Large Meteorite Impacts and Planetary Evolution V

EurekAlert! ^ | January 8, 2016 | Geological Society of America

[SunkenCiv]

Impact cratering is one of the most fundamental geological processes. On many planets, impact craters are the dominant geological landform. On Earth, erosion, plate tectonics, and volcanic resurfacing continually destroy the impact cratering record, but even here, the geological, biological, and environmental effects of impact cratering are apparent. Impact events are destructive and have been linked to at least one of the 'big five' mass extinctions over the past 540 million years. Intriguingly, impact craters can also have beneficial effects. Many impact craters are associated with economic metalliferous ore deposits and hydrocarbon reservoirs. This Special Paper from The Geological Society of America provides an up-to-date synthesis of impact cratering processes; the role of meteorite impacts in the origin of life, products, and effects; and the techniques used to study impact craters on Earth and other planetary bodies. This volume, edited by Gordon R. Osinski and David A. Kring, is a result of the Large Meteorite Impacts and Planetary Evolution V conference held in Sudbury, Canada, in August 2013. Table Of Contents

This is a Lunar Reconnaissance Orbiter Camera wide-angle color-shaded relief -- orthographic projection centered at 240 degrees longitude and 0 degrees latitude. [Credit: Source: NASA/GSFC/DLR/Arizona State University. Cover by the Geological Society of America.]

[SunkenCiv]

Large Meteorite Impacts and Planetary Evolution V (LMI V) August 5-8, 2013, Sudbury Canad

[SunkenCiv]

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[SunkenCiv]

[SunkenCiv]

A team of 14 scientists led by David Williams of Arizona State University's School of Earth and Space Exploration has completed the first global geologic and tectonic map of the asteroid Vesta. The work reveals that Vesta's history has been dominated by impacts from large meteorites.

The mapping was carried out using images from NASA's Dawn spacecraft, which orbited Vesta between June 2011 and September 2012. The images let scientists create high-resolution geological maps, revealing the variety of Vesta's surface features in unprecedented detail.

"The geologic mapping campaign at Vesta took about two and a half years to complete," says Williams. "The resulting maps enabled us to construct a geologic time scale of Vesta for comparison to other planets and moons."

The geologic map and timescale appear in a paper by Williams and others in the December 2014 issue of the journal Icarus. The issue also has 10 other papers reporting on Dawn's investigation of Vesta. In addition to Williams, the mapping effort was also led by R. Aileen Yingst of the Planetary Science Institute, Tucson, Arizona, and W. Brent Garry of NASA's Goddard Spaceflight Center, Greenbelt, Maryland.

The mappers found that Vesta's geologic time scale has been shaped by a sequence of large impact events. The biggest of these were the impacts that blasted the large Veneneia and Rheasilvia craters early in Vesta's history, and the Marcia crater late in its history.

In mapping an extraterrestrial object, scientists begin by studying its surface features to develop a relative chronology of events. They look to see which feature interrupts or disturbs other features, thereby placing them in a relative time sequence. Then, crater by crater, fracture by fracture, scientists build up a chronology of events.

But how long ago did specific events happen? An age in years is quite difficult to determine because the samples scientists have from Vesta -- a family of basaltic meteorites called HEDs, for howardite-eucrite-diogenite -- do not show a clear formation age (as dated by laboratory methods) that can be linked to specific features on the asteroid...

Williams' team concluded that the oldest surviving crust on Vesta predates the Veneneia impact, which has an age of 2.1 billion years (asteroid system) or 3.7 billion years (lunar system). The Rheasilvia impact likely has an age of around 1 billion years (asteroids) or 3.5 billion years (lunar).

"Vesta's last big event, the Marcia impact, has an age that's still uncertain," says Williams. "But our current best estimates suggest an age between roughly 120 and 390 million years." The difference, he explains, comes from which cratering model is used...

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Robert Burnham, Science writer, School of Earth and Space Exploration | ASU News | November 17, 2014

[ETL]

Another excellent job with this post.

[onedoug]

Flown over this one many times

[RedStateRocker]

Where’s a 5km meteorite when you need it?

[SunkenCiv]

3/4 mile wide, nearly 1/4 deep, formed by a 100 yard object, mind bogglingg.

[SunkenCiv]

Thanks ETL!

[SunkenCiv]

If a 5km hit on land anywhere on Earth, civilization would end, and 99% of humanity would be dead in a couple of months. The lucky ones would die instantly.

[SunkenCiv]

http://www.freerepublic.com/tag/lunarimpact/index

Red Planet’s Ancient Equator Located
http://www.freerepublic.com/focus/chat/1390424/posts

[ETL]

Red Planet's Ancient Equator Located

Mars apparently revolves on an unstable axis. They say this is what will ultimately happen with Earth once the Moon drifts far enough away. The Moon helps keep our 23.5 degree tilt angle stable. And it's slowly leaving us, at the rate of about 2 inches per year.

[gleeaikin]

When I was a young woman I was with my family driving through the Sudbury area. The landscape was ugly, barren and weird. The industrial pollution from the extensive ore deposits had left many strange colored areas. I had no idea then it was a crater.

By the time the moon moves far enough away to make our earth unstable, nothing resembling the current human race will exist, and that is if we are not as unlucky as the dinosaurs.

[SunkenCiv]

The Moon draws rotational momentum from the Earth; if that lasts long enough, the Moon will cease to be a satellite of the Earth. If it isn't enough, the Earth and Moon will be locked in a face-to-face resonance. The loss of the Moon will not cause instability, it will if anything lead to greater stability -- after the Moon wanders away far enough to wander off. The transition will be, uh, a little rocky, and that will last a while.

[ETL]

"The Moon has a stabilizing effect on Earth's obliquity [tilt angle]. Frequency map analysis suggests that, in the absence of the Moon, the obliquity can change rapidly due to orbital resonances and chaotic behavior of the Solar System, reaching as high as 90 degrees in as little as a few million years (also see Orbit of the Moon).[24][25]

However, more recent numerical simulations[26] suggest that even in the absence of the Moon, Earth's obliquity could be considerably more stable; varying only by about 20-25 degrees [23.5 + 20-25 deg].

The Moon's stabilizing effect will continue for less than 2 billion years.

If the Moon continues to recede from Earth due to tidal acceleration, resonances may occur which will cause large oscillations of the obliquity.[27]"

[27] Ward, W.R. (1982). "Comments on the Long-Term Stability of the Earth's Obliquity". Icarus 50: 444-448. Bibcode:1982Icar...50..444W. doi:10.1016/0019-1035(82)90134-8.

https://en.wikipedia.org/wiki/Axial_tilt
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"The pull of the moon is also slowing the Earth's rotation, an effect known as tidal braking, which increases the length of our day by 2.3 milliseconds per century.

The energy that Earth loses is picked up by the moon, increasing its distance from the Earth, which means the moon gets farther away by 3.8 centimeters annually.

The moon's gravitational pull may have been key to making Earth a livable planet by moderating the degree of wobble in Earth's axial tilt, which led to a relatively stable climate over billions of years where life could flourish."

http://www.space.com/55-earths-moon-formation-composition-and-orbit.html/

[ETL]

Stabilization of the Earth's obliquity by the Moon

J. Laskar, F. Joutel & P. Robutel

Astronomie et Systemes Dynamiques, Bureau des Longitudes, 77 Avenue Denfert-Rochereau, F75014 Paris, France

ACCORDING to Milankovitch theory [1,2], the ice ages are related to variations of insolation in northern latitudes resulting from changes in the Earth's orbital and orientation parameters (precession, eccentricity and obliquity).

Here we investigate the stability of the Earth's orientation for all possible values of the initial obliquity, by integrating the equations of precession of the Earth. We find a large chaotic zone which extends from 60 deg to 90 deg in obliquity.

In its present state, the Earth avoids this chaotic zone and its obliquity is essentially stable, exhibiting only small variations of +/- 1.3 deg around the mean value of 23.3 deg.

But if the Moon were not present, the torque exerted on the Earth would be smaller, and the chaotic zone would then extend from nearly 0 deg up to about 85 deg.

Thus, had the planet not acquired the Moon, large variations in obliquity resulting from its chaotic behaviour might have driven dramatic changes in climate.

In this sense one might consider the Moon to act as a potential climate regulator for the Earth.

http://www.nature.com/nature/journal/v361/n6413/abs/361615a0.html

[SunkenCiv]

It’s just uniformitarian gobbledygook. Nice ‘climate change’ angle in there too.

It’s always amusing to see, coming as I do from a long familiarity with uniformitarian objections to Velikovsky, that everything in their little outlook results just-so in stability, because any change at all in what is seen would have led inevitably to chaos.

I like their use of the phrase “acquired the Moon” — the Moon is clearly not the result of a large impact on the proto-Earth, but a later ‘foundling’, captured after a series of encounters made over some millions of years.

[ETL]

I like their use of the phrase "acquired the Moon" - the Moon is clearly not the result of a large impact on the proto-Earth, but a later 'foundling', captured after a series of encounters made over some millions of years.

Nearly all experts today believe the Moon was the result of a very early collision between a Mars-sized planet and the Earth.

[ETL]

It's just uniformitarian gobbledygook. Nice 'climate change' angle in there too.

Yes, but the 'climate change' they're referring to of course would be a totally natural thing. Big difference from the man-made 'climate change' BS that the global governance crowd is trying to scare people with.

[SunkenCiv]

Yes, you're right, no doubt about it -- but all those experts are dead wrong . That's based not merely on the implausibility of their model, but also on fossil evidence (there really is some) as well as isotope ratios from lunar surface samples (which are themselves, like the fossils, wrongly used to prop up their impact model). It's a little disorienting, I realize, considering what a deep interest I have in the consequences of impact. :')