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How to Defend Earth From Asteroids

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Apocalypse Now
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« on: December 23, 2012, 03:50:29 pm »


How to Defend Earth From Asteroids



Phil Plait


The Earth sits in a cosmic shooting gallery.

Millions of asteroids orbit the Sun, some on paths that cross that of Earth. These range in size from grains of sand -- which create beautiful but harmless shooting stars when they burn up in our atmosphere -- to rocks the size of football stadia and even cities themselves. One such asteroid, 10 kilometers across, impacted the Earth 65 million years ago, and the resulting devastation wiped out the dinosaurs essentially overnight.

We know there are no rocks that big headed our way anytime soon, at least not for centuries. But it only takes one asteroid, 100 or so meters across, impacting the Earth to explode with the force of a dozen nuclear weapons. This is something we might wish to avoid!

So what do we do?

Find 'em

Step 1 is obvious enough: Find them. Smaller asteroids around 100 meters in diameter are tough to see because space is vast and distances large. We need big telescopes that can sweep across large areas of sky rapidly and find those moving targets. The good news is we have 'scopes like that, and we're building more.

    It only takes one asteroid, 100 or so meters across, impacting the Earth to explode with the force of a dozen nuclear weapons. This is something we might wish to avoid! - Phil Plait

Still, some of these cosmic bullets are on orbits that make them very tough to spot. They stay near the Sun, making them hard to observe from the ground. There are two solutions to that. One is to build a spacecraft that travels in a path closer to the Sun, so now it's looking away from the Sun rather than toward it to spot asteroids. Another is to launch a telescope that does the same thing but stays near Earth. Both have their advantages, and the good news again is that both of these methods are being actively pursued!

The B612 Foundation is a group of astronomers, astronauts and engineers who investigate the Asteroid Problem. They are seeking private donations to build Sentinel, a spacecraft that will travel on a Venus-like orbit, closer to the Sun, to look for hazardous asteroids.

NASA is looking into building the near-Earth mission, which is called NEOCam (for Near-Earth Object Camera). Both spacecraft would be tuned to look in the infrared, where warm asteroids give themselves away against the cold of space, and both expect to find as many as 90 percent of Earth-approaching asteroids bigger than 140 meters in size. Sentinel can look in regions of space NEOCam can't see, but NEOCam, being closer to Earth, can scan the skies faster and transmit the data more efficiently to Earth. Together, they will make a formidable team watching the skies.



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« Reply #1 on: December 23, 2012, 03:51:31 pm »

Kill 'em

Suppose that NEOCam or Sentinel, or some ground-based survey, finds an asteroid with our number on it. What do we do?

One idea I'm fond of is the "kinetic impactor plus gravity tug," which I outline in the video. Basically, a space probe is sent to the killer asteroid at full speed, and slams into it. The force of the impact changes the velocity of the rock slightly, hopefully enough so that it will miss the Earth.

Just to make sure -- and also to make sure the asteroid doesn't simply circle the Sun a few more times and hit us at some later date -- a second probe is sent along, hitchhiking with the impactor. It can move into a station-keeping position near the rock, using its own gravity to very gently tug the rock into a safe orbit. This takes a lot of time, so the more lead-time we have, the better. In fact, it takes a lot of lead-time to build and launch the probes, as well as get to the asteroid. That's why finding all these asteroids as quickly as possible is so important.

Unfortunately, we don't have missions like these built and ready to go. We don't even have them designed! B612 is working on that, but NASA has not seriously investigated this kind of mission. Of course, NASA has a finite budget, so trying to find the money necessary to do this -- hundreds of millions if not billions of dollars -- is just not possible for them unless Congress and the president take it seriously and raise NASA's budget to do it.
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« Reply #2 on: December 23, 2012, 03:52:46 pm »

What, me worry?

Right now, we don't know of any asteroids on an impact course with Earth that could do us serious, global damage. There is a handful we know of that are being watched carefully, but in all those cases the odds of impact are pretty low. If it helps, I'm not lying awake at night fretting about any of them.

I wrote a book, Death from the Skies!, and the first chapter was on asteroid impacts. I wound up spending some quality time thinking about the effects of the impact that wiped out the dinosaurs. I have a pretty vivid imagination, and had colorful, terrifying scenes of that day going through my mind as I wrote the grim details down. I've always been fascinated with big disasters -- who isn't? -- but that experience cemented my desire to be involved with all this. After all that, I suppose I would say I'm not worried, but I am concerned. Calculating the odds of a big impact helped, since they are so infrequent.

... but that's not to say no rock will ever hit us. Given enough time, and our inaction, an impact is inevitable. But we're clever animals, us humans, smarter than the dinosaurs ever were. We are just waking up to the dangers in the sky, and I think we're intelligent enough to recognize the threat and take it seriously. We've already begun taking steps in that direction. It will take time, and lots of expertise, and of course a lot of money. But that'll be a pittance compared to the cost of doing nothing.

In the case of astronomy, as is true with most of science, we don't spend money on it. We invest in it.

Ideas are not set in stone. When exposed to thoughtful people, they morph and adapt into their most potent form.
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« Reply #3 on: December 23, 2012, 03:54:21 pm »

I don't know. Maybe give everybody a gun, so they can shoot it to pieces?
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« Reply #4 on: December 23, 2012, 03:56:23 pm »


Mario Livio

Asteroids Giveth and Asteroids Taketh Away


If dinosaurs could have left written records, then we all probably would have read by now the horror stories describing the mass extinction of some 65 million years ago. Such first-hand documents would also have put an end to the debate on whether it was a large asteroid impact or increased volcano activity that brought about the demise of the dinosaurs. In any case, there is no doubt that a huge asteroid impact on Earth would be devastating to many life forms. However, we often forget that asteroid impacts may have played a crucial role in the emergence of life on Earth, and possibly even in the fact that humans are here to talk about them!

How are asteroids potentially important for life? First, recent studies by astrophysicist Rebecca Martin and myself have shown that the Earth most likely formed in the dry region of the disk of gas and dust around the young Sun. This explains why less than one percent of the Earth's mass is water. Consequently, the water (that we believe was essential for life to emerge) had to be brought to Earth, and the most likely delivery agents were asteroids (although comets, and the interaction between the magma and the atmosphere, may have also played a role). Second, heavy elements that are important for life -- such as iron -- may also have been delivered to the Earth's crust by asteroids (the iron in the initial molten Earth sank to the core). Third, some researchers have even suggested that primitive life forms, or the building blocks for life, may have arrived to Earth by way of asteroids. Fourth, the formation of the Earth's relatively large Moon is also thought to have ensued from a collision with a large body (although perhaps planet-sized and not an asteroid). The Moon stabilized the Earth's rotation axis against chaotic motion that would have resulted in weather extremes that could not have been "healthy" for life. Finally, one could wildly speculate that were it not for the extinction of the dinosaurs -- large, ferocious animals with extremely small brains -- mammals would not have become the dominant clade, and intelligent life might not have emerged. The key point is that even if only one of these potential roles for asteroids in the evolution of life on Earth is true, then the existence of an asteroid belt may be a necessary condition for intelligent life in extrasolar systems.

    The key point is that even if only one of these potential roles for asteroids in the evolution of life on Earth is true, then the existence of an asteroid belt may be a necessary condition for intelligent life in extrasolar systems. - Mario Livio

There is, however, another issue that must be considered. Observations of extrasolar planets have shown that giant planets often migrate inwards through the protoplanetary disk. Such a migration can scatter the asteroid belt (if one had formed at all), with asteroids being either accreted by the central star, or ejected to large orbits. Consequently, systems in which significant migration has occurred are not expected to harbor a compact asteroid belt. At the other extreme, if the giant planet that was responsible for the formation of the asteroid belt in the first place (by gravitationally preventing a planet from forming) does not migrate at all, the asteroid belt may be too massive. Frequent impacts from such a belt would be harmful for life. In other words, for life to evolve, a just-right asteroid belt may be needed (Figure 1). In this respect, the solar system found itself in the "Goldilocks" paradigm, with Jupiter having migrated just enough to deplete the asteroid belt, but not destroy it.

Rebecca Martin and I have shown that among the giant extrasolar planets observed to date, about four percent appear to have the right conditions for a potentially favorable asteroid belt. My guess would be that terrestrial planets in the habitable zones (that allow for liquid water on the planet's surface) of those systems are good candidates for life.

Concerning the Earth, we should do everything we can to prevent future impacts, but at the same time, it is quite possible that we should be thankful for past ones.

Ideas are not set in stone. When exposed to thoughtful people, they morph and adapt into their most potent form.
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« Reply #5 on: December 23, 2012, 03:57:29 pm »

Watch this:

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« Reply #6 on: December 23, 2012, 03:59:25 pm »


Mark Boslough

Global Catastrophes in Perspective

Sixty five million years ago, the dinosaurs had a bad day. Phil Plait's talk, "How to defend Earth from asteroids," describes how our own species might be able to avoid a repeat performance. Scientists take this threat is seriously. It is the subject of a recent National Research Council report "Defending Planet Earth" and the upcoming Planetary Defense Conference in Flagstaff, Arizona (April 15-19, 2013). How worried should we be?

Human beings are notoriously bad at estimating personal risk. Here's a list of threats:

Asteroid impact
Mayan "2012" Apocalypse
Earthquake
Shark Attack
Motor vehicle accident
Fireworks accident
Airplane crash
Food poisoning by botulism
Drowning

    It would be the ultimate irony if we developed the technology to defend our planet from asteroids, but not from our own behavior. - Mark Boslough

I want you to put them in order of how likely you think they are to kill the average American. See if you can guess the odds of dying from each of them. Don't peek ahead!

We're even worse at estimating the likelihood of a global catastrophe. How do we calculate our personal probability of being killed by an asteroid? First, we have to know how many are moving in orbits that take them close to the Earth. Next we have to know the distribution of sizes (there are a lot more small ones than big ones). We need to estimate how many there are in each range of diameters. Finally, we have to have an idea of how many people would die from impacts of various sizes. Big asteroids -- like the one that wiped out the dinosaurs -- are a lot deadlier than the small ones that explode in the air.

The first serious attempt to quantify the asteroid impact risk was done twenty years ago. A team led by my colleague David Morrison published the "Morrison Report," which came to the startling conclusion that each of us was as likely to be killed by a rock from space as we were to die in a commercial aviation accident. The good news was that most of the threat was from the biggest ones -- about two thirds of a mile or more in diameter. Those are the easiest to detect and track, and there are only about a thousand of them.

At the recommendation of the report, astronomers conducted a survey to discover those big ones to find out if any of them were on a collision course. The strategy was similar to looking both ways when you come to a busy street. If there's nothing coming, you proceed. Otherwise, you take action (by waiting to cross, or by deflecting the asteroid).

We lucked out. After 90 percent completion, there are no large asteroids that can hit us in the foreseeable future. That doesn't mean we should stop looking, of course. A large impact would still lead to a catastrophic climate change that could cause the collapse of agriculture, spelling the end of civilization and the world as we know it. And we've barely made a dent in the hundreds of thousands of smaller objects that have the capacity to wipe out a city and kill millions.

How does this compare to the other planetary threats? The one we've been hearing about lately is the apocalypse that was supposedly to coincide with the end of the Mayan calendar on Dec. 21, 2012. But that's just a hoax. The same David Morrison who quantified the impact risk has been a tireless debunker of the 2012 myth. By the time you read this essay, you will know he was right about that, too.

One way to compare various threats is to determine how many people die, on average, every year. We can use a theoretical number, based on calculations, for asteroids, and compare it to numbers compiled by the World Health Organization. Here's the resulting table, based on one in Defending Planet Earth:
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« Reply #7 on: December 23, 2012, 04:00:16 pm »

Cause       Expected Deaths Per Year
Shark attacks       3-7
Asteroids       91
Firearms accidents       2,500
Earthquakes       36,000
Climate Change       150,000
Malaria       1,000,000
Traffic accidents       1,200,000
Air pollution       2,000,000
HIV/AIDS       2,100,000
Tobacco       5,000,000


Asteroids and climate change are the only two threats in the table that can have abrupt and global consequences, and to which everyone on the planet is exposed, regardless of their lifestyle or personal behavior. In principle, they are both preventable. In both cases mitigation would require international agreements and cooperation. But would such collaboration even be possible if a threatening asteroid were discovered, or would we be bogged down in the same kind of denial and obstruction that has prevented action on climate change?

Evidence from Greenland ice cores and other paleoclimate data show that spontaneous and extreme climate changes take place much more frequently than large impacts and on time scales that can exceed human adaptive capacities. Asteroid impacts are rare events, but abrupt climate changes are common by comparison. Only 13,000 years ago, the North American megabeasts -- including woolly mammoths, saber-toothed cats, giant sloths -- also had a very bad day. Well, at least a bad millennium. It was so bad that some scientists have mistakenly attributed that mass extinction to a 2 ½ mile-wide comet explosion. That idea has also been debunked by many scientists, including -- you guessed it -- David Morrison.

Fortunately, there are only around 30 undiscovered asteroids larger than a mile in diameter. The probability of impact by one of these before the end of the century is 0.0005 percent. On the other hand, recent research suggests a 2 percent probability of global catastrophe from anthropogenic climate change by the end of this century. It is reasonable to suggest that a human-caused climate catastrophe is at least 40,000 times more probable than an asteroid catastrophe. And for anyone who has looked at the temperature records for this year, we can't say we haven't been warmed!

The scary lesson of the North American megabeast extinction is that it doesn't take a giant impact to create a bad day. The Earth is susceptible to catastrophic climate changes that can be triggered by much smaller events. We are now in the process of disrupting the Earth's energy balance with a speed and magnitude that only the largest impacts have achieved in the past. It would be the ultimate irony if we developed the technology to defend our planet from asteroids, but not from our own behavior. And if we don't do something about it soon, we are in for a very bad century.
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« Reply #8 on: December 23, 2012, 04:00:36 pm »

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« Reply #9 on: December 23, 2012, 04:01:05 pm »

Finally, here are the answers to the quiz:

Motor vehicle accident (1 in 90)
Drowning (1 in 9,000)
Airplane crash (1 in 30,000)
Earthquake (1 in 130,000)
Fireworks accident (1 in 600,000)
Asteroid impact (1 in 720,000)
Food poisoning by botulism (1 in 3,000,000)
Shark Attack (1 in 8,000,000)
Mayan "2012" Apocalypse (ZERO... it's a hoax!)
(source: Alan Harris).

Ideas are not set in stone. When exposed to thoughtful people, they morph and adapt into their most potent form.
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« Reply #10 on: December 23, 2012, 04:01:34 pm »

That's asteroids. The picture is less certain for comets, which could appear with only about a years warning and do unavoidable damage.
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« Reply #11 on: December 23, 2012, 04:01:49 pm »

And a 40 % probability - within the 21st century - of a global catastrophe due to nuclear war.
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« Reply #12 on: December 23, 2012, 04:02:45 pm »

"Only 13,000 years ago, the North American megabeasts -- including woolly mammoths, saber-toothed cats, giant sloths -- also had a very bad day. Well, at least a bad millennium. It was so bad that some scientists have mistakenly attributed that mass extinction to a 2 ½ mile-wide comet explosion. That idea has also been debunked by many scientists"

And it has NOT been debunked by many scientists...far from it. The Younger Dryas Boundary hypothesis (which proposes that a cosmic impact took place 12,900 years ago) is very well documented.

---

http://www.ia.ucsb.edu/pa/display.aspx?pkey=2748

"An 18-member international team of researchers that includes James Kennett, professor of earth science at UC Santa Barbara, has discovered melt-glass material in a thin layer of sedimentary rock in Pennsylvania, South Carolina, and Syria. According to the researchers, the material –– which dates back nearly 13,000 years –– was formed at temperatures of 1,700 to 2,200 degrees Celsius (3,100 to 3,600 degrees Fahrenheit), and is the result of a cosmic body impacting Earth."
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« Reply #13 on: December 23, 2012, 04:03:52 pm »

ONGOING CATASTROPHE!

Thousands Remain Displaced From Sandy Without Heat and Power

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« Reply #14 on: December 23, 2012, 04:05:25 pm »

If we need funding to take care of one of these asteroids then all we have to do is tell the right that the money is for a tax cut for the rich and we will get the funding in hours not weeks or years.
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