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Asteroid Strikes 'Increase Threefold Over Last 300 Million Years,' Survey Finds (theguardian.com)
According to a survey of asteroid craters at least 6.2 miles wide, the number of asteroids slamming into Earth has nearly tripled since the dinosaurs first roamed. "Researchers worked out the rate of asteroid strikes on the moon and the Earth and found that in the past 290 million years the number of collisions had increased dramatically," reports The Guardian. "Before that time, the planet suffered an asteroid strike about once every 3 million years, but since then the rate has risen to once nearly every 1 million years." From the report: The findings suggest that the dinosaurs may have been unfortunate in evolving 240 million years ago, just as the odds of being wiped out by a stray asteroid were ramping up. It was one of those impacts, on top of other factors, that did for the beasts 66 million years ago. Many scientists had assumed that asteroid strikes were a rare but constant threat in Earth's deep history, but the latest study challenges that belief.
Writing in the journal Science, the researchers describe how they turned to the moon to examine the violent history of Earth. The Earth and moon are hit by asteroids with similar frequency, but impact craters on Earth are often erased or obscured by erosion and the shifting continents which churn up the crust. On the geologically inactive moon, impact craters are preserved almost indefinitely, making them easier to examine. 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. The dates revealed that the moon, and by extension the Earth, has suffered more intense asteroid bombardment in the past 290 million years than at any time in the previous billion. On Earth there are hardly any impact craters older than 650 million years, most likely because they were eroded when the planet became encased in ice in an event known as Snowball Earth.
Writing in the journal Science, the researchers describe how they turned to the moon to examine the violent history of Earth. The Earth and moon are hit by asteroids with similar frequency, but impact craters on Earth are often erased or obscured by erosion and the shifting continents which churn up the crust. On the geologically inactive moon, impact craters are preserved almost indefinitely, making them easier to examine. 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. The dates revealed that the moon, and by extension the Earth, has suffered more intense asteroid bombardment in the past 290 million years than at any time in the previous billion. On Earth there are hardly any impact craters older than 650 million years, most likely because they were eroded when the planet became encased in ice in an event known as Snowball Earth.
Seems to me that the cloud of debris that surrounds our solar system (and likely most others as well) would be unstable as stars pass by each other.
"His name was James Damore."
How do we *know* the rate of micrometeorite bombardment is constant and hasn't dropped in intensity by a third in recent (geological/selenological) times?
I don't subscribe to RMS's GNUtopian vision.
That's a bit of a stretch, but trump is one of the major threats to human extinction.
So what you are calling for is human extinction? Cant have any threats to it?
You sound like those Christians yearning for Armageddon.
"His name was James Damore."
Evidence of 300 million year old asteroid craters is many times more likely to have been destroyed. Other scientific papers have pointed to a much more chaotic solar system earlier in its history, so the trend may in fact be in the opposite direction, just the evidence no longer exists.
No, no, no. You have the culprit right, but the fix is clearly higher taxes. That's one of the three universal fixes:
1. If it's stuck and has to move: WD-40
2. If it moves and needs to be fixed: Ductape
3. If it has the word 'climate' in it: Tax!
To Terminate, or not to Terminate, that's the question - SCSIROB
Who do you think is the reading audience here, that they would be so badly thrown off by using km? I think /. readers are smarter than that.
--
.nosig
Probably major collisions between moons produces an increase in asteroid impacts for millions of years afterwards, until gravity eventually clears out the debris.
I've abandoned my search for truth; now I'm just looking for some useful delusions.
Unfortunately, Trump has diverted all the funding to combating hemorrhoid growth... he's a little confused!
I've abandoned my search for truth; now I'm just looking for some useful delusions.
I don't believe it. In my more than half century of life I've never heard of the -fold suffix being used in the way you describe, and quick search only turns up references (including a Wikipedia page) that equate it with "times". If you have any source for your assertion, I'd like to see that.
Has anyone tied this, snowball earth and the great nonconformity together? the eons roughly match.
Yes there was a news story about this three weeks ago.
Starships were meant to fly, Hands up and touch the sky - Nicky Minaj
You sound like those Christians yearning for Armageddon.
They haven't learned their lesson from 1998? What good will a remake do?
Ezekiel 23:20
Sociopaths, we call them, and there seem to be a lot of them about recently. Of course, they are also idiots if they think a single politician can somehow destroy the most adaptive species every to arise. That also has a name, Trump Derangement Syndrome.
I didn't even know there was a union.
Have gnu, will travel.
The CO2 buildup started when dinosaurs started driving SUVs and using coal-fired generators. It's an obvious case of dinogenic global warming.
Contribute to civilization: ari.aynrand.org/donate
What else could it be?
"Consensus" in science is _always_ a political construct.