<p>Yes, comets can and do become extinct. It likely depends on the initial size of their nucleus.</p>
<p>The defining property of a comet is that it can develop a gas and dust tail in the vicinity of the Sun - thus it needs to have enough volatile material which can still evaporate.</p>
<p>Depending on the size and composition this process may find an end when the volatile material at the surface is all gone and the evaporation is not strong enough any longer to drag along any dust which forms the visible tail.</p>
<p><a href="https://www.aanda.org/articles/aa/pdf/2016/05/aa27260-15.pdf" rel="noreferrer">Gundlach and collegues</a> made lab experiments, calculations and comparisons with the in-situe measurements by the Rosetta spacecraft and found that this may depend on the size of the comet's nucleus: for larger bodies it needs a bigger pressure to overcome gravity and tensile strength of the surface material. Thus it is harder to drag along further dust - and they form quicker an inactive surface layer.</p>
<p>In the figure taken from their work you see the tensile strength of the typical material due to compression of its own gravity for bodies of the size indicated. <a href="https://i.sstatic.net/AJB6D0Z8.png" rel="noreferrer"><img src="https://i.sstatic.net/AJB6D0Z8.png" alt="Tensile strength of dust pebbles compressed by gravity" /></a>. The grey-shaded area indicates the typical tensile strength as measured in-situ by Rosetta on 67P/Churyumov-Gerasimenko.
It shows that from a 30km pristine comet you can erode a few 10m of surface as the lower layers are already compressed to a too high tensile strength to be eroded away by comet activity. These body will then eventually be known as extinct comet or 'asteroid in cometary orbit' (ACO). However a body of only 1km is small enough and has low enough gravity that it might completely evaporate over time when it nears the Sun repeatedly (<a href="https://www.esa.int/ESA_Multimedia/Images/2024/04/Rare_sighting_of_doomed_SOHO_comet_during_solar_eclipse" rel="noreferrer">this has e.g. been observed by SoHo</a>).</p>
<p>Mind though, that such an extinct comet might still have water below the surface: The heat conductivity of the material is very low. Thus the heat does not penetrate deep, and the resulting slight temperature variation at depth doesn't suffice then anymore for any significant amount of water or CO2 to evaporate or even lift-off any dust/rock/carbon grains from the surface. Thus the surface is all solid grains sticking to eachother, and a meter below this surface you still have the pristine material.</p>

CC BY-SA 4.0
2024-08-12T06:41:24.670Z
2024-08-12T08:05:46.567Z
2024-08-12T08:05:46.567Z
planetmaker
<p>As described in other answers, the answer is &quot;Yes; they then become (like) asteroids&quot;. This answer describes asteroids that appear to have been comets in their former days.</p>
<p>Such identifications must be provisional unless we were lucky and smart enough to have followed the object from the time it had ices and showed cometary activity. But certain orbital characteristics are suggestive of a cometary origin, and are shared by most apparent extinct comets:</p>
<ul>
<li><p>High eccentricity: objects that have permanently been asteroids follow less eccentric orbits; the extinct comets generally keep the more eccentric orbits typical of comets.</p>
</li>
<li><p>Close perihelion compared with most asteroids: this favors faster evaporation and exhaustion of the ices. Live fast, die young.</p>
</li>
</ul>
<p>We look at the perihelion (P), aphelion (A), and eccentricity (e) for the first four candidates listed in the <a href="https://en.wikipedia.org/wiki/Extinct_comet" rel="nofollow noreferrer">article</a> referenced by Nilay Ghosh. Data are from the respective Wikipedia articles for these comets; P and A are in astronomical units.</p>
<p><a href="https://en.wikipedia.org/wiki/(137924)_2000_BD19" rel="nofollow noreferrer">(137924) 2000 BD19</a>: P = 0.0921, A = 1.6609, e = 0.8950</p>
<p><a href="https://en.wikipedia.org/wiki/14827_Hypnos" rel="nofollow noreferrer">14827 Hypnos</a>: P = 0.9481, A = 4.7318, e = 0.6659</p>
<p><a href="https://en.wikipedia.org/wiki/2101_Adonis" rel="nofollow noreferrer">2101 Adonis</a>: P = 0.4414, A = 3.3069, e = 0.7644</p>
<p><a href="https://en.wikipedia.org/wiki/2101_Adonis" rel="nofollow noreferrer">2015 TB145</a>: P = 0.2941, A = 3.9073, e = 0.8600</p>

CC BY-SA 4.0
2024-08-14T23:50:13.833Z
2024-08-15T01:10:33.997Z
2024-08-15T01:10:33.997Z
Oscar Lanzi
<p>Sort of; once enough volatiles leave the surface, the leftover non volatile material acts as a barrier to prevent any further loss of volatiles, including water!</p>

CC BY-SA 4.0
2024-08-15T12:25:14.177Z
Why the downvotes
Harrychink
CC BY-SA 4.0
2024-08-15T15:46:58.547Z
I didn't downvote. But IMHO it's extremely brief, no references, and compared to the existing answers no new information and also not clearer... thus someone must have thought "This answer is not useful" as by the mouse-over tooltip?
planetmaker
CC BY-SA 4.0
2024-08-15T00:59:01.533Z
2024-08-15T00:59:01.533Z
Harrychink
<p>Yes. Its only logical, but the real corollary to this is the 'lie' that comets have precise orbital periods. They simply cannot because they lose mass over time. Haley was wrong.</p>

CC BY-SA 4.0
2024-08-16T08:22:05.953Z
Mass loss has virtually no effect on orbital period. Typically, ices on a heated comet are ejected symmetrically, and are then pushed away from the Sun by radiation pressure (and slightly by the solar wind). But that symmetrical mass loss doesn't affect the comet's velocity. Comet orbits are affected by close encounters with planets, though, and by solar radiation pressure. FWIW, JPL Horizons provides 30 separate files for Halley's comet, one for each of its recent approaches. https://ssd.jpl.nasa.gov/api/horizons.api?format=text&MAKE_EPHEM=NO&COMMAND=Halley
PM 2Ring
CC BY-SA 4.0
2024-08-16T09:04:49.987Z
Welcome to SE. This site lives from solid answers with preferentially references to support any claims. I suggest to focus on new questions (ok, like this) or older ones which don't yet have elaborate answers or where those are missing aspects. I can recommend to take a look at https://astronomy.stackexchange.com/help/how-to-answer
planetmaker
CC BY-SA 4.0
2024-08-16T13:45:37.347Z
Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer).
Community
CC BY-SA 4.0
2024-08-16T07:32:29.220Z
2024-08-16T07:32:29.220Z
Garvit
<p>Yes, they are called <a href="https://en.wikipedia.org/wiki/Extinct_comet" rel="noreferrer">Extinct comets</a>.</p>
<blockquote>
<p>The Jupiter Family comets are active over a lifetime of about 10,000 years or ~1,000 orbits whereas long-period comets fade much faster. Only 10% of the long-period comets survive more than 50 passages to small perihelion and only 1% of them survive more than 2,000 passages. <strong>Eventually most of the volatile material contained in a comet nucleus evaporates, and the comet becomes a small, dark, inert lump of rock or rubble that can resemble an asteroid.</strong> Some asteroids in elliptical orbits are now identified as extinct comets. Roughly six percent of the near-Earth asteroids are thought to be extinct comet nuclei.</p>
</blockquote>

CC BY-SA 4.0
2024-08-14T23:13:53.123Z
I was going to say the same thing, but the Wikipedia passage cites references. Usually I include these when quoting from WP. What say you?
Oscar Lanzi
CC BY-SA 4.0
2024-08-12T02:48:53.647Z
2024-08-12T02:48:53.647Z
Nilay Ghosh
<p>Does all the water eventually boil out of old or short period comets?</p>
<p>If so, do they then turn into asteroids?</p>
<p>Are there any?</p>

CC BY-SA 4.0
2024-08-11T16:57:52.363Z
Yes: https://science.nasa.gov/resource/dead-comet/
James K
CC BY-SA 4.0
2024-08-12T22:00:51.070Z
In addition to the two excellent answers, comets can also disintegrate, which, I guess, can be considered as “running out of water.”
Pierre Paquette
<comets>
Do comets ever run out of water?
Miss Understands
# Do comets ever run out of water?

(Asked by: username_0 on 2024-08-11)

Does all the water eventually boil out of old or short period comets?

If so, do they then turn into asteroids?

Are there any?

**Tags:** comets

> **Comments:**
> **username_1**: Yes: https://science.nasa.gov/resource/dead-comet/  
> **username_2**: In addition to the two excellent answers, comets can also disintegrate, which, I guess, can be considered as “running out of water.”  

---

## 5 answers

### Answer by username_9 on 2024-08-12. Score: 38 | Accepted answer

Yes, they are called [Extinct comets](https://en.wikipedia.org/wiki/Extinct_comet).

> The Jupiter Family comets are active over a lifetime of about 10,000 years or ~1,000 orbits whereas long-period comets fade much faster. Only 10% of the long-period comets survive more than 50 passages to small perihelion and only 1% of them survive more than 2,000 passages. **Eventually most of the volatile material contained in a comet nucleus evaporates, and the comet becomes a small, dark, inert lump of rock or rubble that can resemble an asteroid.** Some asteroids in elliptical orbits are now identified as extinct comets. Roughly six percent of the near-Earth asteroids are thought to be extinct comet nuclei.

> **Comments:**
> **username_4**: I was going to say the same thing, but the Wikipedia passage cites references. Usually I include these when quoting from WP. What say you?  

---

### Answer by username_3 on 2024-08-12. Score: 12

Yes, comets can and do become extinct. It likely depends on the initial size of their nucleus.

The defining property of a comet is that it can develop a gas and dust tail in the vicinity of the Sun - thus it needs to have enough volatile material which can still evaporate.

Depending on the size and composition this process may find an end when the volatile material at the surface is all gone and the evaporation is not strong enough any longer to drag along any dust which forms the visible tail.

[Gundlach and collegues](https://www.aanda.org/articles/aa/pdf/2016/05/aa27260-15.pdf) made lab experiments, calculations and comparisons with the in-situe measurements by the Rosetta spacecraft and found that this may depend on the size of the comet's nucleus: for larger bodies it needs a bigger pressure to overcome gravity and tensile strength of the surface material. Thus it is harder to drag along further dust - and they form quicker an inactive surface layer.

In the figure taken from their work you see the tensile strength of the typical material due to compression of its own gravity for bodies of the size indicated. [![Tensile strength of dust pebbles compressed by gravity](https://i.sstatic.net/AJB6D0Z8.png)](https://i.sstatic.net/AJB6D0Z8.png). The grey-shaded area indicates the typical tensile strength as measured in-situ by Rosetta on 67P/Churyumov-Gerasimenko.
It shows that from a 30km pristine comet you can erode a few 10m of surface as the lower layers are already compressed to a too high tensile strength to be eroded away by comet activity. These body will then eventually be known as extinct comet or 'asteroid in cometary orbit' (ACO). However a body of only 1km is small enough and has low enough gravity that it might completely evaporate over time when it nears the Sun repeatedly ([this has e.g. been observed by SoHo](https://www.esa.int/ESA_Multimedia/Images/2024/04/Rare_sighting_of_doomed_SOHO_comet_during_solar_eclipse)).

Mind though, that such an extinct comet might still have water below the surface: The heat conductivity of the material is very low. Thus the heat does not penetrate deep, and the resulting slight temperature variation at depth doesn't suffice then anymore for any significant amount of water or CO2 to evaporate or even lift-off any dust/rock/carbon grains from the surface. Thus the surface is all solid grains sticking to eachother, and a meter below this surface you still have the pristine material.


---

### Answer by username_4 on 2024-08-14. Score: 2

As described in other answers, the answer is "Yes; they then become (like) asteroids". This answer describes asteroids that appear to have been comets in their former days.

Such identifications must be provisional unless we were lucky and smart enough to have followed the object from the time it had ices and showed cometary activity. But certain orbital characteristics are suggestive of a cometary origin, and are shared by most apparent extinct comets:

* High eccentricity: objects that have permanently been asteroids follow less eccentric orbits; the extinct comets generally keep the more eccentric orbits typical of comets.
* Close perihelion compared with most asteroids: this favors faster evaporation and exhaustion of the ices. Live fast, die young.

We look at the perihelion (P), aphelion (A), and eccentricity (e) for the first four candidates listed in the [article](https://en.wikipedia.org/wiki/Extinct_comet) referenced by username_9 username_9. Data are from the respective Wikipedia articles for these comets; P and A are in astronomical units.

[(137924) 2000 BD19](https://en.wikipedia.org/wiki/(137924)_2000_BD19): P = 0.0921, A = 1.6609, e = 0.8950

[14827 Hypnos](https://en.wikipedia.org/wiki/14827_Hypnos): P = 0.9481, A = 4.7318, e = 0.6659

[2101 Adonis](https://en.wikipedia.org/wiki/2101_Adonis): P = 0.4414, A = 3.3069, e = 0.7644

[2015 TB145](https://en.wikipedia.org/wiki/2101_Adonis): P = 0.2941, A = 3.9073, e = 0.8600


---

### Answer by username_5 on 2024-08-15. Score: -2

Sort of; once enough volatiles leave the surface, the leftover non volatile material acts as a barrier to prevent any further loss of volatiles, including water!

> **Comments:**
> **username_5**: Why the downvotes  
> **username_3**: I didn't downvote. But IMHO it's extremely brief, no references, and compared to the existing answers no new information and also not clearer... thus someone must have thought "This answer is not useful" as by the mouse-over tooltip?  

---

### Answer by username_6 on 2024-08-16. Score: -5

Yes. Its only logical, but the real corollary to this is the 'lie' that comets have precise orbital periods. They simply cannot because they lose mass over time. Haley was wrong.

> **Comments:**
> **username_7**: Mass loss has virtually no effect on orbital period. Typically, ices on a heated comet are ejected symmetrically, and are then pushed away from the Sun by radiation pressure (and slightly by the solar wind). But that symmetrical mass loss doesn't affect the comet's velocity. Comet orbits are affected by close encounters with planets, though, and by solar radiation pressure. FWIW, JPL Horizons provides 30 separate files for Halley's comet, one for each of its recent approaches. https://ssd.jpl.nasa.gov/api/horizons.api?format=text&MAKE_EPHEM=NO&COMMAND=Halley  
> **username_3**: Welcome to SE. This site lives from solid answers with preferentially references to support any claims. I suggest to focus on new questions (ok, like this) or older ones which don't yet have elaborate answers or where those are missing aspects. I can recommend to take a look at https://astronomy.stackexchange.com/help/how-to-answer  
> **username_8**: Your answer could be improved with additional supporting information. Please [edit] to add further details, such as citations or documentation, so that others can confirm that your answer is correct. You can find more information on how to write good answers [in the help center](/help/how-to-answer).  

---

