Asteroids: not a threat to humankind?

[orionrider]

Fact one: Thanks to WISE and other detection means, the sky survey is almost complete: there is a very low probability that an asteroid large enough to cause a global event will impact the Earth in the next century.

Fact two: Space technology is advancing fast enough that humankind will probably develop the capability to alter the orbit of a potential impactor in the next century.

Fact three: Detection and early warning will soon improve to the point that we get at least a century to prepare for a probable impact. This means that less dramatic measures will be required to slowly alter the course of a killer rock, like changing the albedo or using a gravitational tug.

Does this mean humankind is immune from global asteroid threats :?:

 

[MeteorWayne]

Fact one: Thanks to WISE and other detection means, the sky survey is almost complete: there is a very low probability that an asteroid large enough to cause a global event will impact the Earth in the next century.

Not a fact. In part. The sky survey is nowhere near complete, however there is a "
very low probability that an asteroid large enough to cause a global event will impact the Earth in the next century"

Fact two: Space technology is advancing fast enough that humankind will probably develop the capability to alter the orbit of a potential impactor in the next century.

If we decide to do that, yes.

Fact three: Detection and early warning will soon improve to the point that we get at least a century to prepare for a probable impact. This means that less dramatic measures will be required to slowly alter the course of a killer rock, like changing the albedo or using a gravitational tug.[/quote]

Depends on how you define soon. There are always surprises that can pop up, just look at the sizes of onjects that show up on the JPL Sentry risk page. Sure the risks are low, but we still discover km sized objects with some risk.

Does this mean humankind is immune from global asteroid threats :?:

Immune? No. Unlikely for the next century? yes.

That isn't the biggest risk anyway; that would be an Oort cloud comet with 2 months warning.

 

[orionrider]

How likely is an Oort cloud comet? Returning comets disturbed by Jupiter would be more frequent, but provide sufficient reaction time.

Unless we all emigrate to the Jovian suburbs, I believe the probability of humankind being wiped by a rogue comet or asteroid is small enough to be insignificant compared to other dangers.

 

[raptorborealis]

We need to separate two concepts,

A comet, asteroid hitting the Earth and:
Mankind being wiped out by such an event.

As a geologist I don't know of any extraterrestrial event in the last 500 million years, that if it happened today, would have wiped out mankind. Been 'really' bad...yes. Decimated our numbers...yes. But nothing that would wipe out man from all the geography and ecosystems that we live in...Cetainly one like the Chixiclub Cretaceous event 65 million years ago wouldn't have even come close to doing it.

We are quite versatile, adaptive and have technology. If 99.99 of humans die...it still leaves millions of humans. Many more than were around than ten thousand years ago...or a hundred thousand years ago.

It might not be a bad idea to have a system in place, if reasonable cost and practical, that helps save a few hundred millon people but don't worry about 'saving mankind'.

 

[MeteorWayne]

How likely is an Oort cloud comet? Returning comets disturbed by Jupiter would be more frequent, but provide sufficient reaction time.

As I said, the biggest threat is a new Oort cloud comet, because we would have no useful time to react, nor even with the best planning, any possible action.

A JFC is pretty much in the same orbit as an asteroid, so would be unlikely to sneak up on us. Not impossible, but unlikely.

 

[csmyth3025]

While mankind may not be in danger of being obliterated by an undetected space object, we should keep in mind that there is only an organized search for objects about 1 km and larger by (US) government mandate according to Wikipedia.

As I understand it, the Barringer Crater (Meteor Crater) in Arizona is thought to have been caused by the impact of a nickle-iron meteorite about 50 meters in diameter and the Tunguska event is thought to have been caused by the air burst of a meteoroid or comet "a few tens of meters across" that yielded an explosion in the range of 10-15 megatons of TNT.

These "small" objects may not wipe out mankind, but they sure could wreck a city if they fell in the right spot. What are the chances of someting this size "sneaking up" on us unnoticed or with very little warning?

Chris

 

[MeteorWayne]

Actually, many objects are being detected by the current surveys. Some are as small as 6 meters. Yet, the rate of detections of PHA's (Potentially hazardous asteroids) has leveled off even as the surveys have increased in sensitivity.

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

Looking in detail, in the first half of 2010, 406 NEA's were discovered. Here in the second half of 2010 through Aug 23 only 60....that projects to about 130 for the full half year. That's about a 2/3 decrease.

For those that have been here for a while, look at how long it's been since we've had a high risk asteroid we've tracked in SS&A:
viewtopic.php?f=12&t=24327
(That was in May, 3 months ago)
or a close approach in this thread:
viewtopic.php?f=12&t=4613
And that was for a 6-13 m asteroid.

The current highest risk newly discovered asteroid is 2010 PR66 with a Palermo Scale of only -5.42 for one impact in 2107.

Now of course, we could always see a new one tomorrow, but I've noticed a definate slowdown, despite the increasing sensitivity and coverage of the current projects.

I have a feeling our coverage is already better than we think.

 

[orionrider]

It will not take long before we have mapped nearly all substantial geocruiser rocks in this system.
Also the increase in processing power and better digital sensors will make orbital models more accurate, leading to increasingly accurate predictions... and buy us more time to react.

That leaves only the 'rogue' comets or asteroids. A few month warning is not enough, whatever the technological level. It takes decades to deflect a kilometer-sized object. However, I feel that the risk is small enough that we can consider that the Earth is immune from large impacts as long as Mankind maintains it's technological level and development.

 

[EarthlingX]

So what happens if two asteroids collide, and some of the resulting rubble heads our way ? This is rather probable scenario for the demise of dinosaurs.

news.discovery.com : No, Seriously, What Killed the Dinosaurs?

We use a lot of hi-tech to get to resources which we need to run our planetary civilization, and if we got hit hard enough to be pushed back, i very much doubt in easy recovery. You don't need much for people to revert to much less civilized behaviour than you are used to - just switch off electricity.

Anyway, i think we are most likely our biggest danger in the short term, and i consider Hawking to be an optimist.
edition.cnn.com : Hawking: If we survive the next 200 years, we should be OK

This might also give you some food for thought :

http://www.popularmechanics.com : Top 5 Ways the Universe Could Wipe Out Humankind


www.planetary.org : The Potential to Destroy Civilization – Now on YouTube

Aug. 29, 2010 | 09:58 PDT | 16:58 UTC

by Charlene Anderson

Visualization can help the brain comprehend what words and numbers can struggle to covey. There's a YouTube video posted by "szyzyg" making the rounds right now that drives that point home. In the last few decades, our discoveries of these space rocks has increased fantastically – but words and charts just don't convey how much we've done in very little time.

The video simulation begins in 1980, the same year the Planetary Society was founded. At that time, asteroids were considered mere debris left over from the solar system's formation — worthless junk unworthy of much study. But the Planetary Society felt differently. Here's how I phrased our take on the subject in the January/February 2010 Planetary Report:

[youtube]http://www.youtube.com/watch?v=S_d-gs0WoUw[/youtube]

 

[orionrider]

So what happens if two asteroids collide, and some of the resulting rubble heads our way ?

I don't think this is likely on a short time frame. There are not many asteroids cruising in the vicinity of Earth. Any collision between some other large asteroids (eg: in the asteroid belt) would not bring kilometer-sized debris straight to Earth, the delta-vee and momentum would be too large for that.

 

[MeteorWayne]

And asteroid collisions are exceeding rare, only a few are suggested by the asteroid families created in the last billion years.

 

[MeteorWayne]

Did a rough count of known main belt asteroids...

Number... Year
10,000 1981
15K 1990
20K 1993
30K 1997
40K 1998
100K 2000
200K 2002
300K 2005
400K 2007
500K 2010

Yes, the current count is over a half million main belt asteroids, spread over a VERY large volume.

 

[3488]

Yes the main Asteroid Belt occupies a region between 2.05 AU to 3.2 AU from the Sun. The Earth is not at any immediate threat from any of the permanent members that stay within these limits.

NEAs are a potential threat particularly the Earth Crossing Apollo type. Sooner or later Earth IS going to get hit again by one of these.

Also I think the biggest threat of all are from long period comets, a potential previously unknown Earth hitter may be found coming in crossing the orbit of Jupiter, we would have less than 18 months from such a body.

Think of the short period of time it was from the discovery of comets Hale Bopp & Hyakutake, to passing through the inner solar system, particularly Hyakutake discoivered on Wednesday 31st January 1996, passing only 15 million KM from Earth on: Monday 25th March 1996, less than TWO MONTHS after discovery.

Those who think asteroids & comets pose no threat are sticking their heads in the sand. Earth has plenty of impact craters & other impact related scars, & one recent find suggests that the KT boundary impact (part of the cause of the extinction of approx 70% of living things 65 MYA, the dinosaurs being the most famous casualties) was in fact a double whammy, one long known at Chicxulub in Mexico & now possibly a second site in the Ukraine, the 24 KM wide Boltysh Crater formed at the same time.

Andrew Brown.

 

[orionrider]

Hi Andrew, always a pleasure to read your posts

I'm not saying there will be no threat, just that when it happens Mankind will either be already gone (self-destruction or natural disasters), or able to do something about it.
Of course an 'out of the blue' comet like the ones striking Jupiter these days would be quite a challenge. There is nothing one can do in just 2 month, not with foreseeable technology. But what is the math for that happening in the next millennium? Very close to zero I think. And after that, who knows? In 3024, maybe the UN will have a Jupiter outpost loaded with antimatter torpedoes to annihilate any threat to our 'home planet'... :lol: