NASA boosts impact risk from 'potentially hazardous' asteroid Bennu | Hacker News Reader

NASA boosts impact risk from 'potentially hazardous' asteroid Bennu

news.yahoo.com

34 pointsgraderjs39 comments

For anyone alarmed by this headline - a main conclusion is that there is a possibility of this asteroid being on course to hit earth in the year 2182 or later.

it's been upgraded from 1 in 2700 to 1 in 1750 chance. 0.037% to 0.057%

As I read the headline I went right to the comments to see your comment. Thanks HN for such a nice service and community.

For anyone else wondering whether the "keyhole" term was made up for this or not, no: https://en.m.wikipedia.org/wiki/Gravitational_keyhole

What would we do if an asteroid was on a collision course? Nuke it? Can ICBMs even go to into space?

Redirect it. Double Asteroid Redirection Test mission is going to test soon if this would work in practice:

https://en.m.wikipedia.org/wiki/Double_Asteroid_Redirection_...

The Daily Tribune: "thank the heavens! Earth saved by Wikipedia article"

https://www.nasa.gov/planetarydefense/dart linked from the Wikipedia article

Thanks that's interesting. The article says 0.5mm/s of change is enough to miss the earth, but how much time ahead do we need to find the asteroid? (Assuming we launch the day we find the asteroid, which is politically-wise unlikely but well)

So with an end-stage interaction where you're not considering keyhole effects, you very roughly you need to accumulate an Earth diameter of position change. So Earth diameter is ~13000km, so that works out 26 billion seconds or 825 years.

So in real terms, we'd probably wanna do a but more delta V than that. At 1cm/s, you're down to 41 years for example.

Doesn't this assume the asteroid is dead center targeting earth?

Good point! Assuming that the asteroid sees Earth as a disk that it can hit anywhere uniformly at random and also that I can still do calculus in my head, looks like the expected radius away from the circumference is only 1/3 R?

I’ve got no experience with this stuff. Is it possible to model asteroid redirection in KSP or something similar?

One oddball idea I wonder about is turning suitable asteroids into something like an O’Neil cylinder. They offer lots of mass that you don’t need to haul up and could be resourceful. Seems the mass would help with radiation hazards. Gravity could be simulated by spinning them through traditional means. I’m talking about hollowing them out.

>Is it possible to model asteroid redirection in KSP or something similar?

Yes, you can do it in KSP.

There is even a KSP tutorial for asteroid redirection. Stock game is designed with task in mind.

We can only hope that said asteroid isn't too big and evacuate the area of impact. We can't do anything to prevent it. ICBMs can't even target something in space, and even if we blow the asteroid with one the same mass would still be flying towards earth as a shrapnel. Theoretically we can try shooting it with a laser to evaporate part of it creating thrust to divert it, but we don't have lasers that powerful and probably wouldn't. This is uncomfortable truth - we are completely defenseless against asteroids.

Trivialize the threat publicly, buy/sell off all relevant stocks, then announce threat is worse than anticipated.

Deny again that asteroid is a threat. Redraw a different course in red sharpie over the actual trajectory showing a path missing earth.

Discredit astronomy, discredit nasa, discredit physicists like there's no tomorrow.

Only if they were making money off the asteroid. There’d be more money to make in redirecting it. Especially if we’re talking 150+ years from now with much better space capacities.

This summarizes one possible scenario. https://twitter.com/mycoliza/status/1417539271192309761

> The Torino scale is a method for categorizing the impact hazard associated with near-Earth objects (NEOs) [...]

> # Objects with non-zero Torino ratings

> Currently non-zero: none

https://en.wikipedia.org/wiki/Torino_scale#Objects_with_non-...

So, unless I missed it in there, how big of a crater is this gonna make?

https://impact.ese.ic.ac.uk/ImpactEarth/ImpactEffects/

It'd be a pretty exciting day for anyone within 100km or so of the impact site.

https://impact.ese.ic.ac.uk/ImpactEarth/cgi-bin/crater.cgi?d...

For a water impact, probably a high surf day for an even larger region.

Based on the calculator below, a final crater diameter of 7.39 km ( = 4.59 miles ), and final crater depth of 540 meters ( = 1770 feet ).

I've run estimates of effects for selected distances from 1km to 1,000 km from impact. You'd probaby want to be at least 50 km minimum from ground zero. Strutural damage would be severe, though humans could survive There'd be substantial blast effects to 200 km, as well as ejecta.

Nearer than 50 km, thermal and blast effects, as well as ejecta, would all likely be lethal.

https://impact.ese.ic.ac.uk/ImpactEarth/cgi-bin/crater.cgi?d...

Since you seem like you've the answer for this : what would it look like if it hit the ocean (both off a coast, in shallow water before a drop-off, and maybe way out in the middle of nowhere)? What if it hit Antarctica or somewhere on the north pole? Could it severely impact our ice reserves?

I'm mostly just parroting what the impact calculator says.

There's no estimation of tsunami impacts, though I'm pretty sure that if the asteroid did strike open water, there would be a large tsunami within at least some tens of kilometers. Note that for massive seismic tsunamis you're looking at vertical continental plate displacements of multiple meters across tens, hundreds, or thousands of kilometers, representing vastly greater energies than this impactor. An asteroid is a point displacement that would dissipate rapidly (square of distance, so that doubling distance reduces intensity by a factor of four), and comparatively small energies.

The 2014 Indian Ocean earthquake and tsunami is estimated at about 26 MT equivalent, ten times greater than Bennu. It invovled a linear disruption along ~1,600 km (1,000 mi) of tectonic plate, of "several meters". Think of the difference between throwing a stone into water (meteor) and moving a board back and forth (tectonic plate).

https://en.wikipedia.org/wiki/2004_Indian_Ocean_earthquake_a...

You're looking at a similar situation for an ice impact. The latent heat of fusion of water is high, and the latent heat of vaporisation even higher. Paradoxically, the localised heating converting ice to steam at the impact point reduces the total melting effect.

If the impact were at a critical point that would dislodge an attached ice shelf, there might be a widespread effect, but that's equivalent to placing explosives at a critical weak point of a structure.

The direct heating received is equivalent to that recieved by sunlight falling over a period of 8 hours on a 370,000 km^2 area. That's somewhat less than the size of California. The total area of Antarctica is closer to 14 million km^2.

It's a lot of energy, yes, but on the grand scheme of global warming, a small drop in the bucket.

The energy is enough to melt 31.7 million tonnes (31.7 km^3) of ice, or to vapourise 4.7 millon tonnes (4.7 km^3) of water. (Note that you'd have to first melt and raise the temperature of that water.) A crater 1km deep and 31.7 km in area would have a radius of about 2.25 km. So yes, you'd punch a good-sized hole in the ice, but the net impact is small relative to Antarctica.

Put another way, a large electrical generating plant (2 GW output) releases as much energy as the Hiroshima bomb did (15 kilotons TNT) ... in 9 hours. Both quantities and rates matter, as well as delivery mechanism. Providing 18 GWh to a city as electrical potential over the course of a workday is essential to its operation. Unleashing it as thermal pulse, blast, and radioactive effects in a few milliseconds is highly disruptive.

Similarly, the Chelyabinsk meteor in 2013 was the equivalent of a rougly five hundred kT nuclear blast. That energy was released at a distance (roughly 20 miles / 32 km altitude), over time (several seconds), and in a form (mostly supersonic shockwave) that produced widespread damage on the ground (mostly broken windows and glass, some collapsed walls in weaker structures), but was not directly or indirectly lethal.

https://en.wikipedia.org/wiki/Chelyabinsk_meteor

Typo in title, should read Bennu not Bennui.

If there COVID-19 pandemic has shown us anything then that civilized humanity is unable to prevent catastrophe, but that it also will be able to mitigate the worst effects for the richest 20-30% of the population.

It is sobering, because there was always this observation that a common enemy unites people to strike effective action and we could feed our hopes that if things are just serious enough, we will be strong enough. But, the pandemic was that common enemy and yet we saw a failure to prevent it.

We shouldn’t even say it was due to egoism, greed or incompetence. It’s just impossible to coordinate on that scale.

Why would it be any different here?

The only difference is that we would be calling astrophysicists "heroes" instead of healthcare workers.

Hell, we might even clap for them at baseball games.

And meanwhile we would give them pay reductions because honor is worth far more than fake money

Dealing with an asteroid threat doesn't require hundreds of millions of people to get off their asses and actually do something about it. That's the difference.

It may require politicians to unite, to provide funding. Like global warming.

Has there ever been faster global vaccine deployment(s)? Did we have ANY coronavirus vaccines 2 years ago? Frankly an asteroid collision can either be mitigated at the nation state level or not (positive cooperation of course helps).

Apparently unpopular opinion- there was/is no coordinated super-effective thing that a united humanity could have done to stop the spread of Covid once it emerged. There's no One Weird Old Trick that prevents a new, deadly disease from spreading in a really interconnected modern world, unless you believe in utterly unrealistic policies like 'everyone on planet Earth coordinates to stay in their house for months to stop the spread'. Countries like Australia that were pretty authoritarian in preventing spread are now getting hit by more waves later on. Certainly there were tons of policy failures along the way, but the disease's spread was pretty unstoppable

The difference would be that there would be a clear outcome - many quick deaths, and a relatively simple solution - change it's trajectory or blow it up.

Afaik, everyone did follow lockdown orders in the first few months.

Then it became clear that the death rate isn't worth worrying about - yes, for the majority, 1-3% is clearly not enough. If it was 10%, if corpses were littering the streets, I bet the attitude would be completely different.

Then the conflicting messages started. Do this, do that, but not for these guys, they're essential or something. And not the rich, they can still travel. And you are vaccinated but still can get infected.

The governments didn't even try that hard, no one got forced, even now no one's forcing vaccination.

So the majority just stopped giving a fuck.

> The governments didn't even try that hard

Exactly. My impression was that there were no contingency emergency plans, every action was always only reactive and never preventive.

I still can’t understand how it is not possible to immediately impose lockdown measures after clear signs of rising infection numbers in order to quickly and swiftly prevent further escalation. Instead, at every wave again and again we had the same discussions and officials were starting to develop new emergency plans 4 weeks into exponential infection rates.

These are our elected officials and they are incompetent. It is our responsibility, our fault.

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