Comet landing

no one seems to be mentioning that this confirms we can intercept comets that might be on a collision course with Earth.

what to do after interception is debatable. To make the comet accelerate or decelerate a few miles per hour works if some time allows.

there seems to be a consensus that blowing it up would make things worse by just breaking it into more pieces.

the big concern is that a comet on a collision course could appear suddenly, with no time for a reaction. I'm not sure why this is.

Quote: odiousgambit

the big concern is that a comet on a collision course could appear suddenly, with no time for a reaction. I'm not sure why this is.

I believe the spectacular rock from space in Russia in the last couple years was untracked. Not a comet, but a little worse luck than that and you get some serious damage.

Quote: odiousgambit

...the big concern is that a comet on a collision course could appear suddenly, with no time for a reaction. I'm not sure why this is.

The sky is a big place. We don't have eyes everywhere, and even where we do look, we don't see very far.

I think TV shows and movies like, "Star Trek", "Armageddon" or "Deep Impact" or even, "The Fifth Element", or "Starship Troopers" encourage the general public to believe that man-made technology has the ability to alter the course of these massive objects.

Today, practically, we could not do it. While we could navigate an object the size of a small car there, it would take many times that mass to change the course of an, "extinction" sized object.

Also, who's to say that changing the course of even a "city killer" sized object doesn't create a bigger problem when it circles back to the edge of the solar system in a generation, strikes a previously benign massive object out there and sets in in motion on a collision course with the Earth? Maybe were are better off taking the hit.

Quote: Ayecarumba

Today, practically, we could not do it.

It depends. The situation is that the Earth is a tiny target, but that tiny target has a gravitational pull.

Sometimes you see that some object is on a path that takes it uncomfortably near earth 15 yrs from now or so; let's say 3 yrs for the argument something needs to be done. Increasing or decreasing the speed of that latter object 1 mph knocks it off course 26280 miles. I'd like to think the recent landing shows we could intercept that object and alter the speed several mph.

One problem is that objects that get attracted tend to get into elliptical orbits with decreasing radius and eventual collision course. The principal is the same with the WW2 errant circling torpedo problem and submarines. Something going in a circle tends to return to its previous coordinates by definition.

I think that means you need to do a good job of altering course or the problem comes back [g]

An appearing comet on a collision course that gives little time ... those who study this seem to just dread the scenario and have no solution.

Quote: Ayecarumba

Today, practically, we could not do it. While we could navigate an object the size of a small car there, it would take many times that mass to change the course of an, "extinction" sized object.

No. there are many, many types of nukes much less massive than a small car.

Of course:

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Also, who's to say that changing the course of even a "city killer" sized object doesn't create a bigger problem when it circles back to the edge of the solar system in a generation, strikes a previously benign massive object out there and sets in in motion on a collision course with the Earth? Maybe were are better off taking the hit.

One figures in a generation, the technology will be better.

But if your only choice now is to nuke the intruder, then that might be worse. We could merely break it up, resulting in multiple strikes.

Getting to an object, and exerting enough force on it to change its trajectory are very different things. While we could get there, could we change its path enough (while not making the problem worse) to save our planet? Not today.

When the Shoemaker-Levy 9 comet hit Jupiter in 1994, we had only known about it for 19 months. The comet was estimated to be 5 km in diameter before it broke into 20+ smaller pieces that struck the planet with a total force way in excess of our entire nuclear arsenal. If that same object were headed for Earth in 19 months, we could not do a thing about it.

Interestingly, it is estimated that a very large strike occurs on Earth every 130 million years. The last being the one that wiped out the dinosaurs 65 million years ago. So, we've got 64,000,900 years to get something ready for launch.

Quote: Ayecarumba

If that same object were headed for Earth in 19 months, we could not do a thing about it.

One way we've penetrated deep bunkers is to follow missile after missile into the same hole. I am not sure whether this would improve our chances if we could get one or more nukes deep inside.

Unless these things are granite to the middle, we should be able to penetrate deeper than firing on bunkers on Earth which are reinforced steel and concrete.

If perhaps they are structurally weak, that would help also.

Quote: Ayecarumba

Getting to an object, and exerting enough force on it to change its trajectory are very different things. While we could get there, could we change its path enough (while not making the problem worse) to save our planet? Not today.

It depends on the size, mass and composition.

Ideally you'd want something like a mass driver or a propulsion system to alter the object's trajectory. Right now we could only detonate a nuke near it (not on it), and hope the shockwave will deflect it enough and won't tear it to pieces.

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If that same object were headed for Earth in 19 months, we could not do a thing about it.

We could certainly lob a few nuke-tipped probes, perhaps catching it a few weeks away yet. Say 10 weeks if we hurry, there are no major foul-ups, and Congress doesn't pass an emergency law forbidding the use of nukes to save our lives. Whether that would be enough for a Shoemaker-Levy, I've no idea.

Apparently comets break up pretty easily, a problem.

Shoemaker-Levy broke up due to gravitational pull alone, and that is also the theory to explain the chain of craters shown below on Ganymede, a moon of Jupiter.

NASA recently published an article summarizing almost 10 years of fireball tracking data. It shows that fireballs are pretty much randomly distributed across the globe.

The accompanying article also mentions that there is a program to land people on an asteroid with the intention of study, but also to attempt to deflect its path.