A huge fireball exploded in Earth's atmosphere in December, according to Nasa | Hacker News Reader

A huge fireball exploded in Earth's atmosphere in December, according to Nasa

bbc.com

214 pointsokket78 comments

This one was detected by satellite, but scientists have been using acoustic detection of meteorite explosions for some time. Fittingly, they used detectors made for nuclear explosions, the Comprehensive Test Ban Treaty Organization's infrasound network [1].

I learned this from reading this highly recommended book on the subject: Asteroids: Relics of Ancient Time by Michael K. Shepard [2] (amazon link)

[1] https://www.norsar.no/r-d/safe-society/nuclear-test-ban-moni...

[2] https://www.amazon.com/reader/110706144X?_encoding=UTF8&quer...

Vela Incident https://en.wikipedia.org/wiki/Vela_Incident

Also: "Imagine what might have happened if this meteor had exploded not over the Bering Sea but over nuclear-armed North Korea, India, or Pakistan during a time of increased tensions or actual conflict."

https://twitter.com/AtomicAnalyst/status/1107660418967916545

A similar situation happened in 2002 during a time of Indian-Pakistani tensions. https://en.wikipedia.org/wiki/2002_Eastern_Mediterranean_eve...

Chelyabinsk meteor exploded almost over a city:

"The first explosion was the most powerful, and was preceded by a bright flash, which lasted about five seconds. Initial newspaper altitude estimates ranged from 30–70 km, with an explosive equivalent, according to NASA, of roughly 500 kilotonnes of TNT (2,100 TJ), although there is some debate on this yield (500 kt is exactly the same energy released by the Ivy King nuclear explosion in 1952). According to a paper in 2013, all these ~500 kiloton yield estimates for the meteor airburst are "uncertain by a factor of two because of a lack of calibration data at those high energies and altitudes."

The hypocentre of the explosion was to the south of Chelyabinsk, in Yemanzhelinsk and Yuzhnouralsk. Due to the height of the air burst, the atmosphere absorbed most of the explosion's energy."

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

I mean, with all the money the US currently spends on military budgets, I can't for the life of me figure out why it is so hard to find the 50-100mil or so (estimated) it would cost for a few orbital IR telescopes and just deal with this problem once and for all.

A Pegasus XL rocket can lift 976 pounds (443 kilograms) into low-Earth orbit for about $13.5 million...put two "budget" telescopes on one launch and get to work.

It is expected to happen only about 3 times in a century (from article).

In other words, building this system of telescopes won't affect the next elections in any positive way.

NASA actually receive lots of funding(might be second after military). Most of their work doesn't align with any of the politics promises, even then they receive good chunk of budget spending.

In the end, it's always about politics:

https://en.wikipedia.org/wiki/Budget_of_NASA#Political_oppos...

Isn’t everything?

NASA 2018 budget is $20.7B. It is not in any way "second after military".

NIH 2018 budget is $37B, NSF is $7.8B. DOD budget just for R&D and test/evaluation is $88B.

So, 3rd behind military and NIH then?

No, no, no. I just picked a couple of numbers of relevant research-related agencies as a general comparative. ("This is is the kind of league NASA is in.") Other comparatives might be DOE, NOAA, USGS, NIST.

The federal budget is about $4000B. Discretionary spending is about $1200B. NASA is so far down in the noise of this that it's not funny (20B/1200B ~ 1.7%).

As an example, Federal highway spending (not state) is $44B.

Health and Human Services was $1.7 Trillion, Social Security was $1.1 Trillion, Defense was $1.1 Trillion, NASA is pretty far down the list (~19th), at $24 Billion, .35% of budget:

https://www.usaspending.gov/#/explorer/agency

At least there is the benefit of DOD tech trickling down to NASA tech at some point.

Everyone else likely missed it, but I want you to know I appreciate this joke.

> Everyone else likely missed it

I’m sure you’re the only one to notice the obvious joke.

Sure it's a joke?

These already exist. My old boss ran space command at NORAD at the end of the Cold War. Their problem wasn’t capturing the data but filtering it out when looking for artificial events. Unfortunately this data isn’t being collected and used by the civilian sector which is a crying shame.

My old boss ran space command at NORAD at the end of the Cold War.

That’s amazing. You should tell us everything.

There are plenty of satellites out there that monitor for missile launches using IR cameras. These might detecting all of these meteor explosions and the military is not reporting them due to not wanting their operational capacity being known. The previous generation of missile detection missiles could see Scud launches during Desert Storm in 1991. I'm sure the military sees all kinds of weird space stuff and doesn't mention a word.

Latest generation: https://en.wikipedia.org/wiki/Space-Based_Infrared_System

Yep, they sent satellites to the moon in 1968 ahead of the Apollo mission. They had to noise the images they took so the world wouldn't know precisely their level of capability, but the photos taken of the entire moon had super high, crisp resolution.

>but the photos taken of the entire moon had super high, crisp resolution.

At the time, wouldn't they be film based images? If so, well, obviously the resolution would be high and crisp, especially if it was medium/large format.

These images were developed, digitized, compressed, and transmitted back to NASA from the Lunar orbiters. This article has the story of how they were recovered recently.

https://boingboing.net/2018/06/16/ampex-fr-900-drives.html

A study team looked at space-based and ground-based visible and IR options. Their 2017 report is: https://cneos.jpl.nasa.gov/doc/2017_neo_sdt_final_e-version.... (long PDF)

The cost estimate for development, launch, and operations varies a lot, but is in the $0.8-$2.0B range. See the cost roll-up on page 163 of the above document. It's ~0.5-1.0 meter telescope, and detector cooling and data rates are an issue.

The scientist quoted in the above article, Amy Mainzer, is leading a more detailed study which is among a handful of proposal concepts (not all NEO-related) that NASA will select from.

It's possible that in 1178 an asteroid hit the Moon with a 120,000 megaton blast - an Extinction Event if it had hit the Earth.

(By way of comparison, the Hiroshima Bomb was 15 kilotons).

Recorded by monks at Canterbury at the time, and only a possibility - but something to consider.

https://en.wikipedia.org/wiki/Giordano_Bruno_(crater)

According to the same page, more recent developments don't support the theory:

> High-resolution images obtained by the Japanese satellite SELENE in 2008 were used to date the crater by counting the smaller craters within it and its ejecta deposits. This gave an age of 4(+6, −3) million years, much too old for the hypothesis.[2]

> This raises the question of what the monks saw. An alternative theory holds that the monks just happened to be in the right place at the right time to see an exploding meteor coming at them and aligned with the Moon. This would explain why the monks were the only people known to have witnessed the event; such an alignment would only be observable from a specific spot on the Earth's surface.[8]

What the monks reported sounds like it might be consistent with the optical disturbances caused by superheated air:

> From the midpoint of the division a flaming torch sprang up, spewing out, over a considerable distance, fire, hot coals and sparks. Meanwhile the body of the Moon which was below writhed, as it were in anxiety, and to put it in the words of those who reported it to me and saw it with their own eyes, the Moon throbbed like a wounded snake. Afterwards it resumed its proper state. This phenomenon was repeated a dozen times or more, the flame assuming various twisting shapes at random and then returning to normal. Then, after these transformations, the Moon from horn to horn, that is along its whole length, took on a blackish appearance.

An air burst between observer and observed would move around on the wind, causing ripples to come and go.

> An air burst between observer and observed would move around on the wind, causing ripples to come and go.

Agreed. Far more likely that an impact causing the moon to wobble or visibly move, which would have to be an obscenely destructive impact.

That's 120 Gigaton. That's enormous and would probably have debris flying around for quite a while. I am pretty sure some other people would have noticed that too.

Assuming we (Earth) get some reasonable warning time for a problematic impact, the logistics of alerting -and then moving- a large metropolitan area like NYC, for example, are interesting. Where do we place these people? What about the city's infrastructure? Do we just stand by, brace for impact and hope for the best? Or is there something more we could do to mitigate the disaster? I know a lot of that depends on the amount of time beforehand, but I find the problem intriguing.

see how evacuations before large hurricanes or other predictable disasters are going. It's problematic at best.

Those don't serve as good examples since e.g. for hurricanes by the time the evacuation order is given the weather itself is causing issues for the evacuation.

It would still be a logistical nightmare, but other things being equal should proceed in a more orderly fashion than a hurricane evacuation, especially since the exact time of impact would be known in advance.

They do serve as a good indicator. The primary problems that occur during evacuations are "people don't believe it will hit them" and "there's no way to move all those people." I'd also doubt that our math is good enough to precisely calculate the impact point of a meteorite more than few days in advance. Hit/no-hit probably, and which region, yes, but off by 50km? Meteorites break up on atmospheric impact, getting the precise point right is probably impossible.

You may be interested in a recent episode of the 99 Percent Invisible podcast (https://99percentinvisible.org/episode/atomic-tattoos/). The title of the podcast comes from a Cold War program carried out in 1952 in which students could opt to receive a small tattoo of their blood type, with the goal of creating a "walking blood bank" in the event of a disaster requiring mass transfusions.

Related to your question, the episode also explores the history of "duck and cover." It turns out it's there is some credibility to the technique. In September 1945, the US sent a team called the Atomic Bomb Casualty Commission to Japan to research and interview survivors of nuclear blasts. They located survivors just a few blocks from the explosion epicenter, who had been sheltered by concrete basements. They also heard stories of people who were killed just by shattering windows and falling debris. With just some ability to shelter, survivability might be higher than you suspect.

That's really interesting, for itself and other reasons. The US sending a commission into Japan (in '45!) for the sole purpose of studying survivability related to atomic blasts seems sort of mind-blowing to me.

Thank you for the podcast reference.

We had a recent example of the value of "duck and cover" - and more specifically what happens if you don't do it - the Chelyabinsk meteor.

"Its explosion created panic among local residents, and about 1,500 people were injured seriously enough to seek medical treatment. All of the injuries were due to indirect effects rather than the meteor itself, mainly from broken glass from windows that were blown in when the shock wave arrived, minutes after the superbolide's flash."

Many of the injured went to a window to see the spectacle in the sky, not realizing that the shock wave was about to shatter the window in their face.

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

>Many of the injured went to a window to see the spectacle in the sky, not realizing that the shock wave was about to shatter the window in their face.

Same thing happened in the Halifax explosion.

That explosion was close enough that there would be basically no chance to react between the actual explosion and the shock wave.

And from that article, there's even a way to compare the effects of duck & cover:

"A fourth-grade teacher in Chelyabinsk, Yulia Karbysheva, was hailed as a hero after saving 44 children from imploding window glass cuts. Despite not knowing the origin of the intense flash of light, Karbysheva thought it prudent to take precautionary measures by ordering her students to stay away from the room's windows and to perform a duck and cover maneuver and then to leave a building. Karbysheva, who remained standing, was seriously lacerated when the blast arrived and window glass severed a tendon in one of her arms and left thigh; none of her students, whom she ordered to hide under their desks, suffered cuts."

Back in elementary school, we practiced duck-and-cover not as a defense against nuclear war (although we were only a couple of kilotons from the DoE Pantex plant), but against tornadoes. They're not entirely different, effectwise.

The earth is rotating so fast. You’d need really precise timing to know where it would hit.

we can account for a nanosecond discrepancy in the flow of time between two objects separated by hundreds of miles. IE: accounting for reletivity to sync time between phones and satellites. We have the technology.

> Measuring several metres in size, the space rock exploded 25.6km above the Earth's surface, with an impact energy of 173 kilotons.

What causes a meteor to explode 25km above the earth? Thermal expansion of internal gas?

It's called an explosion, but it's more of a conversion of kinetic energy to heat due to friction against the air. As the rock heats up, it starts to fall apart, and then smaller pieces go through that as well.

Here's a neat simulation of the process:

https://www.youtube.com/watch?v=tbh6GjRChnQ

Isn't it more about air compression instead of friction ?

Correct. Further reading: https://www.quora.com/Why-does-a-spacecraft-heat-up-during-r...

Mainly aerodynamic forces.

The heating event is so quick there's not time for the interior of a sizable meteor to warm up. Meteors' thermal conductivity and diffusivity are generally pretty low.

Even at 25km altitude, aerodynamic forces are very high and nonuniform with shock wave impingements. These forces will shatter a rocky meteor quite suddenly.

Well this is terrifying. Time to call in the Space Force!

To justify the costs of Space Force, First, we need to find space terrorists. Or, find aliens and sell weapons to them.

There's oil on Titan!

(No, really, there is!)

Do any of these asteroids have oil?

> The space rock exploded with 10 times the energy released by the Hiroshima atomic bomb

Well, that's fun.

Kinetic energy is a hell of a thing. That squared term really adds up quick

Yeah. It's O(n^2). Should optimize.

Can you elaborate plz?

The energy of an object is (1/2)mv^2. Doubling velocity quadruples the kinetic energy.

Kinetic energy is 1/2mv^2

How many Library of Congresses is that?

10x Hiroshima is still solidly sub-megaton. We dropped a lot of megaton bombs on the middle of nowhere before atmospheric testing was banned.

Why does the BBC not use the NASA acronym?

Certain languages (British English and Portuguese, to name the two I know) dictate that if you pronounce the acronym as if it were a word, you only capitalize the first letter.

Nasa and Nato, but NSA and WTO.

And in the US, non-proper nouns are often all lowercase even if they were originally acronyms. e.g. radar, laser, sonar, etc. And, even for proper nouns, things like programming languages often just has an initial cap although all caps is typically the technically correct form in US English.

Example reference: see the "abbreviations and acronyms" section in: https://www.theguardian.com/guardian-observer-style-guide-a

Hilariously enough, "Nasa" is specifically called out as an negative example from the English Wikipedia style guidelines: https://en.wikipedia.org/wiki/Wikipedia:Manual_of_Style/Capi...

Doesn't the BBC still believe in a country called "Burma"?

While I was working at NASA I was told by a colleague that Trump canceled the asteroid deflection program that was being ran at the LaRC facility. Now looking for a reference all I can find is news about him starting an asteroid deflection program because of this incident.

I'm not sure of the details since I was working in an AI research department.

Here you go. That was news from a budget proposal on March 16, 2017

https://www.space.com/36090-trump-2018-nasa-budget-request.h...

I mean, that's not how the US budget works. But yes, his budget proposal included nixing an Obama-era project to redirect an asteroid to lunar space for a manned mission. I wouldn't call that a deflection program.

I'd say deflecting an asteroid so that it goes closer to Earth still counts as deflecting :) That said, the cancellation was a shame since it gave the Lunar Gateway a concrete and useful purpose.

Lindley Johnson, planetary defence officer at Nasa, told BBC News a fireball this big is only expected about two or three times every 100 years.

Best title ever.

Oh hell yes.

Can't compete with that guys job title at the class reunion.

Well, there's also a "planetary protection officer", Lisa Pratt (and deputy planetary protection officer Elaine Seasly) :-)

There was also this 9 years old kid who applied for planetary protection officer position :)

https://www.businessinsider.de/child-applies-nasa-planetary-...

That was my take from the article too. Hell of a job title

The gods are angry

"That's another thing we have in our defence, there's plenty of water on the planet."

so that's what planetary defence people do :D since it's unrealistic to prepare to defend the planet actually, let's just point at things :D and call them out for being in our defence! :D we have mountains too! they are also in our defence!

Womp womp, article didn't get picked up when I posted it last night. Guess I should have retitled / waited until morning!

https://news.ycombinator.com/item?id=19418939

Reply on news.ycombinator.com