'Planet killer' asteroid found hiding in sun's glare may one day hit Earth
space.com
space.com
> scans the sky during twilight hours when these asteroids can be detected within two 10-minute periods each day
20 minutes per day per telescope. Talk about an under investment in something that may save our lives. I hope that we can soon launch more space based telescopes capable of observing the inner orbits 24/7 using some kind of sun shade or occluding device. We need to dedicate a lot more time and resources to this.
Even considering just astrophysics, we have more pressing problems.
An asteroid caused the extinction of the dinosaurs, which led to the rise of the mammals, which led to us, so that's a negative number.
But it should be an example to us, to not risk the same fate.
We can't engineer ourselves out of an asteroid impact. Yet.
A powerful earthquake even it hits a large city would wipe out only in millions at worst.
They do not scale the same way.
WW1 too apparently
https://www.rafmuseum.org.uk/research/archive-exhibitions/wo...
Someone feed this to an AI thing, I need this book.
What truth is there to this? Suppose this asteroid was on a collision course with earth, would we have any recourse other than praying it lands in Siberia and not NYC.
The sooner the threat is detected the lighter the necessary response
>...praying it lands in Siberia and not NYC.
The Siberian Tunguska event was thought to be caused by a 20m diameter object hitting the earth. This is talking about a 900m diameter object which likely has 100,000x the mass of the object that hit Tunguska.
EDIT (per comments below):
400,000x the Chelyabinsk object
27,000x the Tunguska object
Article says it's 0.9mi, so 1.5km
> 20m
That was Chelyabinsk, Tunguska is thought to have been 50-60m
Astrodynamic Fundamentals for Deflecting Hazardous Near-Earth Objects - https://www.adrc.iastate.edu/files/2012/09/IAC-09.C1.3.1.pdf
That paper goes into the what it would take to divert an asteroid (with emphasis on Apophis).
However implementing a system to defend against asteroids even with short notice is feasible. We can make rockets much larger than ICBMs and put them on standby for planetary defense. You'd presumably put appropriate sensors and maneuvering thrusters for getting to the approrpiate position near or on the target, akin to the interceptors used in missile defense. Interceptors would have a dedicated 3rd stage like the Centaur to launch them on trajectories away from Earth - the further away the interception the smaller the necessary deflection. Ideally you'd catch it early and start the deflection so far away that a kinetic impactor or even just the craft's gravitation would nudge it to a safe course, but for short notice you need to go nuclear.
Breaking up an asteroid into smaller pieces with a nuke is possible, especially for the subset of asteroids which are basically loosely held together piles of gravel. Some people think this is a bad idea as instead of 1 big rock to deal with now you have lots of little rocks that are also radioactive, but that actually is a much preferable situation. The ability of objects to pass through the atmosphere is dependent on their diameter, lots of small rocks will burn up harmlessly while a single big one will impact. The radioactivity from the nuke would be spread out extremely dilute, and specific nuclear weapon designs which minimize neutron activation can keep the radioactivity very low. A more serious concern is that you don't know the trajectories of the resulting fragments, some of which might still be dangerous, and thus it would be a very bad idea to destroy it before impact was a certainty, but then waiting until the last minute to stop it is a major risk in itself.
More safe would be to detonate the nuclear device near the asteroid. This would vaporize a thin layer of the surface of the asteroid in line of sight of the explosion, sending it flying off into space at extremely high velocity and propelling the asteroid equally in the opposite direction. There are two major advantages to this approach: it will work against targets regardless of their composition and internal structure (very beneficial if we don't have time to study the asteroid ahead of time) and the method can be done repeatedly to the same target - we could launch dozens of independent interceptors and just keep detonating them one by one until we get the desired result. While the goal is to have the asteroid not impact at all, and thus radioactivity is even less of a concern, this option does produce even less radioactivity than blowing up the asteroid. From a strictly technical perspective this option is pretty much a no brainer, but obviously building a battery of dozens of nuclear missiles is politically problematic.
Section 6.1 is on nuclear stand off explosions.
> The nuclear standoff explosions require an optimal standoff distance for a maximum velocity change of a target as- teroid. Therefore, we have to determine how close the nuclear explosion must be to effectively change the or- bital trajectories of asteroids of different types, sizes, and shapes. The precise outcome of a NEO deflection at- tempt using a nuclear standoff explosion is dependent on myriad variables. Shape and composition of the tar- get NEO are critical factors.
Section 6.2 is on kinetic impacters...
> A somewhat futuristic, solar sailing mission concept utilizing a 160-m solar sail to deliver a 150-kg kinetic impactor into a heliocentric retrograde orbit was studied in [25-28]. Such kinetic impactors will result in a head- on collision with a target asteroid at its perihelion (as illustrated in Fig. 1), thus increasing its impact velocity to at least 70 km/s. The NEAR Shoemaker study of as- teroid Mathilde and the Japanese Hayabusa mission for exploring the asteroid Itokawa suggest that many aster- oids are essentially “rubble piles.” Consequently, a practical concern of any impulsive approaches employing kinetic impactors or nuclear explosions is the risk that such high-energy deflection attempts could result in the frag- mentation of NEOs, which could substantially increase the damage upon Earth impact.
And then, section 6.3 is a fun one: Gravitational Binding Energy
> the disruption energy per unit asteroid mass is predicted to be 150 J/kg for strength-dominated asteroids. This indicates that a strength-dominated, 200-m asteroid would not be disrupted by a 150-kg impactor at a high impact velocity of 70 km/s. Also in Ref. 5 (pp. 135-136), the energy (per unit asteroid mass) required for both disruption and dispersion of a 1-km asteroid is predicted to be 5 kJ/kg. Thus, the feasibility of the most kinetic-impact approaches for either disrupting or deflecting an incoming NEO depends on its size and composition (e.g., solid body, porous rubble pile, etc.), as well as the time available to change its orbit.
These are from 2012, and we've had a decade more experience (and a mission to try it out) since then... but it's interesting to look at and the math in the paper doesn't change.
Now some massive swarm of space pebbles should do the same, given it's large enough?
Ahw, so many shooting stars! And then you feel the heat.
The most powerful explosion may at most reduce the size of the biggest chunks, but not change the vector velocity of the barycentre at all.
It feels like smashing any available rocket into the side of a non accelerating body would be effective, but space physics is weird, so I must be missing something.
If your asteroid is only 20 to maybe 400 meters across, having it land somewhere absurdly remote on land or far off into the deep oceans would minimize harm, but for asteroids much bigger than that (and even 400 meters is really stretching the bounds of acceptable size), it doesn't really matter where the impact happens, millions or more people will almost certainly die.
If you scale up to a size of, say, 900 meters or larger, then you're talking global multi-year catastrophe no matter where the impact is.
If you then scale up to over a mile or two in diameter, then you're talking global multi-decade cataclysm no matter where the impact site is.
So yeah, even with Siberia, the Canadian North, Antarctica, the Sahara or the central pacific ocean. Any size beyond a few hundred meters makes specifics not so important in terms of death toll and major climate effects.
"But we have enough problems down here that need fixing!", "The odds of all civilization being destroyed by that asteroid is only .5%!", "It will cost too much and the odds are low"
You'd think protecting all the things we hold dear, family, culture, art, friends, the future - would be a priority.
You need momentum, and no explosion can provide any global momentum.
https://www.space.com/dart-asteroid-crash-first-photos-licia...