Bigger than the one he’s sitting on…?
We are decades from seriously starting to develop the tech. Nothing can be done about this one, even setting aside currently bleak-appearing politics.
If we had complete asteroid diverting tech today, and the worldwide decision-making arrangements today, we’d already be already real late in the game for this asteroid. The usual rule of thumb is we need to launch a mission about a decade before point of closest approach to have time to sufficiently alter it’s trajectory. We’re already too late. Even if we magicked all this stuff into existence overnight.
We’ll probably have better luck next time.
Unrelated to the above …
The usual way asteroid impact probability predictions go is they become more and more likely over time, getting ever more scary. Until suddenly they change to zero. Yep, zero. And everyone heaves a sigh of relief.
Why is that? And no, the answer is not that it’s a conspiracy of scientists to scare people for more funding.
The answer is the predictions about the asteroid’s future trajectory have error bars on every factor that goes into them. The result is that as the asteroid’s path is predicted to pass the Earth’s path, there is an ellipse of uncertainty. The asteroid will go by someplace inside this ellipse with the Earth predicted to also be someplace inside the ellipse. If when the time comes in 2032, they’re truly in the same place within the ellipse, we get an impact. If they’re in different places within the ellipse we get a clean miss. But right now, all we can say is the asteroid will be someplace in the ellipse come 2032. So far so clear?
As time goes on and there are more observations of the asteroid, the uncertainties in the data get smaller too. As the error bars on the trajectory prediction get smaller and smaller, the ellipse shrinks. So Earth occupies an ever increasing fraction of that smaller and smaller window of opportunity for a collision. Meaning the impact odds based on that prediction get larger and scarier. And this continues as more and more data comes in and the uncertainty range on the prediction shrinks. The Earth looms ever larger in the ever shrinking ellipse.
Until one more iteration and now the new smaller, improved error ellipse no longer includes Earth. Earth was in the bigger older ellipses, but not now in the latest one. So the impact probability is now zero. And every subsequent prediction will be the same way: zero probability of a hit.
There’s absolutely nothing anyone could do about it even if we knew there was a 100% certainty it would impact.
We’ve already done it once. It was less than a year from launch to impact.
DART sent a 1000 pound impactor into a an asteroid orbiting another asteroid, because that made it very easy to detect if the impactor changed the trajectory of the target. It did.
This was a test, but it shows we can hit an asteroid, and that hitting an asteroid with a heavy object can change the asteroid’s trajectory.
I’m not saying hitting and diverting 2024 YR4 would be easy or a sure thing, but saying there’s nothing we can do, and we’ve never done anything like it before is just wrong.
And years before that in the planning and prep. That’s fine for a known entity, not so much a sudden “Oh, shit, this thing is going to hit in a year” type event.
I can’t help be reminded of this from Futurama.
And even at that, it’s not a very big one. City-busting sure, but that’s it. And it’s FAR, FAR more likely that it would hit ocean or uninhabited land if it were to hit.
Impact crater from DART test as seen from Hubble.
That is a statement so long on exaggeration as to be functionally untrue.
As @MrDibble said, the planning was a decade+.
The actual impact was also many orders of magnitude below what would be needed to impart meaningful delta-V.
It also showed that impacting a rubble pile asteroid (i.e. most of them) is almost certainly not the way to change its trajectory. They’re flimsy enough you sorta need to put a net around it and then push / pull it very gently with a long-duration low-thrust motor. Which means you need to perform a low-speed docking with it first. Not a high speed impact. All that velocity matching takes time. Time you don’t need to just perform a head-on collision.
My bottom line:
Is DART real? Yes. Did it deliver a subscale impactor to the asteroid it was aiming at? Yes. Does that mean we can do more than zilch about 2024 yr4? No, it does not. Not even a little bit.
It’s certainly a step in the right direction. But by that standard so was Project Mercury and the early astronauts. We learned a lot about rocket launches with that effort.
It’s currently up to 2.3%:
I dunno. Spreading out the rubble would be a benefit. The impact energy is about that of a good-sized hydrogen bomb. Bad news if it hits a city. But spread out, it’s not so bad. The goal isn’t to deflect it, but rather ensure it doesn’t all hit the same spot.
Looking at those dots, the tall part of the probability distribution is evidently the equatorial Atlantic ocean or just onto the African coast along / above the Gulf of Guinea.
Good update here with details of the most recent measurements:
Could be a very interesting day in Earth history. Just 7 years 11 months to go.
The good news, as said upthread by several folks, is the range of sizes for this thing makes it a city killer, not a planet killer. It’s interesting to me that the swath shown in your dotplot or the one in the wiki article looks like ~50% of the potential impact points are on land. Given the land/water mix of Earth overall, that’s a bit unlucky.
The Atlantic is just a rinky-dink ocean. If the impact track had been on the Pacific side, there’d have been plenty of space.
I’m not competent to speak knowledgeably on this one.
I expect that converting a rifle impact to a shotgun impact would be helpful for asteroids up to a certain size. Imagine converting the whole thing to a cloud of sand 10,000 miles across. Some would miss Earth, and most of it would burn high in the atmosphere. The total energy deposition would be the same, but more diffuse in space and time. And all of it in the upper atmosphere, not here at the ground.
What the longer-term effects of that would be would be are beyond me. But the prompt effects on the ground would be fairly minimal other than a brief thermal pulse.
OTOH, for a big enough asteroid, say a county or US state-wrecker that impacts intact or nearly so, a lot of the total energy budget is spent overkilling the point of impact. Fragmenting that into a shotgun blast of city killers may just make the problem on the ground a lot worse. Lots more total land surface is rendered devoid of life at least for today. Lots more square miles of human infrastructure is destroyed. etc.
Bottom line: I know I don’t know, but I can make arguments that sound plausible to me that a shotgun impact is not always better than a rifle impact.
Anyone have any ideas, or better yet, cites?
To be clear, my comment about fragmentation is specifically about this asteroid, which is 40-90 m diameter. Mostly it’s based on intuition–this is a Tunguska-scale asteroid, which would cause immense damage in a local area, but the energy is not very much in the grand scheme of things. It’s the amount of solar energy that hits 250 km^2 in a day. Minuscule if it’s spread out enough.
So the main question is whether we can actually disperse it with current technology. The papers I’ve seen do seem to favor deflection rather than fragmentation, though fragmentation isn’t ruled out for this size. A couple of examples:
NEAR EARTH ASTEROID ORBIT PERTURBATION AND FRAGMENTATION
DEFLECTION AND FRAGMENTATION OF NEAs
~100 m is actually in the “nice” range. It’s small enough that we can actually do something about it. Much smaller and there’s no need to do anything; much larger and we can’t do anything. The latter link says:
You can send a rocket on an intercept course and give it a decent impulse (as long as you have enough warning). 7 years is on the low side but still enough time.
The other paper mentions:
~1 kt sounds like a lot but isn’t so bad. A fully-fueled Starship can easily achieve that kinetic energy. A 100 ton tungsten slug at 9 km/s is about 1 kt of energy. If you can hit the asteroid head-on, you can get a lot more KE out of it.
If you can strap a nuke to it, you can do even better. But it would be nice to avoid that.
The Odessa fall was a shotgun blast, with the largest crater being currently around 168 meters across and 30 meters deep. A lot of googling came up with a 1960s estimate that the largest crater was made by a fragment around 4 meters in diameter. The Canyon Diablo impactor is estimated to have been between 30 and 50 meters in diameter. So if CD had been a rubble pile of Odessa-sized fragments, it could have made around 500 to 2,000 Odessa-sized craters. That’s neglecting that the much larger surface area would have meant much more ablasion, but still the shotgunning wouldn’t be great.
4 m seems kinda small for that size crater, though it was iron, so maybe. On the other hand, the Chelyabinsk meteor was 18 m diameter and never reached the ground. Caused some broken glass but nothing serious.
2024 YR4 is thought to be a stony asteroid, like the Chelyabinsk one, so meter-for-meter it’s probably on the less damaging side of things.
Indeed, the first step in any serious planetary-defense system is much better detection capability. Enough that we can detect all of these rocks, and get enough data to determine which, if any, will eventually hit, enough decades in advance that we have time for all of the other aspects of planetary defense. Indeed, even in the worst-case scenario, the detection system would be enough, by itself, to prevent human extinction, should we get something else on the scale of the Great Dino-killer (though of course, we’d really like to do a lot better than “prevent extinction”).
My source is this PDF.
“The fragment that produced the main crater was estimated to be ~4 m diameter and to weigh 315 tons (Baldwin, 1963).”
(Second page, second paragraph.)
Scott Manley did a video on it:
Says it’s not a rubble pile. Rotation rate is too high for that.
I’m mildly inclined to grab one of NASA’s mission planning tools to see what kind of delta-V you could get from a mission. You could do a lot of damage if even a portion of the asteroid’s relative velocity could be used. If it hits Earth, it would be at about 17 km/s. If you could get a 25 km/s relative velocity (spacecraft+asteroid), a Starship with a 100-ton penetrator would be equivalent to a 7.5 kt bomb.
Thanks. Typical rule of thumb is that the crater will be 10-20 larger diameter than the object, which would imply <80 m for a 4 m object, but that’s just an approximation. On the other hand, I’m not sure what kind of estimate they did back in 1963.