![Impact [image credit: karbalion.com]](https://tallbloke.files.wordpress.com/2015/10/impact1.jpeg)
Impact [image credit: karbalion.com]
Another puzzle for planetary cycle researchers to ponder, as this phys.org report explains.
– – –
Mass extinctions occurring over the past 260 million years were likely caused by comet and asteroid showers, scientists conclude in a new study published in Monthly Notices of the Royal Astronomical Society. For more than 30 years, scientists have argued about a controversial hypothesis relating to periodic mass extinctions and impact craters—caused by comet and asteroid showers—on Earth.
In their MNRAS paper, Michael Rampino, a New York University geologist, and Ken Caldeira, a scientist in the Carnegie Institution’s Department of Global Ecology, offer new support linking the age of these craters with recurring mass extinctions of life, including the demise of dinosaurs. Specifically, they show a cyclical pattern over the studied period, with both impact craters and extinction events taking place every 26 million years.
This cycle has been linked to periodic motion of the sun and planets through the dense mid-plane of our galaxy. Scientists have theorized that gravitational perturbations of the distant Oort comet cloud that surrounds the sun lead to periodic comet showers in the inner solar system, where some comets strike the Earth.
To test their hypothesis, Rampino and Caldeira performed time-series analyses of impacts and extinctions using newly available data offering more accurate age estimates. “The correlation between the formation of these impacts and extinction events over the past 260 million years is striking and suggests a cause-and-effect relationship,” says Rampino.
Specifically, he and Caldeira found that six mass extinctions of life during the studied period correlate with times of enhanced impact cratering on Earth. One of the craters considered in the study is the large (180 km diameter) Chicxulub impact structure in the Yucatan, which dates at about 65 million years ago—the time of a great mass extinction that included the dinosaurs.
Moreover, they add, five out of the six largest impact craters of the last 260 million years on earth correlate with mass extinction events. “This cosmic cycle of death and destruction has without a doubt affected the history of life on our planet,” Rampino observes.
Provided by New York University
Source: Scientists find link between comet and asteroid showers and mass extinctions
Tallbloke's Talkshop 
When are we due the next one? Aren’t we near the galactic midplane at the moment?
*Dons hat*
That image reminds me of Melancholia
If there was one 65 million years ago, every 26m. years since is 39m., 13m….we should be okay for another 13 million years. Phew 😉
Possible fly in the ointment…a major impact that didn’t lead to a mass extinction – but later volcanism did.
‘Keller and her colleagues most recently looked at the geological records in India, Texas and Mexico to help pin down when the impact and volcanism occurred in relation to the K-T event. The work was supported by the National Science Foundation.
By examining sediment layers, the team found that the crater impact appears to have occurred about 300,000 years before the K-T boundary, with virtually no effects to biota.
“There is essentially no extinction associated with the impact,” Keller said.
In contrast, the main thrust of the Deccan volcanism occurred “just before the K-T boundary,” said geophysicist Vincent Courtillot of the University of Paris’
http://www.livescience.com/3165-dinosaur-killer-volcanism-asteroid.html
Against that it could be argued that dating techniques re 65m. years ago have limited accuracy.
I remember reading about this in Scientific American around ten years ago.
Recall 32 million years from Shaviv’s classic:
http://www.sciencebits.com/sights-field-trip-milky-way
On another timescale, a proposed solar driven 270 year storminess cycle
http://www.sciencedirect.com/science/article/pii/S0277379115301335
Big storm events represent a major risk for populations and infrastructures settled on coastal lowlands. In the Western Mediterranean, where human societies colonized and occupied the coastal areas since the Ancient times, the variability of storm activity for the past three millennia was investigated with a multi-proxy sedimentological and geochemical study from a lagoonal sequence. Mappings of the geochemistry and magnetic susceptibility of detrital sources in the watershed of the lagoon and from the coastal barriers were undertaken in order to track the terrestrial or coastal/marine origin of sediments deposited into the lagoon. The multi-proxy analysis shows that coarser material, low magnetic susceptibility, and high strontium content characterize the sedimentological signature of the paleostorm levels identified in the lagoonal sequence. A comparison with North Atlantic and Western Mediterranean paleoclimate proxies shows that the phases of high storm activity occurred during cold periods, suggesting a climatically-controlled mechanism for the occurrence of these storm periods. Besides, an in-phase storm activity pattern is found between the Western Mediterranean and Northern Europe. Spectral analyses performed on the Sr content revealed a new 270-year solar-driven pattern of storm cyclicity. For the last 3000 years, this 270-year cycle defines a succession of ten major storm periods (SP) with a mean duration of 96 ± 54 yr. Periods of higher storm activity are recorded from >680 to 560 cal yr BC (SP10, end of the Iron Age Cold Period), from 140 to 820 cal yr AD (SP7 to SP5) with a climax of storminess between 400 and 800 cal yr AD (Dark Ages Cold Period), and from 1230 to >1800 cal yr AD (SP3 to SP1, Little Ice Age). Periods of low storm activity occurred from 560 cal yr BC to 140 cal yr AD (SP9 and SP8, Roman Warm Period) and from 820 to 1230 cal yr AD (SP4, Medieval Warm Period).
It still wouldn’t hurt to have the capability to destroy or change the course of any such Asteroids/Comets.
A much better investment than “Climate Change Mitigation” because it means you improve Space capability.
ACO, where’s Bruce Willis when you need him?
Nir Shaviv says:
‘Passages through the galactic arms appear to have a 145 million year period (see http://www.sciencebits.com/ice-ages). The oscillation perpendicular to the galactic plane gives rise to the 32 million year oscillation (which is modulated by the radial motion of the solar system in the galaxy).’
http://www.sciencebits.com/sights-field-trip-milky-way#comment-1910178927
145×32 / (145+32) = 26.2~ (million)
This post: ‘Specifically, they show a cyclical pattern over the studied period, with both impact craters and extinction events taking place every 26 million years.’
Is anyone in contact with Shaviv?
I’m curious to see his commentary.
Big difference with chicxulub is a worldwide ejecta horizon not apparent for other extinctions/impacts, including the 256mya Permian. Ejecta analysis from KPg suggests low angle +- 20 degrees SSE. Maybe in direct impacts the ejecta blows out to space?
Paul, the article by Nir Shaviv you linked upthread said the time period reduced as better measurement came along. Maybe the period is down from 32My to 26 by now?
oldbrew:
the chances are that the impact triggered a major eruption from an existing volcanic area.
The impact theory had all the hallmarks of its time, nuclear winter, vegetation being burnt world-wide (eliminating herbivores, hence mass starvation) generating CO2 causing global warming and ocean acidification etc.
Since the temperature seems to have gone done, and CO2 could NOT have acidified the oceans some other effect extended mass extinction to the oceans. Volcanic sulphur gases are the logical choice. With volcanic action from the Siberian traps implicated in the even bigger Permian extinctions and the recent dating of a hadrosaur to 100,000 years after the impact, I think that the effect of the impact alone has been exaggerated.
Graeme: ‘generating CO2 causing global warming’
All historical records show CO2 increases lagging warming by as much as 800 years, so that idea won’t work.
Yep. Except the period is supposed to be 35 million years.
http://www.nature.com/news/did-dark-matter-kill-the-dinosaurs-1.14839
Which is pretty much inconsistent with a 26 million years periodicity.
see:
Physical Review Letters 112, 161301 – Published 21 April 2014
DOI: 10.1103/PhysRevLett.112.161301
Dark Matter as a Trigger for Periodic Comet Impacts
Lisa Randall &. Matthew Reece
Ah, dreams, sweet dreams.
Some support for the 26m year periodicity here:
http://mb-soft.com/public/galaxy.html
“It has long been noted that the Moon has many more large impact craters in its southern hemisphere than in the northern. The same has been found true of the planet Mercury. Possibly even for Mars and some satellites. This new approach may provide a logical explanation for that long-known asymmetry, that the (leading) south side of the Moon, Earth, Mercury, Mars, etc, would have been susceptible to far faster collision impacts than would be true of the trailing side. We note the same effect every night in that evening meteors tend to be less brilliant than early morning meteors, because of being on the trailing/leading sides of the Earth in its orbital motion.”
Would south side also apply the earth southern hemisphere?
Hmm…