Astronomy / Space Asteroid stike rate 'increase threefold over last 300m years'

Para Handy

Para Handy
From The Guardian:

https://www.theguardian.com/science/2019/jan/17/asteroid-strikes-earth-moon-threefold-dinosaurs

Asteroid strikes 'increase threefold over last 300m years'

Planet and moon have been hit by more asteroids in the past 290m years than at any time in previous billion

The rate at which asteroids are slamming into Earth has nearly tripled since the dinosaurs first roamed, according to a survey of the scars left behind.

Researchers worked out the rate of asteroid strikes on the moon and the Earth and found that in the past 290m years the number of collisions had increased dramatically.

Before that time, the planet suffered an asteroid strike about once every 3m years, but since then the rate has risen to once nearly every 1m years. The figures are based on collisions that left craters at least 10km (6.2 miles) wide.


The study's paper:

http://science.sciencemag.org/content/363/6424/253

Earth and Moon impact flux increased at the end of the Paleozoic



The Guardian's article also links a really neat yootoob video:

[video=youtube;ANYxkwvb8pc]https://www.youtube.com/watch?v=ANYxkwvb8pc[/video]
 
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Para Handy

Para Handy
Arry said:
I was going to ask; how can this be proved or disproved? But after watching that; I don't care.
Click to expand...

You made me realise I had forgotten to link the article from The Guardian - done it now. :eek:

As I think they are saying - the study theorises / postulates that by studying the rate of heat loss of ejecta around craters they can estimate when the impact was. The nub of their position is that the rocks that are the ejecta gradually get worn down in time due to micro-meteorite bombardment, the larger a rock is the longer it retains it's heat, hence the more recent the impact.

'Using images from Nasa’s Lunar Reconnaissance Orbiter, the scientists studied the “rockiness” of the debris surrounding craters on the moon. Rocks thrown up by asteroid impacts are steadily ground down by the constant rain of micrometeorites that pours down on the moon. This means the state of the rocks around a crater can be used to date it.

“When you have a fresh impact you get a lot of large rocks that sit around the crater, but over time they get bombarded by small micrometeorites and are transformed into lunar regolith,” said Sara Mazrouei, the first author of the paper and a planetary scientist at Toronto.'

from elsewhere:

'The craters were dated by studying how fast the ejected material cools during the lunar nighttime. The debris from older craters has crumbled more over time and the smaller pieces are able to cool very fast. Younger craters are still surrounded by ejected boulders which stay warmer for longer. '


BTW - (I posted this elsewhere) - the sound behind the impact effects is a conversion of the Moon's elevation into sound waves:

(Maybe the Canonn Research Group audio analysis section can find an alien message in it. :) )


[video=youtube;C0XQGaBJz7k]https://www.youtube.com/watch?v=C0XQGaBJz7k[/video]


By http://www.system-sounds.com/ which is a neat place to spend time - "a science-art outreach project that translates the rhythm and harmony of the cosmos into music and sound"

(Play Saturn's rings like a harp for example - it is special. :) )
 
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