorite, but identify the class and type. A final confirmation would be to analyse for elements and isotopes where you get more confirmation and more information on the rock and its history.

Image copyright AFP
Image caption Some scientists speculated that the rock could have come from a meteorite shower

Scientists say meteorite falls are fairly common, but the vast majority of them land in the sea or unpopulated regions. "To hit a town or a city is extraordinarily rare," says Dr Sears.

Mythology of fatalities

That is why a meteorite crashing in Russia's Chelyabinsk region - a fireball streaked through the morning sky, followed by loud bangs - was a major event. "It was a big fall and it hit a major city. Even then, no one was killed," says Dr Sears.

Scientists also have to contend with the mythology about human fatalities caused by falling meteorites.

Dr Sears is aware of "five or six people who were supposed to have been killed in China more than 1,000 years ago". Even that record is not certain. One unverified listing talks about one death - and that too in India - nearly 200 years ago.

Others like Ralph Harvey, professor of planetary sciences at Cleveland's Case Western Reserve University, say that many claims of "death by meteorite" throughout history have been always unsubstantiated.

He mentions "sensationalist accounts in the US designed to sell newspapers" - LOCAL MAN FOUND DEAD IN HIS BED WITH SMOKING HOLE THROUGH HIS CHEST, ran one headline - to very old accounts from China "where tax collectors would tell the emperor that whole villages had been destroyed by impact - a win-win for the villagers and the tax collectors if the story was believed".

"There are a few verified claims of getting bruised by meteorites, usually while sitting in one's house or car, and many examples of meteorites hitting or damaging property, particularly in the last 50-60 years," says Dr Harvey.

"In fact most meteorites in the modern era are found because they damaged something, whereas in earlier times when more people worked out in the fields, most meteorites were found because they were seen to fall from the sky or discovered by farmers."

So what could have fallen from the sky in Tamil Nadu last week?

Scientists like Dr Spears believe the most likely cause could be an object falling from an aircraft. Another, less likely cause, could be space junk - a piece of space junk, for example, entered the atmosphere just before Christmas, but it is doubtful anything made it to the ground. If it did, it possibly fell into the sea.

But one bit of information at the tail end of The Hindu report could contain some clues to Saturday's incident in India.

It says this was the "second such incident in 10 days" in the area. On 26 January, villagers "claimed that they saw a burning object fall from the sky on an agricultural field. The object left a three-foot-deep pit".

Maybe this is not a story about meteorites at all.

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