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Three trajectory models of the Chelyabinsk meteoroid compared
[April 5: Help scientists to more accurately calculate the trajectory. Visit www.russianmeteor2013.org to contribute videos or help with the analysis.]
I now have three trajectory models of the Chelyabinsk meteoroid to share in Google Earth, from the three teams I am aware of who have published detailed results. The resulting KMZ file comes with a useful new feature: I’ve added geopositioned screenshots of the most useful videos, so you can now “fly” into each vantage point to check how the computed trajectories compare to the view in each video from the location it was taken. Here’s a quick tour on YouTube of the KMZ file :
Briefly, here’s what I’ve done: Initially, Google Earth allowed us to locate and measure YouTube videos to determine the angles of shadows, which enabled trajectory calculations, which have now been visualized in Google Earth. These trajectories can in turn be inspected visually from the vantage point of any number of geopositioned videos, resulting in an interesting additional method for verifying the accuracy of diverging trajectory calculations, short of going to these locations and making measurements in situ.
Before I do a walk-through of the trajectories and the videos, an exciting piece of news: A week or two ago, Jorge Zuluaga and Ignacio Ferrín — the duo calculating the trajectory of the meteoroid at the Physics Institute at the Univeristy of Antioquia in Medellín, Colombia — got in touch to discuss my original blog post on the use of Google Earth and YouTube as an ad-hoc sensor network for raw data on the meteoroid. They had taken my method and given it a rigorous mathematical make-over, aggregating information from four especially useful videos, including those contributed by commenters on Ogle Earth in the days after the event. From this trajectory, they calculated an orbit , concluding that the Chelyabinsk meteoroid was an Apollo-class Near Earth Asteroid.
In a classy move, Jorge and Ignacio asked me to co-author the paper they were writing, for having originally come up with the method which they then greatly improved upon. In the ensuing collaboration we identified additional useful videos, worked on the included Google Earth visualizations, and honed the prose. The paper, The orbit of the Chelyabinsk event impactor as reconstructed from amateur and public footage , has just been published to arxiv.org ( here’s the PDF ). The KMZ file discussed in this post ( download and open in Google Earth ) is the one attached to the paper. Note that the paper makes a point of thanking several commenters by name for their contributions to the original blog post . Citizen science FTW!
Now for some notes on the different trajectories:
Accuracy I: The NASA trajectory (in red) is derived from coordinates courtesy of Sebastien Pauleau, who calculated them from a close study of the trajectory map NASA released here , modeling the result on a WGS84 datum globe. He reports that while the accuracy of his model is calculated to 4 decimal points (an error of within 10m around Chelyabinsk, the limit of Google Earth’s accuracy with respect to the positioning of its imagery), it’s not possible right now to know how accurately NASA plotted its map. The Colombian trajectories (pink, green, black, orange), are also plotted to 4 decimal points, while the Czech results (blue) are plotted to 3 decimal points (within 100m), though of course the real error bars are a lot larger in at least all-but-one case (or else all the calculated trajectories would all have to lie within 100m of each other). The Colombian coordinates were shared directly; the Czech coordinates were published here .
Landing sites: We know that a good-sized chunk landed in Lake Chebarkul, and in the original coarse calculation I used that information as an input, fixing the lake as an endpoint for the trajectory. None of these more accurate “pro” trajectories make this assumption, and it is clear from subsequent news articles that the landing area extends beyond and around the lake. As a result, all calculated trajectories overshoot Lake Chebarkul, intersecting Earth just past the town of Miass.
Accuracy II: Because all these calculated trajectories are straight lines, there is an important caveat: From having looked closely at many geopositioned photos and videos, it seems clear that the real trajectory of the meteoroid changes as a result of the main explosion just south of Chelyabinsk. The post-explosion path seems to aim at bit more steeply at Earth, and may even have changed its azimuth (direction). Also, as the meteoroid slows down through atmospheric friction, it will begin to “fall” in a more classic arc. No one straight line can model such a more complex path with complete accuracy.
As a result, I think all current calculated trajectories overshoot the real landing site. I suspect most of the meteor mass landed between Lake Chebarkul and Miass, not beyond Miass. There are no videos from Miass showing a path flying overhead, though the calculated trajectories do assume such a path. One Miass video in particular (“Miass, near chimney” shows the contrail almost perfectly head-on, suggesting the the main part of the meteoroid landed in front of the viewpoint (towards Chebarkul).
Other viewpoints in Miass (“Miass, near plant” especially) suggest that some of the calculated trajectories do a better job of modeling the pre-explosion path, while others are more accurate for the latter part of the path. It’s important to note that around Miass, because the meteoroid was so close to Earth, very small differences in the calculated path can have a very large perceived effect, with changes of just a few hundred meters radically altering the perceived view.
From what I understand, it’s possible to construct even more accurate trajectory models that do not assume a single straight line, and I think this is where astronomers’ efforts will lie in the future.
Accuracy III: One word of caution about the geopositioned screenshots in the KMZ file: It’s not possible to accurately compensate for fish-eye effects and other distortions in Google Earth beyond basic field-of-view adjustments, and the videos do not always contain sufficient environmental references to precisely measure the heading, tilt and roll of the camera viewpoint. So these videos cannot be used for detail work, though they do work well when trajectories diverge greatly, as is the case near Miass.
Interact: The KMZ file is fully editable, so feel free to edit the embedded screenshots (Right-click an item in the Places sidebar, select Get Info) to see if you can get a better fit against the calculated trajectories. Although it is tempting, I tried not to align the meteoroid path in the video capture with the calculated trajectories in Google Earth, relying instead on clues from the surrounding environment. It’s possible to infer quite a lot from aligning the placement and angles of objects in the geopositioned video capture with imagery on the ground.
Interact II: Do play with the opacity slider at the bottom of the Places sidebar (click the gradient button, if you need to); this makes it much easier to make comparisons (watch the video above to see how). Finally, if you’re wondering how I managed to fly around so smoothly in Google Earth — I use this to navigate 3D space.
40 thoughts on “Three trajectory models of the Chelyabinsk meteoroid compared”
- Pingback: Reconstructing the Chelyabinsk meteor’s path, with Google Earth, YouTube and high-school math | Ogle Earth
- Pingback: Chelyabinsk meteoroid: Comparing paths with the pros in Google Earth | Ogle Earth
Great Post Stefan. The embedded video captures really help. Alone ‘Road near Miass’ seems to confirm the average colombian trajectory. What puzzles me is that the two most reknown teams (Czech and NASA) have two very intricated trajectories that both seem to be slightly off the real thing.
- Pingback: Eπιστημονικά συμπεράσματα από ερασιτεχνικά βίντεο | physicsgg
“Excellent work and updated model, Stefan: Interesting to see how your ‘amateur footage’ and calculations/projections compares with the ‘professional trajectory announcements’ from the relevant organisations/authorities too, and which are also quite vague in some respects…. (but to be fair they appear to have relied primarily on infrasonic monitoring, which may account for such vagueness?).
Clearly not all the (reportedly evaporated) 11KT of the initial mass (plus the 100Kg of small meteorites found so far) accounts for it all….Again those videos show a large incandescent object surviving past the airburst/s (and it did not all go in the Lake…) – My own calculations predicted this larger fragment landed halfway to Ukraine (but my cold air resistance/density gradient and gravitational assumptions etc may be incorrect !) Now all we have to do is wait for the snow to melt so these possible impact sites can be properly investigated. “
The NASA calculations are extremely approximate and seem to have been based mainly on a mixture of the blast size and/or trajectory via the infrasound detection system (which as you know is usually used for Nuclear activity purposes). Indeed NASA themselves accept this data as very approximate (and even state the blast size as between the radiated (ie. detected) energy and the total (including kinetic) energy as 90-440KT of course).
In my opinion it is much more intelligent (these days) to take those ‘amateur visuals’ and other data and thence extrapolate on that basis: Even with a given range of trajectory estimates the errors in such calculations are reduced (and also largely quantifiable, too !)
When I did my own calculations about the remaining (major) segment from this event I also (reasonably) took into consideration the increasing density of the air as the altitude reduced and also the air resistance variations at various heights/temperatures, too. As you will probably know these factors result in a rather curved (and increasingly steep) path, and also that at some point a terminal velocity is achieved… The biggest errors however are in determining the likely ‘vector’ effects (ie. both in terms of velocity and direction) on the surviving segments as may be caused by a c.100KT airburst… Thus I was led (or possibly misled…) into believing an impact site for a major segment could well be much further west and further south (than Miass) was possible…. We will see !
I will re-work my data if/when more details emerge and let you know !
– and for those interested in the infrasound monitoring network used, see:
– note there is also more accurate tracking data available from various orbiting defence/military satellite systems, but this information will not be made public.
Submitted as additional information on behalf of davew:
My post above was (also !) slightly vague -as it was originally intended just as a note for Stefan- but here are some more of my views/comments/data on this for anyone else contemplating such calculations:-
-As we know the object impacted the atmosphere at a shallow angle, ~17 degrees from horizontal; first became visible at ~90Km altitude, and then ablated for the next 10 seconds or so before exploding at a height of ~30Km and (parts) continued to be visible for about another 7 seconds or so. This is well represented/recorded and thus the video evidence has produced several excellent extrapolations, as explained extensively within the video:
The path of the object (even at 17km/s) curves gradually (and increasingly) however once the object hits the atmosphere and resultant ablation rapidly occurs, and the curving worsens as the air density increases of course. Thus the object loses a high percentage of its original mass en route through the atmosphere, typically 90% under these circumstances (but which would also thus mean there is c.50,000Kg as yet not ‘fully accounted for’ ?).
Calculating the (final) curved path is complicated therefore by the rate of mass loss and this relies on estimates of the initial mass size/shape/composition, (the latter assumed from the pieces recovered so far to be an ordinary chondrite), the various gravitational effects on this shrinking/slowing mass and also the increase in air density as the altitude decreases; Overall quite an equation, however….
The operative word above is ‘estimates’ of course, with resultant approximations and calculation errors… including the fact that in falling the remaining c.30Km the surviving fragments will also attain a terminal velocity…
For example, using the optical projections (only) and these kinds of estimates it is possible that ‘the’ surviving fragment is in Lake Chebarkul – ie it simply ‘dropped short’ of the projected impact sites due to the atmospheric effects mentioned.
However, based on the likely size of the (any) fragment in the Lake it still does not explain what exactly happened to the remainder of the object as it ablated/evaporated/exploded ! Nor does it explain what happened to those emerging fragments which were not visible, either, in the ‘strewn field’ etc. Those parts which vapourised will be present (and distributed far and wide) as condensed spherules, too. Moreover it overall also still casts some doubts on estimates (and/or composition) of the original incident object..(?)
Moving on one can only hope that as the snow melts many other pieces (of the meteoroid and the puzzle) are actually found !
It seems to be coming more clear that the main explosion represents some sort of demarcation point. Flight before that point can be extended back into space to calculate the previous orbit and flight after that point may lead to where debris was strewn and any larger fragments may have impacted.
I am intrigued by /watch?v=c0AQmFnXQyQ and by /watch?v=v=y7VvBxJXG7E at 54° 50’ 56.53″ N 61° 33’ 15.14″ E (if I am reading the right comments) and by /watch?v=umBdOycWLDA at 54° 48′ 51.16″ N, 58° 26′ 0.97″ E. I’m fairly sure the main explosion ejected some fragments sideways to the left (as seen along the direction of travel) but I can’t prove it.
Important note. Some links in this blog appear to no longer work, especially those to http://www.youtu.be/ but this is easily fixed. Delete the “www.” part from the URL and the link will be working again.
There are voices that question some aspects of this meteorite: – narrow atmosphere horizontal entering angle: ~17 degrees (the lesser this angle is, the greater is the chance for the object to miss the Earth) – just one explosion in meteorite’s disintegration – explosion sound was not heard in ~90 km west of Chelyabinsk(by comparison, the Sikhote-Alin meteorite was heard from ~ 300 km) – brown trails left on the sky, similar with a burned fuel used for rockets So, the question would be: was it actually a nuclear rocket disguised in a meteorite-like form ?
To my eye, hundreds of videos show it behaving exactly like a meteoroid is expected to behave.
I also don’t see a relationship between angle of attack and probability of missing earth.
The main point here is that all such events are essentially unique; Unfortunately comparisons are inevitable (even if inappropriate, as we have simply not seen enough such events): That said some aspects of this event are certainly ‘similar’ to the “Grand Teton” (’72) event, and which was a ‘grazer’ due to a very shallow angle of attack:
@g1smd: A great compilation there – 450+ videos – unprecedented ! From all these additional visual extrapolation should certainly provide many more (‘straight line’) trajectory estimates and directional data approximations. Again the complete breaking up of the object (especially into ‘dark flight’ fragments) makes strewn field deductions more difficult of course. -That fragmentary diversion ‘to the left’ you mentioned is why I suggested looking further south (and west) for the larger fragments, too !
– and in answer to the ‘nuclear rocket’ question above and (in spite of Chelyabinsk’s long association with nuclear research) there is -unfortunately- no such technology (and neither is there ever likely to be which could be used to launch from Earth). There are ION rockets which can be used once in space, however these are only suitable for very slowly-accelerating spacecraft, and can be powered from a small ‘nuclear’ source (akin to a ‘thermocouple battery’) which I suspect is why sometime folks refer to ‘nuclear rockets’ – or similar !
The ‘brown trails’ as observed here were simply vapourised rock/particles, ie. NOT a vapourised rocket…
Latest reports emerging from the Russian press are now stating that the object was ‘initially 10,000-18,000 tonnes – and the size 17-20m, with around 10% reaching the Earth’ (=1,000-2,000 tonnes) but that ‘Chelyabinsk was only exposed to “about 1 kiloton of energy”….’
So, just a few thousand tonnes still ‘missing’, then ?
As you mentioned davew, the strewn field makes it ‘easier’ to find fragments everywhere, for a strewn field is usually elliptical and broad. The 3 or 4 biggest visible remains from the videos might nevertheless stay on one of the main calculated trajectory.
@SebastienP; I agree, plus the ‘Strewn Field’ here is even greater and more diverse than for a ‘standard’ break-up – due to the explosion/s of course – and so may well cover an area over 10K square km… It will be interesting to see just what is found (and when); For example if there *is* a fragment in the Lake it will probably be a lot less than 2m diameter, though ?!
Maybe the attached link, for a ‘typical’ chondrite, gives an idea of just what we could expect to find (in the Lake), although this fragment is ‘only’ c.90Kg & measures c.50X40cm; Note the fragile/cracked nature of the object, due in part to ablation/cooling effects in transit through the atmosphere: There would originally have been a much more burned/blackened appearance of course (but this has been ‘weathered off’, as this one fell to Earth 10K+ years ago)…
http://www.lpi.usra.edu/meteor/metbull.php?code=56144 Image: http://theheritagetrust.files.wordpress.com/2012/08/stonehenge-meteorite.jpg – Alternatively (image) search on ‘Wiltshire Meteorite’ or ‘Lake House Meteorite’
Another ‘similar’ example is described in:
Again ‘only’ c.70tonnes but very little was found…
Help scientists to more accurately calculate the trajectory. Visit http://www.russianmeteor2013.org/ to contribute videos or help with the analysis.
So, not only a strewn field but also a huge dust cloud ? :-
Hi Stefan,hi all, there is another aspect we could talk about and perhaps investigate… Mysterious electrophonic noises have been heard at the very moment the Chelyabinsk meteor was entering the atmosphere. 27 people have reported it within a week of the Chelyabinsk fireball. Normaly, no sound of explosion can be heard before dozens of seconds. But the electrophonic sound appeared to some when the meteor was still flying. This is a known phenomenon, not yet understood that we could analyse in this thread if we find the source of the reports (sadly, not linked in the article below).
“Within a week of the Chelyabinsk fireball, a Russian website collecting testimonials had 27 independent reports of people hearing weak but clear hissing sounds during its flight. Many compared the sound to a “Bengal sparkler,” a type of hand-held firework popular in Russia. And one person described the noise as “a low-level crackling hum very similar to what you hear near high-voltage power lines.”
Most of those who heard sounds noted that they could not determine either the source of the hissing or its direction — precisely the features that had puzzled previous observers. One witness, however, was certain the noise came from a telephone cable running from a street pole to her house.
The reports seem to have come only from observers in quiet rural areas. In the city itself, and in the vehicles carrying the now-ubiquitous dashcams, background mechanical noises appear to have masked the meteor’s sounds.”
Yes, it is an interesting phenomenon (and similar observations have been made ever since telegraph/phone lines have been in use, particularly from lightning sources…)
Basically as a bolide impinges on the ionosphere (and then atmosphere) multiple-frequency Radio Waves are produced of course – particularly including VLF RF – and these can interact with such wires, and other objects, which act as ‘receivers’/secondary radiators (as the RF energy is demodulated into sound); This is why the source is indistinct, as such receivers/radiators/demodulators can be located anywhere/everywhere around the observers/s !
Yes Davew, this is I think the status of research. But this hypothesis is only resulting of the analysis of witnesses’s reports. And for now, as far as I know, nobody ever measured the incoming RF as a sound was being heard. I’d like to think that the RF are interfering with wires, but I know at least of one case in a car (no cables, not really a quite place either) so that I’m not sure at all. Some think that this is only the surprise of witnessing something highly unusual. And indeed, the two witnesses I personnaly know of have only witnessed one meteorite in their lives, whereas friends astronomers of mine that have seen dozens of bolides have heard it only once or even none. To better find out, I think it would help if the Electrophonics sounds databases around the web would be “open”. Because all I’ve said can be contradicted as there is no casuistic available really.
This is the article that spoke of 27 witnesses in last february: http://chelyabinsk.ru/text/newsline/625214.html
The Cheliabinsk dedicated database that recorded the 27 witnesses but which is “closed” (or seems to be): http://www.chel-meteorit.youini.ru/
Response by davew posted on his behalf (he had trouble posting here):
As we know, this is simply an unusual event, and, with only c.30 witnesses out of (say) 300K observers here it is likely to be (and stay) relatively rare (and hence difficult to investigate in detail and in a truly scientific way) !
As I stated It does not *only* happen with wires, RF radiation impinging on ‘other objects’ (metal or not) can produce this effect….
Remember we are dealing with hypersonic vapourisation of rock/minerals/elements so we should thus expect some ‘interesting fireworks’ and ‘very unusual effects’ of course.
I am not sure why you maybe think such effects are ‘secret’ either – as there is lots of (publicly-available) research on the high energies produced by ‘shock vapourisation’ (of rocks) etc. With bolides the levels of released energy *naturally* thus produce RF/light/heat/sound (and effects) galore !!
However we also know that there are highly-sophisticated ‘sound monitoring systems’ around the world (to monitor terrestrial seismic event – including man-made ‘explosions’) so don’t be too surprised if the information about these systems is not so readily available: I am sure though you read the reports about the reverberations from this bolide lasting for many days for example (?)
No, that I didn’t know. I only have hard times finding the relevant testimonies that I’d like to analyse myself – others would probably like too, from this particuliar bolide or any other that shows such reports. If you or anyone knows about an available reports database of electrophonics effects, I’d like to see it.
I was referring to research on ‘shock vapourisation’ of rock, such as experiments/work like this (for example using lasers on quartz):
– and there is a long list of additional references at the end, too.
As for any ‘database on electrophonics’ effects.. Again this is simply so rare that -unless we are lucky enough to have some suitable monitoring-equipment at a suitable location – will probably remain essentially anecdotal or speculative… Otherwise it is simply an electomagnetic-energy to sound-energy modulation/conversion as I explained above (?)
Incidentally, back more on topic it seems that a meteorite fragment (c.60cm/300Kgm) has now finally been detected at the bottom of Lake Chebarkul – but not yet raised…..
Also interesting to note that some of the other (small) fragments found will be incorporated into the Gold Medals for the Winter Olympics !!
*This* is the source of the meteorite0in-the-lake story:-
Note that there is apprently also an unidentified 6m-diameter object down there, too; Good to note that all the UFO-believers did not get excited about this at least…..
Fragments now being recovered:
Still waiting for that biggest fragment (so far) to be recovered….
‘In other news’ there has been a statement that the meteor fragments that have been found have a characteristic ‘dark surface’ … and that this – in part – is why we ‘did not see it coming’. Considering the size/speed/original trajectory/etc of the object then with all due respect it seems rather naive to blame this ‘oversight’ on the colour …. ?
There have been some interesting images of the bolide from satellites however:-
Some other useful comments on Trajectory etc can be found in this Paper:
Interesting that, like me they caculated an impact point further South that Lake Chebarkul – but my strewn field was further East, too !
-Air resistance is a key (trajectory) determining factor of course but I am not sure that the wind speed will have that much effect though as suggested….
News today regarding recovery of the large fragment:-
Authenticity yet to be confirmed but other photos/videos of this I have seen look genuine enough (!)…. and it is also definitely ‘shock fractured’ too.
Now all they have to do is to find those pieces I predicted/expected from the (larger) strewn field; Smaller pieces to the East of Lake Chebarkul, bigger ones to the West !(?)
– And some better photos of it now on display:
Thanks for that davew!
Seems like the Russian Scientists involved now also accept there may be ‘missing pieces’ to this puzzle elsewhere, too ! :-
Wonder if they will even be found ?
An interesting video – it *almost* captured the impact ! I had to watch several times to discern that ice/snow/water ‘ejecta’ cloud though…
More analysis/extrapolations have now been published in ‘Nature’ :- http://www.nature.com/nature/journal/vaop/ncurrent/full/nature12671.html – Note how the extrapolations were complicated by those quickly-rising ‘vapour trails’
Similarly the predictions for the fragments (and see Table ‘d’):- http://www.nature.com/nature/journal/vaop/ncurrent/fig_tab/nature12671_SF6.html – I am a little biased but I suspect they are also now intrigued as to how such a huge object has apparently produced such a small strewn field, too !?
Additional detailed analysis of strewn field and trajectory data:
Still quite a lot ‘missing’ though ?!……
At the AGU Meeting (December 9) it was in fact described as an ‘Airburst’:-
As for the ‘Lessons Learned’ ? IMHO that we can *not * accurately predict such events, in part because they are all essentially unique – and even if we could ‘see them coming early enough’ there is actually -so far- very little we could do about it quickly enough to avoid the related terrestrial destruction and damage (?!). Yes, Nature can be cruel sometimes…..
Comments are closed.
Notes on the political, social and scientific impact of networked digital maps and geospatial imagery, with a special focus on Google Earth.
February 15, 2023
The Asteroid Blast That Shook the World Is Still Making an Impact
The Chelyabinsk asteroid slammed into Earth’s atmosphere 10 years ago, the largest impact in more than a century
By Phil Plait
Contrails left by the Chelyabinsk meteor over Russia.
Ten years ago, as the sun rose over Chelyabinsk, Russia, the sky exploded.
On February 15, 2013, an asteroid slammed into Earth's atmosphere at nearly 70,000 kilometers per hour. Almost the size of a tennis court, it blazed brilliantly in the sky as if a second sun had appeared and begun racing from southeast to northwest .
Ramming through the air at hypersonic velocities blowtorched the surface of the asteroid, which left behind a thick trail of vaporized rock as it screamed over Earth. The immense pressure started to flatten it (scientists call this “pancaking”), and the force finally overcame the asteroid some 40 kilometers above the ground. It crumbled into smaller chunks, each one still traveling at more than a dozen times the speed of a bullet fired from a rifle. These fragments also pancaked, creating a series of brief but powerful flashes of light as they heated to incandescence. The remaining pieces vaporized.
All of this happened in mere seconds, with the ultimate blow occurring when the asteroid was about 30 kilometers up. The energy of its last motion was converted into heat in an instant. The resulting huge fireball briefly outshone the sun in the sky, emitting energy equivalent to the detonation of about half a million metric tons of TNT.
The shock wave from this explosion traveled away from the blast, taking about a minute and a half to reach downtown Chelyabinsk, roughly 40 kilometers to the north. The industrial city of a million people was just starting its day when the apparition blazed across the sky. The awesome spectacle and the long, lingering vapor trail brought people outside or to their windows to see what happened—and that's when the shock wave touched down.
A tremendous thunderclap shattered windows all over the city, and flying glass was the source of most of the injuries to the roughly 1,500 people harmed in the event. Fortunately, no one was killed, and infrastructure damage was relatively minimal. Had the asteroid been bigger or made of metal or if it had plunged downward at a steeper angle, this story could have been quite different, the aftermath far more severe.
Chelyabinsk was a wake-up alarm for Earth —a loud one.
It was also a major learning experience for scientists, as it was the largest known atmospheric impact since the Tunguska bolide in 1908 . The asteroid's smoking trail was viewed by satellites as well as by thousands of eyewitnesses and cameras. Meteorites rained widely, including one monster half-ton chunk 1.5 meters across that plunged into a frozen lake and was later recovered. There's even security-camera footage of that piece crashing, creating a dramatic plume of snow and water shooting up into the air.
The meteorites recovered from the event revealed the asteroid's violent history . Shock veins riddled them, leaving narrow fissures. These showed that the 19-meter-wide Chelyabinsk rock was once part of a much larger asteroid that itself had suffered an impact, which broke off the piece that smashed into Earth and cracked it throughout. Radioactive dating indicated that the first impact may have occurred as long as 4.4 billion years ago, when the solar system was less than 200 million years old. Those fissures in the Chelyabinsk rock weakened it, allowing it to more easily disintegrate high above the ground and create that massive shock wave. The ghostly fingers of an ancient deep-space impact had reached out and touched the lives of thousands of Russian people that day.
It's not clear which asteroid may have been the parent asteroid. Scientists traced the trajectory of the Chelyabinsk impactor backward into space and found consistent matches to asteroids 2007 BD7 and 2011 EO40 . One may be the parent body, but it remains uncertain.
An analysis of Chelyabinsk, together with smaller, lower-energy events, showed that these kinds of impactors affect us much more frequently than previously thought . A Chelyabinsk-size impact happens every 25 years or so, with most occurring over the ocean or wilderness areas, thankfully.
It's a bit alarming that astronomers didn't see this asteroid coming long before it hit us. But asteroids tend to be very dark, and small ones are extremely faint even when close to our planet. Just a few years earlier the four-meter-wide asteroid 2008 TC3 became the first one ever detected before striking Earth. Only six others have been discovered before impact since then, including 2023 CX1, which lit up the English Channel on February 13, 2023, as if marking the week's anniversary. All were small, posing no danger to us on the ground.
Now, after I've terrified you about impacts from these objects, comes the good news: we're getting much better at finding them. In the decade since Chelyabinsk, about 20,000 near-Earth asteroids have been discovered —more than had been found in all of history up to 2013. New survey telescopes such as Pan-STARRS and the Zwicky Transient Facility have come online, and better detection and analysis techniques have been developed that accelerated the rate of discovery. Soon the huge Vera Rubin Observatory and NASA's NEO Surveyor space mission will also significantly boost the number of known Earth-threatening asteroids.
Finding them, though, is just the first step . Doing something about them is the next. To that end, in November 2021 NASA launched the Double Asteroid Redirection Test (DART) mission, which slammed a half-ton impactor into the 170-meter-wide asteroid Dimorphos—a moon of the larger asteroid Didymos. The momentum from the collision changed the orbital period of the asteroid by more than half an hour . That was an even bigger shift than had been predicted—a vast plume of material that the impact excavated and flung away from the asteroid's surface added a kick—showing that it's possible to use such a spacecraft to alter an asteroid's trajectory.
Bigger blasts might be able to divert an incoming space rock as well. Detonating a nuclear weapon near a small asteroid could vaporize much of its surface. This hot vapor would rapidly expand, acting like rocket exhaust and pushing the asteroid into a new and, one hopes, safer trajectory. Some issues regarding this method are still fairly difficult to overcome— it's currently illegal under the Outer Space Treaty to explode nuclear devices in space, for example —but a dangerous asteroid headed our way might grease the skids a bit on a political fix.
Since the Chelyabinsk impact, two spacecraft have not only approached small asteroids but also collected samples from them; one, Hayabusa2, already dropped off its samples back at Earth, and the other, OSIRIS-REx, will do so later this year. Both asteroids, Ryugu (roughly one kilometer across) and Bennu (500 meters across), are essentially rubble piles, loose collections of small rocks held together by their own meager gravity. It's likely all small asteroids are rubble piles, which will affect how we fend them off; their weak structures mean they can absorb the impact of a spacecraft more easily. Imagine trying to punch a box of packing peanuts, and you'll get the idea. The DART mission showed, however, that copious amounts of material are ejected after a collision, and that transfer of momentum can actually increase the effect of an impact .
Chelyabinsk caught us by surprise, and although such small impacts may still sneak past our guard, we're getting better at finding potential threats from space and learning what we can do if we find one with Earth in its crosshairs. Big, dangerous asteroids are rare, yet we need only look to Meteor Crater in Arizona to see why we need to take them seriously. The explosion from that impact, estimated as 10 to 40 megatons, carved a hole more than a kilometer across in the desert about 50,000 years ago, probably devastating the plants and animals living there at the time . This might be one of the most recent large direct impacts Earth has suffered, but it won't be the last.
Unless, of course, we do something to stop them.
This is an opinion and analysis article, and the views expressed by the author or authors are not necessarily those of Scientific American.
Remembering the Chelyabinsk Impact 10 Years Ago, and Looking to the Future
On Feb. 15, 2013, the people of Chelyabinsk, Russia, experienced a shocking event, and yet it was a small fraction of the devastation an asteroid on a collision course with Earth could yield. As NASA’s Planetary Defense experts reflect on the Chelyabinsk impact 10 years ago, they also look forward to the future and all that the agency has since accomplished in the field of Planetary Defense.
Harmless meteoroids, and sometimes small asteroids, impact our planet’s atmosphere daily. When they do, they disintegrate and create meteors or “shooting stars” and sometimes bright fireballs or bolides. Such was the case on Feb. 12 when a very small asteroid impacted Earth’s atmosphere over Northern France soon after discovery, resulting in a spectacular light show for local onlookers. Much more rarely, a larger asteroid that is still too small to reach the ground intact, yet large enough to release considerable energy when it disintegrates, can do significant damage to the ground. On Feb. 15, 2013, one such bolide event garnered international attention when a house-sized asteroid impacted Earth’s atmosphere over Chelyabinsk, Russia, at a speed of eleven miles per second and exploded 14 miles above the ground. The explosion was equivalent to 440,000 tons of TNT, and the resulting air blast blew out windows over 200 square miles, damaged buildings, and injured over 1,600 people – mostly due to broken glass. Due to the asteroid’s approach from the daytime sky, it was not detected prior to impact, serving as a reminder that while there are no known asteroid threats to Earth for the next century, an Earth impact by an unknown asteroid could occur at any time.
Coincidentally, negotiations sponsored by the United Nations were finalizing formal recommendations for the establishment of Planetary Defense-related international collaborations – the International Asteroid Warning Network (IAWN) and the Space Missions Planning Advisory Group (SMPAG) – when the Chelyabinsk impact occurred. Since then, NASA established the agency’s Planetary Defense Coordination Office (PDCO) in 2016 to oversee and coordinate the agency’s ongoing mission of Planetary Defense. This includes acting as a national representative at international Planetary Defense-related caucuses and forums, such as IAWN and SMPAG, and playing a leading role in coordinating U.S. government planning for response to an actual asteroid impact threat if one were ever discovered. The PDCO also funds observatories around the world through NASA’s Near-Earth Object (NEO) Observations Program to find and characterize NEOs – asteroids and comets that come within 30 million miles of Earth – with a particular focus on finding asteroids 460 feet (140 meters) and larger that represent the most severe impact risks to Earth. To help accelerate its ability to find potentially hazardous NEOs, NASA is also actively developing the agency’s NEO Surveyor mission , which is designed to finish discovery of 90 percent of asteroids 140 meters in size or larger that can come near Earth within a decade of being launched.
In 2022, working together with the Italian Space Agency, NASA’s Double Asteroid Redirection Test (DART) mission successfully demonstrated the world’s first-ever test for deflecting an asteroid’s orbit. Launched in 2021 , DART successfully collided with a known asteroid – which posed no impact threat to Earth – demonstrating one method of asteroid deflection technology using a kinetic impactor spacecraft. Since DART’s impact, Planetary Defense experts have been continuing to analyze data returned from the mission to better understand its demonstrated effects on the asteroid, which contributes to the understanding of how a kinetic impactor spacecraft could be used to address an asteroid impact threat in the future if the need ever arose.
The Chelyabinsk impact was a spark that ignited global conversation in Planetary Defense, and much progress in the field has occurred since then. However, there is still more work to be done, and NASA is actively at the forefront. In addition to building NASA’s NEO Surveyor to find the rest of the population of asteroids that could pose a hazard to Earth, the agency is considering a “rapid response reconnaissance” capability to be able to quickly obtain a more detailed characterization of a hazardous asteroid once it is discovered. NASA is also considering sending out a reconnaissance spacecraft to study an asteroid making a close approach to Earth in 2029.
“A collision of a NEO with Earth is the only natural disaster we now know how humanity could completely prevent” said NASA Planetary Defense Officer Lindley Johnson. “We must keep searching for what we know is still out there, and we must continue to research and test Planetary Defense technologies and capabilities that could one day protect our planet’s inhabitants from a devastating event.”
Learn more about NASA’s Planetary Defense Coordination Office
Keep up to date on NASA’s Planetary Defense efforts by following Asteroid Watch on twitter
- Five Years after the Chelyabinsk Meteor: NASA Leads Efforts in Planetary Defense
- Around the World in Four Days: NASA Tracks Chelyabinsk Meteor Plume
- Science Papers on Chelyabinsk Meteor Findings