<p>That doesnt seem realistic since eventually all the dust from all the volcanic activity, as well as that caused by our doing, eventually makes its way back down to earth. Most dust particles end up being soaked up by earths cloud layer coming down in rain. I have to agree with Gimelist but volcanism can and has produced conditions you mentioned by expelling caustic and poisonous gases and for what I understand nuclear detonations and the radioactive dust they send into the air is far worse in the long run.</p>

CC BY-SA 4.0
2018-12-02T20:26:58.817Z
Another point is that earth's dynamic and ever changing weather keeps air circulating and not in one area.
Armondo Villaescuza
CC BY-SA 4.0
2018-12-02T20:22:54.650Z
2018-12-02T20:22:54.650Z
Armondo Villaescuza
<p>Dust would not have to be chemically poisonous to render air unbreathable but a big impact would first of all release a blast of hot plasma that nothing nearby will survive with accompanying air blast. Dust would be mostly from Earth material and that will vary in chemistry according to what is locally present; the <a href="https://www.lpi.usra.edu/science/kring/Chicxulub/global-effects/" rel="nofollow noreferrer">Chicxulub</a> (dinosaur killer) impact hit where abundant calcium sulphate minerals were present and those were thought to have caused acid rain (as well as releasing a lot of CO2 that, along with massive wildfires, caused later global warming). I suspect those kinds of dusts at high levels would be poisonous but the heat alone from material thrown into the air and lower space was thought to cause spontaneous wildfires over large areas around the planet - making the dust superfluous for rendering air unbreathable.</p>

CC BY-SA 4.0
2020-05-28T04:21:55.003Z
2020-05-28T04:21:55.003Z
Ken Fabian
<p><strong>tl;dr</strong> while the docudrama is over-dramatised, yes, this is possible.</p>

<p>Simply put, we already have processes which do make air unbreathable in small or even large areas, from dust or poisonous gases.</p>

<p>Typically these are volcanic in origin, with fine dust from some volcanoes causing breathing difficulties across large areas, and from gases (often sulphur-based) burning lung surfaces or excluding oxygen.</p>

<p>Impact from a large body can definitely have outcomes in related areas - dust or gas output, and while the immediate impact has more of a destruction aspect, once that has passed, gas and dust can very much be an ongoing problem, possibly even a semi-permanent issue, if the impact opens up new volcanic activity along a fault.</p>

CC BY-SA 4.0
2019-05-03T14:57:19.587Z
2019-05-03T14:57:19.587Z
Rory Alsop
<p>Disclaimer: I haven't watched the docudrama.</p>

<p>For a comet impact, I think the <em>chemical</em> effects (dumping poisonous gases into the atmosphere) would be completely overwhelmed by the <em>thermal</em> effects (lots and lots of kinetic energy converted to heat).</p>

<p>Those poisonous gases would surely be converted to plasma and/or blasted out in the shockwave from the impact. Any that were still solid at the point of ground impact would be splashed out in all directions, where they would quickly mix into the (suddenly superheated) atmosphere. Carbon monoxide, methane, and ammonia could burn <em>once they COOLED enough</em> to combine with atmospheric oxygen, but they'd already be diluted below toxic levels.</p>

<p>The heat from the impact would also cause all these products to rise into the stratosphere as a giant mushroom cloud, <em>drawing in fresh air</em> at its base.</p>

<p>So, no, I don't see how this could be realistic. I'm <em>almost</em> tempted to go look for the video to see just how bad it was... but not quite.</p>

CC BY-SA 4.0
2020-06-28T04:26:55.257Z
its actually really easier, molten rock turns into ultra-fine ash as is falls through the air, and it will fall back all around the impact site, and breathing in even relatively small amounts will destroy a set of lungs (it either fills it with mud or lacerates to to shreds or both), we see it with volcanoes. All long as the planet is still there you will have an ash fall around the impact site.
John
CC BY-SA 4.0
2019-05-02T19:12:41.857Z
2019-05-02T19:12:41.857Z
jeffB
<p>In the docudrama Super Comet After the Impact, the impact is shown to have made the air within a few miles of it unbreathable, and humans need gas masks to breath in this area.
How realistic is this?</p>

<p>I was told to come here after originally posting on the space stack.</p>

CC BY-SA 4.0
2018-12-01T20:00:38.237Z
Need more specifics on the size of the impact.  If it's big enough to penetrate down to the mantle, you might get a lot of CO2, SO2, and H2S, as with volcanic eruptions.  But of course if you were anywhere close, breathing is no longer an option :-)
jamesqf
CC BY-SA 4.0
2018-12-01T20:15:15.177Z
I call those programs "mockmentaries" ; in that they mock reality.
blacksmith37
CC BY-SA 4.0
2018-12-02T00:13:16.997Z
@jamesqf impacts doesn't get as deep as the mantle. Excavating several kilometres of crust by an impact is wishful thinking. However, this could trigger mantle activity indirectly. Furthermore, the carbon and sulfur gases would probably come from the upper crust, not the mantle.
Gimelist
CC BY-SA 4.0
2019-01-06T03:56:01.593Z
for how long is it unbreathable?
John
CC BY-SA 4.0
2019-05-03T04:53:59.170Z
Anything big enough to be called a "Super Comet" would fry anyone within a few miles of it (The Chelyabinsk meteor gave people sunburns).
Keith McClary
CC BY-SA 4.0
2020-01-29T10:09:33.647Z
This never got any terribly good answers. It seems to me that any chemical effects might persist for some time after the themal effects have subsided, hence there's scope.
Semidiurnal Simon
<atmosphere><climate><human-influence><impacts>
Could dust blown up by a comet impact render the air unbreathable?
Bella Barbiero
# Could dust blown up by a comet impact render the air unbreathable?

(Asked by: username_0 on 2018-12-01)

In the docudrama Super Comet After the Impact, the impact is shown to have made the air within a few miles of it unbreathable, and humans need gas masks to breath in this area.
How realistic is this?

I was told to come here after originally posting on the space stack.

**Tags:** atmosphere, climate, human-influence, impacts

> **Comments:**
> **username_1**: Need more specifics on the size of the impact.  If it's big enough to penetrate down to the mantle, you might get a lot of CO2, SO2, and H2S, as with volcanic eruptions.  But of course if you were anywhere close, breathing is no longer an option :-)  
> **username_2**: I call those programs "mockmentaries" ; in that they mock reality.  
> **username_3**: @username_1 impacts doesn't get as deep as the mantle. Excavating several kilometres of crust by an impact is wishful thinking. However, this could trigger mantle activity indirectly. Furthermore, the carbon and sulfur gases would probably come from the upper crust, not the mantle.  
> **username_4**: for how long is it unbreathable?  
> **username_5**: Anything big enough to be called a "Super Comet" would fry anyone within a few miles of it (The Chelyabinsk meteor gave people sunburns).  
> **username_6**: This never got any terribly good answers. It seems to me that any chemical effects might persist for some time after the themal effects have subsided, hence there's scope.  

---

## 4 answers

### Answer by username_7 on 2018-12-02. Score: 1

That doesnt seem realistic since eventually all the dust from all the volcanic activity, as well as that caused by our doing, eventually makes its way back down to earth. Most dust particles end up being soaked up by earths cloud layer coming down in rain. I have to agree with username_3 but volcanism can and has produced conditions you mentioned by expelling caustic and poisonous gases and for what I understand nuclear detonations and the radioactive dust they send into the air is far worse in the long run.

> **Comments:**
> **username_7**: Another point is that earth's dynamic and ever changing weather keeps air circulating and not in one area.  

---

### Answer by username_8 on 2020-05-28. Score: 1

Dust would not have to be chemically poisonous to render air unbreathable but a big impact would first of all release a blast of hot plasma that nothing nearby will survive with accompanying air blast. Dust would be mostly from Earth material and that will vary in chemistry according to what is locally present; the [Chicxulub](https://www.lpi.usra.edu/science/kring/Chicxulub/global-effects/) (dinosaur killer) impact hit where abundant calcium sulphate minerals were present and those were thought to have caused acid rain (as well as releasing a lot of CO2 that, along with massive wildfires, caused later global warming). I suspect those kinds of dusts at high levels would be poisonous but the heat alone from material thrown into the air and lower space was thought to cause spontaneous wildfires over large areas around the planet - making the dust superfluous for rendering air unbreathable.


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### Answer by username_9 on 2019-05-03. Score: 1

**tl;dr** while the docudrama is over-dramatised, yes, this is possible.

Simply put, we already have processes which do make air unbreathable in small or even large areas, from dust or poisonous gases.

Typically these are volcanic in origin, with fine dust from some volcanoes causing breathing difficulties across large areas, and from gases (often sulphur-based) burning lung surfaces or excluding oxygen.

Impact from a large body can definitely have outcomes in related areas - dust or gas output, and while the immediate impact has more of a destruction aspect, once that has passed, gas and dust can very much be an ongoing problem, possibly even a semi-permanent issue, if the impact opens up new volcanic activity along a fault.


---

### Answer by username_10 on 2019-05-02. Score: 1

Disclaimer: I haven't watched the docudrama.

For a comet impact, I think the *chemical* effects (dumping poisonous gases into the atmosphere) would be completely overwhelmed by the *thermal* effects (lots and lots of kinetic energy converted to heat).

Those poisonous gases would surely be converted to plasma and/or blasted out in the shockwave from the impact. Any that were still solid at the point of ground impact would be splashed out in all directions, where they would quickly mix into the (suddenly superheated) atmosphere. Carbon monoxide, methane, and ammonia could burn *once they COOLED enough* to combine with atmospheric oxygen, but they'd already be diluted below toxic levels.

The heat from the impact would also cause all these products to rise into the stratosphere as a giant mushroom cloud, *drawing in fresh air* at its base.

So, no, I don't see how this could be realistic. I'm *almost* tempted to go look for the video to see just how bad it was... but not quite.

> **Comments:**
> **username_4**: its actually really easier, molten rock turns into ultra-fine ash as is falls through the air, and it will fall back all around the impact site, and breathing in even relatively small amounts will destroy a set of lungs (it either fills it with mud or lacerates to to shreds or both), we see it with volcanoes. All long as the planet is still there you will have an ash fall around the impact site.  

---

