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Earth Impacts and Why You Might Care Craters produced by asteroid impacts are ubiquitous throughout

the Solar System

Earth's Moon

Saturn's icy moon Rhea

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Earth Impacts and Why You Might Care Craters produced by asteroid impacts are ubiquitous throughout

the Solar System

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Earth Impacts and Why You Might Care Bombardment is a natural consequence of the cleanup of the

Solar System following the initial accretion of the planets.

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Earth Impacts and Why You Might Care What was a “heavy bombardment” has tapered off to a “light

peppering”

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Earth Impacts and Why You Might Care The Solar System is still full of potential large impactors.

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no, no, NO, NO, NO!!!!!!!

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Earth Impacts and Why You Might Care The Earth has been impacted as much as the Moon (actually more

because of its stronger gravity) The (thin) atmosphere does little to protect against large impactors.

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Earth Impacts and Why You Might Care The Earth has been impacted as much as the Moon (actually more

because of its stronger gravity) The (thin) atmosphere does little to protect against large impactors.

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Earth Impacts and Why You Might Care Erosion and resurfacing have erased all but the most recent

impact scars.

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The Arrival Rate of Impactors vs. Size A beachball-sized object strikes Earth daily. Objects 10

kilometers in size strike once every 100 million years.

− Asteroid collisions produce lots of small fragments and a few big ones.

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The Arrival Rate of Impactors vs. Size A beachball-sized object strikes Earth daily. Objects 10

kilometers in size strike once every 100 million years.

− Objects smaller than a few tens of meters in size don't reach the ground intact.

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The Delivered Energy Can be Huge Traveling at speeds up to 10's of kilometers per second, the

kinetic energy of these objects is substantial.

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Sikote-Alin U.S.S.R. - December 2, 1947• Approximately 100 tons of iron fell from the sky.

• The object exploded in the atmosphere and small pieces littered the ground.

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Large Impacts and Mass Extinctions

The fossil record contains notable episodes where many (if not most) of the species on Earth disappeared.

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Large Impacts and Mass Extinctions The frequency of these events is consistent with the arrival rate of

impactors 10 kilometers in size (roughly every 100 million years).

− Such an impactor triggers global fires and contaminates the stratosphere with enough dust to blot out the Sun for years.

− The food chain collapses and many species die out.

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Large Impacts and Mass Extinctions The frequency of these events is consistent with the arrival rate of

impactors 10 kilometers in size.

− Evidence that such events happen includes the presence of excess iridium in geologic layers that mark mass extinctions.

− Iridium is rare on the Earth's surface but common in meteorites.

− A worldwide iridium rich layer is coincident with the demise of the dinosaurs – The Cretaceous-Tertiary (KT) boundary

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The Demise of the Dinosaurs If dinosaurs were wiped out by an impact 65

million years ago there had better be better evidence than some extra iridium in the ground..... and there is.

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The Demise of the Dinosaurs If dinosaurs were wiped out by an impact 65 million years ago

there had better be better evidence than some extra iridium in the ground..... and there is... a buried impact crater in the Yucatan dating back 65 million years.

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The Demise of the Dinosaurs If dinosaurs were wiped out by an impact 65 million years ago

there had better be better evidence than some extra iridium in the ground..... and there is... melted glass beads formed in the impact are spread across North America and embedded in the KT boundary.

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The Demise of the Dinosaurs

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Well, it's a good thing that can't happen to us..........

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Assessing the Odds Rank the items below (which include three different impact

hazards) from “least likely” to “most likely”.

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The Modern Impact Hazard 65 million years is not all that long ago. The Solar System is just as

messy. We run the same risks as the Dinosaurs. A mass extinction level impact is improbable, but smaller impacts that

might have devastating consequences happen much more frequently.

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The Modern Impact Hazard The last major event with significant consequences (destruction of

a city-sized area) occurred only a century ago.

− Tunguska, Siberia in 1908

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The Modern Impact Hazard Every few 10's of thousands of years an object a few hundred

meters in size arrives depositing the energy of a few hundred thermonuclear explosions.

− Such an impact in an ocean (70% of the Earth's surface) would set off devastating tidal waves that would destroy coastal cities.

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Impacts Close to Home• 35 million years ago...

•

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Shouldn't We Do Something about It?

We live during the first time in Earth history where we can modify the odds in our favor.

− Seek out potentially hazardous asteroids.

− Find the one(s) that are on a direct collision course

− Nudge them so that they miss the Earth.

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Shouldn't We Do Something about It?

We live during the first time in Earth history where we can modify the odds in our favor.

− Seek out potentially hazardous asteroids.

− Find the one(s) that are on a direct collision course

− Nudge them so that they miss the Earth.

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Shouldn't We Do Something about It?

We live during the first time in Earth history where we can modify the odds in our favor.

− Seek out potentially hazardous asteroids.

− Find the one(s) that are on a direct collision course

− Nudge them so that they miss the Earth.

http://neo.jpl.nasa.gov/

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Shouldn't We Do Something about It?

We live during the first time in Earth history where we can modify the odds in our favor.

− Seek out potentially hazardous asteroids.

− Find the one(s) that are on a direct collision course

− Nudge them so that they miss the Earth.

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A Success of the System: 2008 TC3 19 hours before Earth impact the Catalina Sky

Survey picked up a small asteroid, the size of a pickup truck, headed for the African Nubian desert.

http://neo.jpl.nasa.gov/news/news163.html

http://www.nasa.gov/topics/solarsystem/tc3/

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A Success of the System: 2008 TC3 The observation enabled the prediction of the impact location.

http://neo.jpl.nasa.gov/news/news163.html

http://www.nasa.gov/topics/solarsystem/tc3/

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A Success of the System: 2008 TC3 The observation enabled the prediction of the impact location....

and recovery of samples.

http://neo.jpl.nasa.gov/news/news163.html

http://www.nasa.gov/topics/solarsystem/tc3/

http://www.nature.com/nature/journal/v458/n7237/full/nature07920.html

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A Success of the System: 2008 TC3 The observation enabled the prediction of the impact location....

and recovery of samples.

http://neo.jpl.nasa.gov/news/news163.html

http://www.nasa.gov/topics/solarsystem/tc3/

http://www.nature.com/nature/journal/v458/n7237/full/nature07920.html

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Shouldn't We Do Something about It?

We live during the first time in Earth history where we can modify the odds in our favor.

− Seek out potentially hazardous asteroids.

− Find the one(s) that are on a direct collision course

− Nudge them so that they miss the Earth.

Asteroid Apophis 320 meters in diameter April 13, 2029

http://neo.jpl.nasa.gov/news/news149.html

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Shouldn't We Do Something about It?• At what cost?

– An investment of a few hundred million dollars is required to find the threats.

– Congressional mandate: Find all Potentially Hazardous Asteroids >140 meters by 2020.

http://science.nasa.gov/headlines/y2009/15sep_ninjaastronomy.htm

http://science.nasa.gov/science-news/science-at-nasa/2010/26mar_darkasteroids/

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Things that Cost around 200 Million Dollars• Production cost of a (scientifically horrendous) movie about the

asteroid impact hazard.

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Your Favorite Baseball Player

Alex Rodriguez, $275,000,000 (2008-17)

Alex Rodriguez, $252,000,000 (2001-10)

Derek Jeter, $189,000,000 (2001-10)

Mark Teixeira, $180,000,000 (2009-16)

CC Sabathia, $161,000,000 (2009-15)

Manny Ramirez, $160,000,000 (2001-08)

Miguel Cabrera, $152,300,000 (2008-15)

Todd Helton, $141,500,000 (2003-11)

Johan Santana, $137,500,000 (2008-13)

Alfonso Soriano, $136,000,000 (2007-14)

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1/10th of an Aircraft Carrier

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1/3 of a Space Shuttle Launch

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The JPJ -or- The South Lawn• 131 and 105 million respectively.

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Shouldn't We Do Something about It?• We live during the first time in Earth history where we can modify

the odds in our favor.

– - The Dinosaurs were not so lucky.

– - An impact 65 million years ago changed the course of evolution of life on Earth.

– - Dinosaurs – the most successful set of advanced animals ever to live on Earth (surviving for more that 100 million years), disappeared overnight.

– - Mammals, and ultimately humans, took their place.

–

• We owe our position as the dominant species on Earth to a random cosmic event 65 million years ago.

– - Have other “Earth's” been so lucky (or unlucky??)

–

• The difference between us and the Dinosaurs...

• We can do something about it.

–

–

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Shouldn't We Do Something about It?

• We live during the first time in Earth history where we can modify the odds in our favor.

– Seek out potentially hazardous asteroids.

– Find the one(s) that are on a direct collision course

– Nudge them so that they miss the Earth.

• Nuclear explosion nearby

• Paint one side white!

• Gravity tractor

http://www.unisci.com/stories/20022/0408022.htm

If we discover an offensive asteroid early enough time is on our side – a tiny push is enough for a “miss”.

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Shouldn't We Do Something about It?

We live during the first time in Earth history where we can modify the odds in our favor.

− Seek out potentially hazardous asteroids.

− Find the one(s) that are on a direct collision course

− Nudge them so that they miss the Earth.

Nuclear explosion nearby Paint one side white! Gravity tractor

http://www.newscientist.com/article/dn14414-gravity-tractor-could-deflect-asteroids.html

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