Apophis to impact earth in 2036?

[Ivan Seeking]

This is probably the third time that I have heard or read conflicting reports on this.

...The group is made up of people who are experts in near-Earth objects, for which they make the acronym NEO. They had a conference in London recently and compared notes on their findings.

The asteroid in question was identified in 2004 and studied in 2005 for its trajectory. At first they were scared enough to believe that it could hit the Earth in 2029. Then they did some more fine-tuning of their computer data and decided that it would come close to the Earth in 2029, but wouldn't be on a possible collision course until 2036.[continued]

http://www.rutlandherald.com/apps/pbcs.dll/article?AID=/20060104/NEWS/601040303/1039

...Yeomans: Right -- you mentioned Apophis, which is an asteroid about 300 meters in size that will get very close to the Earth on April 13, 2029. In fact it will get beneath the geosynchronous satellites -- the same satellites that are probably used to beam your radio signals to your listeners. Certainly television and Earth surveying satellites are at geosynchronous orbits, and this asteroid will get beneath them and become a third magnitude naked-eye object for a period of time. So that's kind of exciting. But -- it won't hit the Earth. [continued]

http://www.Earth'sky.org/shows/astrophysics_interviews.php?id=49241

 

[Pengwuino]

So... call me stupid (don't call me stupid), but why again can't we just send up a couple of nukes to at least move or breakup these things? I don't really see what could be worse then something hitting Earth and whiping out all of mankind...

 

[Ivan Seeking]

Simulations indicate that in many cases we could just make things worse by breaking it up, or it may have too little influence to be of use, but a few people are exploring all sorts of ways to deflect asteroids.

 

[Pengwuino]

Well what would "worse" be? Is the planet going to be destroyed twice as bad? :P

How big does something have to be until anything we do starts having "little to no influence" with current technology?

 

[Ivan Seeking]

Apparently one big object can be a better option than a bunch of little ones - I assume because the latter affects a larger area.

 

[russ_watters]

Well what would "worse" be? Is the planet going to be destroyed twice as bad? :P

Same theory as with nuclear weapons (why we use MIRVs instead of just really really big bombs) - doubling the energy does not double the damage because so much of the energy goes into digging a big hole. Since that area has already been completely destroyed, digging a biger hole there isn't going to destroy it any worse. More objects means smaller craters but far more widespread damage. But of course, a lot depends on where they hit.

Hypothetically, if you had a big asteroid that was going to turn Europe into a big crater, the US would probably be OK - but splitting it in half might cause one half to hit Europe and the other the US - turning both into only slightly smaller craters.

 

[Pengwuino]

Well i was thinking... if the objects are smaller, would friction be able to reduce the pieces sizes more then if it were one huge object..

 

[russ_watters]

Yes, but you'd really have to shatter it. The pieces would need to be a tiny fraction of the initial size. For an impact at 30,000 mph, the atmosphere doesn't take off as much as you may expect.

 

[Janus]

This is probably the third time that I have heard or read conflicting reports on this.
http://www.rutlandherald.com/apps/pbcs.dll/article?AID=/20060104/NEWS/601040303/1039
http://www.Earth'sky.org/shows/astrophysics_interviews.php?id=49241

While Apophis will pass close to the Earth in 2029, There is no chance of collision at this time, but if, during that close approach, it passes through a small window known as the "keyhole" it will be put in an orbit that will cause a collision in 2036.

Now, the keyhole is much smaller target than the Earth so if we needed to deflect Apophis to prevent said collision, our best bet is to deflect it prior to 2029 such that it misses the keyhole.

 

[Chronos]

Predicting asteroid orbits is frightfully complicated. Talk about n-body simulations. The small mass makes it susceptible to the slightlest tugs of other, more massive bodies in the solar system.

As others have noted, blasting it to pieces is not a good solution - unless the pieces are small enough to burn up in the atmosphere. Think of it as a 00 shotgun blast compared to a rifle slug. Deflecting the large mass so it lands in an ocean [or misses the Earth entirely] is a much better bet.

 

[Janus]

Deflecting the large mass so it lands in an ocean [or misses the Earth entirely] is a much better bet.

An ocean strike could be worse than a land strike. A land strike would be localized, an ocean strike could trigger a tsunami that would affect large areas of coastline.

 

[D H]

An ocean strike would be much worse than a land strike. Nearly all of the energy from an ocean strike is converted into water vapor, while a significant portion of the energy from a land strike would be radiated into space. The tsunami from an ocean strike is just a harbinger of the bigger problems that will ensue.

The nuclear option is not so bad so long as the explosion is used to change the asteroid's orbit rather than break it into a lot of little pieces. However, we need to know a lot more regarding the asteroid's composition to determine if the nuclear option is viable. Some asteroids are tight, compact masses. Others are already a conglomerate of little pieces that are loosely held together by the asteroid's weak gravity. Exploding a nuke near a tight, compact mass won't do a whole lot of damage but it will change the orbit. On the other hand, blowing up a dirt ball will disperse the dirt ball, thereby increasing the chances of a collision.

 

[Andre]

How about manoeuvring a satelite to land on it or attach to it and then giving it a good braking with a rocket engine to get it into a much lower orbit around the sun. Then it would never get close to Earth again.

And better do it as soon as possible while we still have the technology and the fossil fuel.

 

[Art]

Here's a new approach NASA are exploring in handling asteroids;

Summary - (Dec 29, 2005) Forget about nuclear weapons, if you need to move a dangerous asteroid, you should use a tractor beam. Think that's just Star Trek science? Think again. A team of NASA astronauts have recently published a paper in the Journal Nature. They're proposing an interesting strategy that would use the gravity of an ion-powered spacecraft parked beside an asteroid to slowly shift it out of a hazardous orbit. Dr. Stanley G. Love is member of the team and speaks to me from his office in Houston.

<snip> We were sort of developing the idea as a generic idea, and fly to anything. However, there's Asteroid 99942 Apophis which is supposed to make a close pass of the Earth I think in 2029. And if that asteroid happens to pass through exactly the right point in space as it goes past the Earth, it has a chance to come back in 7-8 years and hit us, which would be bad. And that asteroid is an excellent target for this kind of a mission. If we can get to it before that first Earth flyby, that would line it up for impact the second time around. And the reason for that is that these flybys warp the path of the asteroid so that a tiny tiny change in the flight direction before the flyby gives a huge change in the flight direction after the flyby. So it's like a bank shot in pool. A little tiny mistake on the first part, after the bounce, the mistake gets multiplied. So you could use a gravitational tractor that wasn't nuclear powered and didn't weight 20 tons. You could use a 1-ton, chemical-propelled gravity tractor to pull this asteroid just slightly off course before that Earth flyby so the asteroid is going no where near us.

http://www.universetoday.com/am/publish/podcast_gravity_tractor_beam.html[/URL]

 

[Vast]

An ocean strike could be worse than a land strike. A land strike would be localized, an ocean strike could trigger a tsunami that would affect large areas of coastline.

NASA initially estimated the energy that Apophis would have released if it impacted Earth…. A more refined later estimate was 870 megatons…. The 1883 eruption of Krakatoa was the equivalent of roughly 200 megatons.

http://en.wikipedia.org/wiki/2004_MN4#Possible_impact_effects"

Over four times the destruction of the Krakatoa eruption! That’s a lot of energy and destruction, but not quite life threatening to mankind. I’m not sure it would make much difference on land or ocean, as the dust would surely effect climate all around the world. Though I would probably still say it would be worse if it impacted the ocean.

 

[WarrenPlatts]

Over four times the destruction of the Krakatoa eruption! That’s a lot of energy and destruction, but not quite life threatening to mankind.

It's only about the size of a single antimatter car bomb. . . .

 

[Chronos]

A tsunami would only affect coastal regions, a land strike would raise a dust cloud that would play h*ll with the atmosphere for years. Earth would recover much more rapidly from an ocean strike.

 

[Spin_Network]

Here's a new approach NASA are exploring in handling asteroids;
http://www.universetoday.com/am/publish/podcast_gravity_tractor_beam.html[/URL][/QUOTE]

I am pretty certain that the best is yet to come?

It will be a "non-destructive" application that will be the best.

Maybe a 'deflection' devise can be implimented, if enough is known about the Asteroids structure and density, a number of low-energy nuclear devises could , in theory be used to induce "shock-wave", non-destructive energy fronts? that cause the Asteroid to stray from its Earthbound course.

If there is a high metallicity content on the asteroid, there are, again "in theory", a good chance that a device can be made to dump a large "electrical-charge" or "magnetic-field" upon the Asteroid, if one can get the knowledge needed at an early stage?

 

[tony873004]

...The small mass makes it susceptible to the slightlest tugs of other, more massive bodies in the solar system...

Would it be more correct to say that the small mass makes it more susceptible to forces such as solar radiation pressure, solar wind, and the Yarkovsky effect? The more massive bodies in the solar system will not tug it harder simply because of its low mass. Due strictly to gravity, it will accelerate the same whether it's a piece of microscopic dust, or a full planet for the same reason that a big rock and a small rock drop to the ground at the same rate.
Regarding blasting it into a million pieces, I don't see why that would be a bad idea unless we did it only a few days before impact. Sure, it would be no better to be blasted with a million small pieces with a combined mass of one big piece. But why would we get blasted by all 1 million pieces? Why would the asteroid fragment into a million pieces and then travel through space like science fiction asteroid field. The pieces will not have enough combined gravity to pull themselves together again into a single asteroid. So they will continue to spread apart. Even if the individual pieces were traveling 1 meter per second with respect to each other, in only 150 days, the average spacing between them would exceed 1 Earth diameter. Earth may just simply cruise through the open space in the diffuse debris belt without getting hit at all, or just getting hit by a few pieces of the original million.

 

[Ivan Seeking]

From an previous report. I still don't know the proper time line on all of this or the current odds that it will strike. I assume that a couple of news reports were inaccurate, and also that a few astronomers who commented on this didn't know about the potential for a strike in 2036 and were speaking to the 2029 encounter.

NASA provided a formal response to the B612 Foundation’s June communiqué via an October 12 letter from Mary Cleave, Associate Administrator for Science Mission Directorate.

That NASA reply came with an appended detailed analysis by Steven Chesley of NASA’S NEO Program Office at the Jet Propulsion Laboratory (JPL) in Pasadena, California. The study by Chesley dug into Apophis’ orbit, under varying conditions, and contained other items pertaining to the space agency’s findings about the Apophis matter.

“The key conclusion to be taken from this analysis,” Cleave explained in the letter, “is that aggressive (i.e., more expensive) action can reasonably be delayed until after the 2013 observing opportunity. For Apophis, the 16 years available after 2013 are sufficient to recognize and respond to any hazard that still exists after that time.”

Cleave noted in the letter that while Apophis “is an object whose motion we will continue to monitor closely in the coming years, we conclude a space mission to this object based solely on any perceived collision hazard is not warranted at this time.”

Not ruled out by Cleave, however, is the prospect of Discovery-class, low-cost missions sent to Apophis, “based on purely scientific arguments,” she said.

“Indeed, the asteroid’s orbit is particularly attractive for spacecraft rendezvous, and the extraordinary close encounter in April 2029 provides a unique opportunity to investigate a number of scientific NEO issues,” Cleave explained in the letter. [continued]

http://www.space.com/news/051103_asteroid_apophis.html

 

[tony873004]

"For Apophis, the 16 years available after 2013 are sufficient to recognize and respond to any hazard that still exists after that time.”

Is this the part you were referring to? Perhaps its not referring to a 2029 impact, but simply that if a 2036 impact were confirmed after the 2013 radar observation, we would have until 2029 to deflect this asteroid with minimal effort. Changing it by only a small amount prior to the 2029 flyby will result in large changes by 2036, but a much larger effort would have to be employed to deflect it after its 2029 Earth flyby.

 

[Andre]

But then again, would we still be able to do such things in 2029? What if there is no more fuel/technology/prosperity?

 

[Math Is Hard]

Back in the news
http://abcnews.go.com/Technology/wireStory?id=2886807

Feb 19, 2007 — SAN FRANCISCO (Reuters) - An asteroid may come uncomfortably close to Earth in 2036 and the United Nations should assume responsibility for a space mission to deflect it, a group of astronauts, engineers and scientists said on Saturday.

 

[DaveC426913]

Here's a new approach NASA are exploring in handling asteroids;
Summary - (Dec 29, 2005) Forget about nuclear weapons, if you need to move a dangerous asteroid, you should use a tractor beam. Think that's just Star Trek science? Think again. A team of NASA astronauts have recently published a paper in the Journal Nature. They're proposing an interesting strategy that would use the gravity of an ion-powered spacecraft parked beside an asteroid to slowly shift it out of a hazardous orbit. Dr. Stanley G. Love is member of the team and speaks to me from his office in Houston.

Ah yes. Tractor beam = ... gravity. Star Trek-watching journalists have enriched our lives once again...

 

[TripleS]

But then again, would we still be able to do such things in 2029? What if there is no more fuel/technology/prosperity?

what if there is no-one to hit..after all if there is an apocolyptic war, there may not be enough man power to design the large effort required to move the asteroid. The world will always postpone anything and is costs a lot of money for something that may never eventuate.

 

[MadScientist 1000]

870mT? That's not that bad as some might expect. But what other realistic options do we have that can be built with today's tech?

what if there is no-one to hit..after all if there is an apocolyptic war before, there may not be enough man power to design the large effort required to move the asteroid. The world will always postpone anything and is costs a lot of money for something that may never eventuate.

That would certainly not be a good thing, but maybe we will pull ourselves together and stop fighting if we realize in a little more than a decade there will be nothing left to fight over... Hopefully...

 

[TripleS]

For the mere chance that the world will be hit by an asteroid, they will stop an entire war..

it'll be more likely that after the war has finished, and a year before (or even later) when they are absolutely sure that it will hit earth..they might actually do something..and by then it would too late

look at global warming for example...we know that it is happening yet we are not doing much about it...

 

[joema]

870mT? That's not that bad as some might expect. But what other realistic options do we have that can be built with today's tech?...

NASA currently estimates about 400 megatons for an Apophis impact: http://neo.jpl.nasa.gov/risk/a99942.html

At first that sounds big, considering the largest nuclear bomb ever detonated (Soviet Tsar Bomba) was about 50 megatons: http://en.wikipedia.org/wiki/Tsar_bomba

However primary damage is blast, which at a given distance increases as the cube root of quotient of two comparative megatonages. 50 MT won't kill everybody within 50 km, as the aircraft which dropped the 50 MT Tsar Bomba was only 45 km away when it detonated.

Had the bomb instead been 400 MT (current Apophis estimate), the destructive force at 50 km would be (400 / 50)^.33 = approx 2x as great.

Unless Apophis fell directly on a city it wouldn't kill huge numbers of people. Since most of the Earth is covered with oceans, there's a good chance it wouldn't kill many people, even if nothing was done. You wouldn't want to rely on that, but those are the probabilities. Many large nuclear bombs have been detonated at sea -- they don't cause huge tidal waves that destroy cities many miles away.

If an object on collision with Earth is detected in plenty of time -- say several years out -- there are various options. The "gravity tractor" is a nice gentle approach, achievable with current technology:
(html):http://arxiv.org/pdf/physics/0608157
(200kb pdf): http://arxiv.org/pdf/physics/0608157

The main drawback is its deflection ability is limited, which means early detection is required, especially for more massive objects.

If that didn't work or the object wasn't discovered in time, most ICBMs can reach escape velocity with a pared-down payload. A precision stand-off nuclear detonation would vaporize a thin layer of surface material, nudging the object off course. There is no blast wave in space, like in Earth's atmosphere, so the object wouldn't be fragmented or shattered.

The gravity tractor approach is preferable, but the nuclear approach is definitely available and could achieve much greater deflections, and requires much less prep time. You'd have to develop a redundant radar proximity fuze, but those have existed since WWII. Also needed would be high precision deep space guidance -- standard inertial nav isn't good enough. But those technologies exist and could probably be retrofitted within weeks.

In reality if a collision was highly likely you wouldn't rely on any single approach -- just too much at stake. You'd probably have several redundant gravity tractor launches, anyone of which could deflect the object. As a contingency against those failing, other options would be developed in parallel, including modified ICBMs.

 

[Sojourner01]

Could a laser, in theory, impart enough power to an object the size of an asteroid to change its course?

Consider that the US military is looking at breaking the 100kW barrier for a robust, portable laser system any time soon, probably within the next couple of years.

 

[carlos_dfc]

There's a handy 'Impact effects' calculator here...
http://www.lpl.arizona.edu/impacteffects/

I just ran a couple of scenarios through it - based on an asteroid the size of Apophis (roughly 300m across) striking at 17km/s (typical asteroid impact speed) - coming in at 60 degrees, and with an observer's viewpoint of 100 miles away.

Deep water strike - 1km deep (in open sea)
Observer (at 100 miles) would see a fireball, and feel thermal radiation about 0.7 times bright sunlight.
Tremors of 5.7 on the richter scale - 26mph winds - and a blast sound about as loud as heavy traffic. Ejecta mostly fine dust, with bigger pieces averaging 4cm.

On land - sedimantary rock.
Crater 3.3 miles across - fireball almost a mile across.
From 100miles you'd see the fireball as roughly twice the size of the Sun, and 0.7 times the intensity.
Tremors of 6.7 - with average ejecte fragments, 9mm

Those were based on a dense rock structure to the asteroid - for a mostly iron structure - tremors slightly bigger - crater, ejecta etc roughly double in size.

Obviously, it would cause localised devastation - but no great shakes on a global scale.

 

[joema]

Could a laser, in theory, impart enough power to an object the size of an asteroid to change its course?...

No, the military lasers fire for only a few seconds at most. They just can't deliver enough total energy to make a difference.

One of the most powerful military laser programs is the 1 megawatt Boeing Airborne Laser. It supposedly will be able to fire about 20 rounds of (maybe) several seconds each. If we take 3 sec/round as typical, that's 60 sec total firing time. Total energy emitted would be about 60 million joules, but you'd lose energy from atmospheric absorption, even if adaptive optics maintained focus.

Due to beam divergence, it would also only be useful at very close ranges. The beam divergence of a 1.35 micron, 1.5 meter dia COIL laser is about 1.15 microradians. At distances of more than a few thousand km, the beam would be much wider than the asteroid.

Even if 100% of energy was delivered, 60 megajoules is roughly the energy of 1/2 gallon of gasoline. It's just not enough, when the object weighs 2.1E10 kg.

You can hypothesize much larger ground-based lasers, but in general, they aren't an efficient way to deliver energy in quantities needed for asteroid deflection.

 

[MadScientist 1000]

http://www.lpl.arizona.edu/impacteffects/
http://en.wikipedia.org/wiki/99942_Apophis

The site is a calculator for the effects of an asteroid hitting us. Just find data on Apophis and plug it in.

Update:

I did a bit of the work here, and found some data. Credit goes to the site and wikipedia.

Impact Effects
Robert Marcus, H. Jay Melosh, and Gareth Collins

Please note: the results below are estimates based on current (limited) understanding of the impact process and come with large uncertainties; they should be used with caution, particularly in the case of peculiar input parameters. All values are given to three significant figures but this does not reflect the precision of the estimate. For more information about the uncertainty associated with our calculations and a full discussion of this program, please refer to this article

Your Inputs:
Distance from Impact: 80.50 km = 49.99 miles
Projectile Diameter: 250.00 m = 820.00 ft = 0.16 miles
Projectile Density: 1500 kg/m3
Impact Velocity: 30.73 km/s = 19.08 miles/s
Impact Angle: 45 degrees
Target Density: 2750 kg/m3
Target Type: Crystalline Rock

Energy:
Energy before atmospheric entry: 5.79 x 1018 Joules = 1.38 x 10^3 MegaTons TNT
The average interval between impacts of this size somewhere on Earth during the last 4 billion years is 2.9 x 104years

Atmospheric Entry:
The projectile begins to breakup at an altitude of 82000 meters = 269000 ft
The projectile reaches the ground in a broken condition. The mass of projectile strikes the surface at velocity 23 km/s = 14.3 miles/s
The impact energy is 3.25 x 1018 Joules = 7.77 x 10^2MegaTons.
The broken projectile fragments strike the ground in an ellipse of dimension 1.21 km by 0.859 km

Major Global Changes:
The Earth is not strongly disturbed by the impact and loses negligible mass.
The impact does not make a noticeable change in the Earth's rotation period or the tilt of its axis.
The impact does not shift the Earth's orbit noticeably.

Crater Dimensions:
What does this mean? Crater shape is normal in spite of atmospheric crushing; fragments are not significantly dispersed.

Transient Crater Diameter: 3.15 km = 1.96 miles
Transient Crater Depth: 1.12 km = 0.692 miles

Final Crater Diameter: 3.68 km = 2.29 miles
Final Crater Depth: 0.438 km = 0.272 miles

The crater formed is a complex crater.
The volume of the target melted or vaporized is 0.0205 km^3 = 0.00491 miles3
Roughly half the melt remains in the crater

Thermal Radiation:
What does this mean? Time for maximum radiation: 0.129 seconds after impact

Visible fireball radius: 2.46 km = 1.52 miles
The fireball appears 6.93 times larger than the sun
Thermal Exposure: 1.88 x 105 Joules/m2
Duration of Irradiation: 38.5 seconds
Radiant flux (relative to the sun): 4.87 Seismic Effects:
What does this mean? The major seismic shaking will arrive at approximately 16.1 seconds.
Richter Scale Magnitude: 6.5
Mercalli Scale Intensity at a distance of 80.5 km:

IV. Felt indoors by many, outdoors by few during the day. At night, some awakened. Dishes, windows, doors disturbed; walls make cracking sound. Sensation like heavy truck striking building. Standing motor cars rocked noticeably.

V. Felt by nearly everyone; many awakened. Some dishes, windows broken. Unstable objects overturned. Pendulum clocks may stop. Ejecta:
What does this mean? The ejecta will arrive approximately 129 seconds after the impact.
At your position the ejecta arrives in scattered fragments
Average Ejecta Thickness: 1.69 mm = 0.0666 inches
Mean Fragment Diameter: 4.01 cm = 1.58 inches Air Blast:
What does this mean? The air blast will arrive at approximately 244 seconds.
Peak Overpressure: 10600 Pa = 0.106 bars = 1.51 psi
Max wind velocity: 24 m/s = 53.7 mph
Sound Intensity: 81 dB (Loud as heavy traffic)
Damage Description: Glass windows will shatter.
Tell me more...

Click here for a pdf document that details the observations, assumptions, and equations upon which this program is based. It describes our approach to quantifying the important impact processes that might affect the people, buildings, and landscape in the vicinity of an impact event and discusses the uncertainty in our predictions. The processes included are: atmospheric entry, impact crater formation, fireball expansion and thermal radiation, ejecta deposition, seismic shaking, and the propagation of the atmospheric blast wave.

Earth Impact Effects Program Copyright 2004, Robert Marcus, H.J. Melosh, and G.S. Collins
These results come with ABSOLUTELY NO WARRANTY

 

[bassplayer142]

I just started reading this thread and wow is all I can say. Why couldn't we send a ton of nukes at it when it is really far away. Even if it exploded into a few pieces of it will most likely not be headed to Earth after that.

 

[joema]

...Just find data on Apophis and plug it in...

Based on this NASA web site:http://neo.jpl.nasa.gov/risk/a99942.html, the impact velocity would be about 12.59 km/s. Since kinetic energy increases with square of velocity, this would reduce the energy to roughly 400 megatons.

 

[DaveC426913]

I did a bit of the work here, and found some data. Credit goes to the site and wikipedia.

Thought I'd separate the wheat from the chaff:

An asteroid 250m in diameter, traveling at 30km/s enters the atmosphere at a 45 degree angle. It begins fragmenting at 75km altitude creating an impact area roughly 1 km in diameter. The pieces strike at about 23km/s. In 1/8 second a fireball is formed 2.5km in radius


80km away:
0s: fireball appears, 7 times larger than the sun.
16s: quake arrives of Mag 6.5 (shakes dishes, topples objects, sensation like a truck has hit building)
38s: fireball fades
2m10s: scattered ejecta arrive (1 inch fragments)
6m: air blast (75km/h, sound as loud as heavy traffic, shatters windows)