Asteroids and Meteors

28 Jul 2019

At https://phys.org/news/2019-07-asteroid-earth.html ... Hat tip to William. An asteroid buzzed the earth and was barely noticed. It was 100m across and passed just 70,000 km away, last Thursday. The lack of warning shows how quickly potentially dangerous asteroids can cross the orbit of the earth. Astronomers have become adept at seeing asteroids at night - but not always so during daylight hours. The 2013 Chelyabinsk meteor was a case in point. It came from the direction of the sun (and was obscured by sunlight) - and nobody knew about it until it entered the atmosphere.

The story has now popped up at https://wattsupwiththat.com/2019/07/29/nasa-surprised-undetected-city-ki... ... which of course comes with lots of comments. NASA, it seems, were surprised by the asteroid as they were expecting a couple of other ones at a much further out trajectory. This one was a surprise and the headline says it was potentially a city killer asteroid.

At http://spaceweather.com (July 25th 2019) we are told a much smaller asteroid (or should that be a meteor) exploded over Canada after it breached earth's atmosphere a few days ago. It exploded and for a moment it was as bright as the moon, scattering pieces (meteorites) over the countryside of Ontario (see video of the fireball at the link). The so called asteroid was just 12 inches wide and disintegrated 16 miles above the surface. At https://phys.org/news/2019-07-fragments-fireball-ontario.html ... researchers are actively seeking fragments of the meteor - seeking the help of Joe Public in locating them.

At https://phys.org/news/2019-07-india-farmers-meteorite-rice-field.html ... a meteorite the size of a football plunged into a rice field in eastern India (in Bihar). Farmers working in the paddy field were startled when the lump of rock fell out of the sky, accompanied by a loud noise (as one might expect). It left a hole 4 feet deep and is said to have strong magnetic properties (suggesting a metal content unlike the chondrites that explode before hitting the ground). Apparently, peasants in India reported something similar a few months ago but NASA dismissed the idea. This one was sent to stick a finger up at NASA it would seem. Who is throwing them down from upstairs?

Meanwhile, Gary sent in a link to www.sciencealert.com/evidence-of-ancient-meteorite-impacts-have-been-fou... ... it seems that scientists researching the Tamiami Formation in Florida came across a lot of fossilised clams - and tiny silica rich glass spheres up to 5mm in size, even inside the clam shells. They are thought to have got into the clams as they keep their mouths open and filter the sea water passing across them. These clams were clammed shut and were prised open in a lab. They were forged in heat (no wonder the clams pulled the shutters down) and they can be created by volcanoes and even by industrial processes. In this case there is no volcanic rock in the vicinity of the Tamiami Formation and human activity is discounted as the formation is prior to the Holocene. It is said to possibly go back as far as the Pliocene or Pleistocne, somewhere between 5 million years ago and 12,000 years ago. The researchers have drawn the conclusion that the most likely explanation is that an impact event was responsible. Or perhaps an atmospheric explosion. Something capable of ejecting lots of debris into the air.

   ... The glass spherules are, in effect, mini tektites - but therein lies a problem as uniformitarian geochronology insists the formation was lain down in a number of layers - and the fossilised clams were found in four different locations. The implication, in the gradualist model, is that there were four impact events - which seems a trifle unlikely. No doubt if a nearby volcanic source had been found they could point a finger at multiple eruptions - as volcanoes tend to blow at irregular intervals. In this case that is not possible and as Gary says, the evidence appears to be that the sedimentary layer was laid down quickly and in one go. This is itself unsurprising as impact events would involve a lot of sediment production - and this even occurs with big volcanoes. The researchers are of course trapped in the uniformitarian straightjacket and are forced to think in terms of more than one impact - at the same spot on earth.