How well would modern society handle the dinosaur killing meteor if it happened today?

I’m going to make the WAG (wild-assed guess) that turning half the planet into a superheated atmosphere with associated firestorms from a shotgun of impacts is probably not healthy for the other half of the planet either. But a multitude of fragments probably avoids the issue from the CT killer, that ejecta from the initial impact went suborbital and came down all over the globe, even well over the horizon.

Should also add that the Wiki article mentions that sulphur compounds and other crustal debris had chemical effects on the environment (acidification and aerosols creating global winter, for example) that a large number of smaller impacts might not.

The real question would be - is it worthwhile? How much specific impulse could a system like that impart? Current tech for downing missiles simply hopes to inflict severe mechanical failure on the missile, not to completely vaporize and certainly not to just drive it off course. It would have to be a powerful laser to boil off enough of the target to create a jet effect of the material boiling off. Plus, is the target spinning? I presume launching a bunch or a flock of impulse engines (rockets or ion engines) to attempt to push the target off course is more productive, especially if you could simply continuously resupply them with more fuel given enough time.

I cannot do the math myself but again the source cited said that 10 kW lasers could be worthwhile to alter the course of a 100 meter wide asteroid if identified 30 years before impact. We apparently are needing over 6 orders of magnitude more power than that, space based. The current 10 PW laser is 13 orders of magnitude larger. You’d need such space-based (with enough power and cooling), able to maintain focus on its target, and at the smallest possible beam divergence. A reach but not beyond imagining.

Another key issue in space is actio = reactio. If the laser is powerful enough to move an asteroid with a mass of trillions of kilogramms, where and how fast will the laser move?

It doesn’t matter what size animal survived right after the impact. The size of any animal 1 year out, 10 years out, 100 years out matters a lot. We can’t tell if a crocodilian slightly bigger than a housecat managed to survive the initial period but even larger ones may have survived as eggs. Who knows what dinosaurs of what size were still wandering around some remote part of the world trying to survive for how long, they were all gone before long save for the ones that became modern birds.

.

ICBMs are kept on standby because of the perceived deterrence value. (Whether they actually provide the level of assumed deterrence isa debate for another thread; I’m just establishing this in terms of the conventional justification.) In order to prevent a large potential impactor we would need to have many months of lead time, both to get the redirect system into position to intercept the object and because of the limited amount of impulse that could conceivably be applied to it means that we’d need to make a trajectory alteration as far out as possible. Now, obviously having a system capable of launching and deploying an asteroid redirect system would be prudent, but it isn’t as if you’d need to launch it at a moment’s notice; in fact, you’d probably want to run extensive and peer-reviewed studies on the best way to apply impulse to redirect it to prevent future hazards and contingencies for breakup scenarios.

No, absolutely not, although most large asteroids are a consolidation of smaller bodies and preventing them from breaking up is a significant challenge. Although breaking it up into smaller pieces means that more or all of it will “burn up” (vaporize) in the atmosphere, that atmosphere is still a crucial part of our planet and delivering that much energy will still do tremendous damage even if no solid parts of it reach the surface. Furthermore, breaking it up means dozens or hundreds of individual pieces that would then have to be tracked and moved separately rather than redirecting one large mass, and if in a periodic orbit could repeatedly intercept the Earth. The only reason I could see for wanting to do this is if the singular object is too large to shift, but that doesn’t fundamentally change the total impulse requirements, so it remains a problem noentheless.

Here is a concept I have promoted for using nuclear weapons to generate a mediated impulse to redirect a hazardous object without breaking it up. This is obviously not trivial, and the potential for weaponizing this, particularly if it were kept on some kind of standby status, is evident, but it would make sense to develop this capability or something like it as a hedge against a future threat.

Although the SDI program only lasted for a few years, the research and development of very high throughput lasers has gone on for decades without producing something capable of actually destroying an ICBM from hundreds of miles away. And while there is the thermal blooming problem of firing through an atmosphere, inherent divergence and other issues with laser throughput are actually the more problematic issues with making such a system workable.

The laser system cited in the press release you linked to is the centerpiece of a large research facility which is developed for doing nuclear physics research. It is a pulsed laser in no way a system that could ever be developed for shooting large rocks in space for extended periods of time, with pulse durations measured in the hundreds of femtoseconds. Although we may some day be capable of building very high power throughput lasers capable of continuous operation sufficient to disintegrate or provide impulse to very large objects millions of miles away in space as portrayed in science fiction and specious asteroid redirect proposals, that is very far away from current capabilities in directed energy science. I believe @CalMeacham actually works in this field and can provide specific expertise to this proposal but I think he’ll agree that it is not feasible within the foreseeable future, and the fundamental energy requirements to do so would be prohibitive in any case.

“…if life is going to exist in a universe of this size, one thing it cannot not afford to have is a sense of proportion.”

Stranger

What will it take to get observation satellites in place to try to spot these things when they are far away enough to do something about them? There’s not much chance we’ll spend a lot of money on asteroid killer/deflection tech if we can’t even find one to worry about.

Not all that much. We have a current program utilizing ground based observatories for asteroid detection and tracking which JPL has already been studying for a long time but they are obviously limited by the amount of sky they can observe. The WISE satellite [NEOWISE program] was deployed to search for and catalogue minor planets missed by ground surveys (though not potentially hazardous objects in particular) and was revitalized for the (NEOWISE, studying near-Earth asteroids | The Planetary Society) as a proof of concept for a dedicated asteroid hunter. The Planetary Society has long advocated for a follow-on program of observation satellites dedicated to planetary defense:

I once worked on an unsolicited proposal for an interplanetary telemetry and positioning system which as a secondary capability would have hosted small body observatories capable of imaging everything 10 meters and larger within the orbit of the Earth including all Aten, Atira, Amor, Apollo group objects that could pose a hazard. Unfortunately, like most such proposals it went nowhere which is unfortunate because it is a capability needed to expand interplanetary space exploration as well as the benefits for planetary defense.

Stranger

Another approach but one that would require the lead time to get it into place and the ability to autotrack -

Meanwhile at least NASA is working on something for the more common threats! DART. The Double Asteroid Redirection Test.

This video (skip to1:35) says the dino killer hit at almost the perfect spot to do the most damage. They suggest hitting in deep ocean would have been much less damaging globally.

Didn’t watch the vid. But Chicxulub was 15km in diameter. The central oceans are 3 or 4 km deep. Leaving the top of the impactor still in the stratosphere above 90% of teh atmosphere as the bottom is hitting, well, bottom in the central Atlantic or Pacific.

Viewed at the correct scale, the Earth is a very big rock with a very thin wrapper of air and an even thinner coating of slightly lower wet spots called “oceans” here and there. Impactors deeper than the oceans & atmosphere put together are out there.

Comets are the real problem.

We can see asteroids decades, centuries in advance. It is unlikely that there are any 15km asteroids that we are unaware of.

Comets, however, if they are long period, we may not know more than a few months ahead. If they come in at a bad angle, where we are blinded by the sun, we may have even less.

AIUI we also tend to focus what little effort we’re spending looking mostly along the ecliptic. Comets have a lot more freedom to approach from high angles than do other objects.

Oumuamua and brethren would like a word with you.

was discovered Oct. 19, 2017
While originally classified as a comet, observations revealed no signs of cometary activity after it slingshotted past the Sun on Sept. 9, 2017 at a blistering speed of 196,000 miles per hour (87.3 kilometers per second). It was briefly classified as an asteroid until new measurements found it was accelerating slightly, a sign it behaves more like a comet

We didn’t see it until it was headed out. I will grant 2/3km is harder to see than 15km but except for luck we won’t see a 15km interstellar object decades or centuries in advance.

There are a couple of ideas on why that area was so damaging. One says that because the rocks were rich in gypsum the would have released a lot of sulfur. The other says it was because the rocks contained oil-rich sediments that produced a lot of soot when vaporized (however, drilling has not confirmed this).

In contrast, the floor of the deep ocean is made up mostly of basalt, which would not have produced these substances when vaporized. And there are similar-sized craters on the continents that don’t seem to have produced equivalent extinction events.

The damage done by an impactor is basically proportional to its energy. Whether that energy is deposited in atmosphere, water, or rock, and whether it’s all in one spot or spread out, makes very little difference.

Though of course, breaking up an object could mean that some of the fragments miss. You could even try to break an object in half, to use the two halves as reaction mass for each other.

It’s been almost 40 years since I read Carl Sagan’s Cosmos, so I may have this wrong. But one thing that stuck with me is his assertion that the event killed everything above 50 pounds mass. I don’t think modern society would survive something like that.

I suspect the odds of being hit by an big asteroid may be higher than by a big comet or interstellar object - the latter usually get one pass (and we’ve seen most big comets) Haley’s comet is about 11km diameter and by density, appears to be mostly assorted ices. An decent sized Interstellar object with one pass actually impacting earth sometime in the next million years would be a remarkable coincidence. The risk I assume with asteroids is that some might be gravitationally perturbed to put them on an eventual collision course, particularly if the orbital disturbance is regular and progressive. but for those - we should be able to see them coming decades in advance. IIRC we’ve identified some that come too close for comfort already, and the closer they get, the more earth influences their orbit. If we have decades of warning, presumably someone will do something. Presumably…

The main issue with any CT event is the resulting environmental disruption - yes, tiny animals may survive - but what do they eat during a global winter if no plants grow? Considering some advanced animals survived (and plants) presumably there were pockets of life that were relatively only partly scathed? Plants can survive as dormant seeds, but I doubt that assorted reptiles or amphibians could hibernate for years. Perhaps rat-like creatures could live off frozen plant material long enough to wait out an extended winter, or maybe there was a warm enough habitable zone near some geological active areas.

The biggest fallout from chicxulub seems to be the destruction of plant life, leading to starvation down the food chain, but isn’t that a problem that modern humanity could overcome? We have access to artificial light, so we could still produce crops. I mean, I can see devastation at the location of impact, and perhaps a shortage of food that causes social strife, but it’s not like humanity would die out a la the dinosaurs, right?

I’ve heard that the bulk of the deaths came from the worldwide wildfires spawned in the immediate aftermath of the collision, from debris from the impact coming back down. The creatures that survived might have been in ponds, or perhaps on small islands that were sufficiently isolated from the surrounding fires, and chanced not to get hit by any of the debris directly.

Though, yes, those few that survived the immediate calamity might have had a hard time finding food in the subsequent few years of winter.