<p>Dating the age of the asteroid belt is a problem that has to date no general solution. </p>

<p>Rocks are usually dated in the laboratory via <a href="https://en.wikipedia.org/wiki/Mass_spectrometry" rel="nofollow noreferrer">isotopical analysis</a>. This is possible for meteorites, but what to do about those rocks that remain in space?</p>

<p>Several methods to date the asteroid belt are known to me, apart from ad-hoc assumptions that it has the same age as the planets:</p>

<ol>
<li>Creating links between dated meteorites and asteroid families: The meteorite family of <a href="https://en.wikipedia.org/wiki/L_chondrite" rel="nofollow noreferrer">L chondrites</a> have possible origin families in the asteroid belt. Those 'families' are small <a href="https://en.wikipedia.org/wiki/Asteroid_family" rel="nofollow noreferrer">blobs in the eccentricity-inclination</a> diagrams, that probably originated in one common parent-body breakup event. Dating meteorites originating from those families, gives minimum ages for the parent bodies of i.e. 500 Myrs for the <a href="https://en.wikipedia.org/wiki/Ordovician_meteor_event" rel="nofollow noreferrer">Ordovician meteor event.</a></li>
<li>Dynamical age modeling: After a breakup of a parent body, the cloud of fragments experience different strengths of <a href="https://en.wikipedia.org/wiki/Yarkovsky%E2%80%93O%27Keefe%E2%80%93Radzievskii%E2%80%93Paddack_effect" rel="nofollow noreferrer">YORP</a> and tidal forces, which causes their semimajor axis distribution to spread. Taking a given distribution, one can <a href="https://www.sciencedirect.com/science/article/abs/pii/S0019103502968302" rel="nofollow noreferrer">calculate back</a> to an age of when the cloud was one particle, i.e. the moment of breakup. This again is a minimum age and found for the Flora family to be more than <span class="math-container">$10^8$</span>, but less than <span class="math-container">$10^9$</span> years. This does exclude a very young belt, but does not say much about the upper age limit.</li>
<li>Crater ages: For the largest bodies, i.e. Ceres, Vesta, etc. we can assign <a href="https://en.wikipedia.org/wiki/Crater_counting" rel="nofollow noreferrer">relative ages</a> to the lunar cataclysm. Those usually give ages in excess than 3-4 Gyrs. For bodies like Vesta, where the surface is saturated with craters, this age is a lower limit.</li>
<li>Dating of crustal ejecta: There is another family of meteorites that can be linked specifically to Vesta via spectroscopy, called the <a href="https://en.wikipedia.org/wiki/HED_meteorite" rel="nofollow noreferrer">HED meteorites</a>. Those meteorites look like they're coming from a differentiated parent body (melted, low siderophile element content), and they containt <a href="https://en.wikipedia.org/wiki/Calcium%E2%80%93aluminium-rich_inclusion" rel="nofollow noreferrer">CAIs</a>. Thus, we can date Vesta at least back to the origin of the solar system, as CAIs give us the effective <span class="math-container">$t0$</span> for the formation of the solar system.</li>
</ol>

CC BY-SA 4.0
2019-07-21T19:31:49.877Z
2019-07-21T22:34:33.290Z
2019-07-21T22:34:33.290Z
AtmosphericPrisonEscape
<p>Some of this, as you say, is crackpot stuff, but there have, long ago, been some major collisions in the asteroid belt. The asteroid belt was formed about the same time as the Earth, and these collisions took place quite early on, billions of years before there were any humans. Mars never passed close enough for humans to observe its moons until telescopes were invented, but it does come within 35 million miles on closest approach. Only Venus comes closer at a distance of 26 million miles. The only asteroid belt we can study is our own, but common sense tells us that there must be other solar systems with asteroid belts, created in much the same way as ours. Some of the fragments from these asteroid belt collisions have been propelled Earthwards and left many huge craters, but only the biggest from the last couple of billion years have left identifiable traces. Those from earlier times, especially those that fell in deep ocean, have been eroded and left no visible trace.</p>

CC BY-SA 4.0
2019-07-21T23:26:06.983Z
Some craters no doubt got subducted.
Wayfaring Stranger
CC BY-SA 4.0
2019-07-20T08:28:29.520Z
2019-07-20T08:28:29.520Z
Michael Walsby
<p>I heard a theory (possibly from a crackpot) that there was an event in our solar system where two objects collided and created the asteroid belt, the orbits of some of the planets were altered, and that this event took place late enough for homo sapiens to have referenced observations made during the previous orbit in their oral traditions. (Mars parsing close enough to Earth for people to observe its moons)</p>

<p>Is any of this possible given readily observable evidence?
Are asteroid belts ever created in this way?</p>

CC BY-SA 4.0
2019-07-20T23:26:09.630Z
I'm too tired right now, to write you an answer, but what you are asking for are the [Grand Tack](https://en.wikipedia.org/wiki/Grand_tack_hypothesis) and the [Nice model](https://en.wikipedia.org/wiki/Nice_model). The asteroid belt being created by a single collision, and Mars being close to earth are both bullshit.
jan.sende
CC BY-SA 4.0
2019-07-21T00:45:19.480Z
There's info online on the youngest earthly meteor shower. It's origin is millions of years ago IIRC, and it surely post-dates the asteroid belt. It is too hot to actually find anything on internet right now, sorry.
Wayfaring Stranger
CC BY-SA 4.0
2019-07-23T10:22:03.627Z
[This answer by zephyr](https://astronomy.stackexchange.com/a/23106/16685) mentions a [paper by Cuzzi, Hogan, and Bottke](https://arxiv.org/abs/1004.0270) on asteroid formation. It uses numerical methods to investigate models of asteroid formation in order to account for the size distribution in the main asteroid belt and also the Kuiper Belt, and it also gives estimates of the time scales required.
PM 2Ring
<solar-system><orbital-migration>
How young could the asteroid belt be?
Lorry Laurence mcLarry
# How young could the asteroid belt be?

(Asked by: username_0 on 2019-07-20)

I heard a theory (possibly from a crackpot) that there was an event in our solar system where two objects collided and created the asteroid belt, the orbits of some of the planets were altered, and that this event took place late enough for homo sapiens to have referenced observations made during the previous orbit in their oral traditions. (Mars parsing close enough to Earth for people to observe its moons)

Is any of this possible given readily observable evidence?
Are asteroid belts ever created in this way?

**Tags:** solar-system, orbital-migration

> **Comments:**
> **username_1**: I'm too tired right now, to write you an answer, but what you are asking for are the [Grand Tack](https://en.wikipedia.org/wiki/Grand_tack_hypothesis) and the [Nice model](https://en.wikipedia.org/wiki/Nice_model). The asteroid belt being created by a single collision, and Mars being close to earth are both bullshit.  
> **username_2**: There's info online on the youngest earthly meteor shower. It's origin is millions of years ago IIRC, and it surely post-dates the asteroid belt. It is too hot to actually find anything on internet right now, sorry.  
> **username_3**: [This answer by zephyr](https://astronomy.stackexchange.com/a/23106/16685) mentions a [paper by Cuzzi, Hogan, and Bottke](https://arxiv.org/abs/1004.0270) on asteroid formation. It uses numerical methods to investigate models of asteroid formation in order to account for the size distribution in the main asteroid belt and also the Kuiper Belt, and it also gives estimates of the time scales required.  

---

## 2 answers

### Answer by username_4 on 2019-07-21. Score: 3

Dating the age of the asteroid belt is a problem that has to date no general solution.

Rocks are usually dated in the laboratory via [isotopical analysis](https://en.wikipedia.org/wiki/Mass_spectrometry). This is possible for meteorites, but what to do about those rocks that remain in space?

Several methods to date the asteroid belt are known to me, apart from ad-hoc assumptions that it has the same age as the planets:

1. Creating links between dated meteorites and asteroid families: The meteorite family of [L chondrites](https://en.wikipedia.org/wiki/L_chondrite) have possible origin families in the asteroid belt. Those 'families' are small [blobs in the eccentricity-inclination](https://en.wikipedia.org/wiki/Asteroid_family) diagrams, that probably originated in one common parent-body breakup event. Dating meteorites originating from those families, gives minimum ages for the parent bodies of i.e. 500 Myrs for the [Ordovician meteor event.](https://en.wikipedia.org/wiki/Ordovician_meteor_event)
2. Dynamical age modeling: After a breakup of a parent body, the cloud of fragments experience different strengths of [YORP](https://en.wikipedia.org/wiki/Yarkovsky%E2%80%93O%27Keefe%E2%80%93Radzievskii%E2%80%93Paddack_effect) and tidal forces, which causes their semimajor axis distribution to spread. Taking a given distribution, one can [calculate back](https://www.sciencedirect.com/science/article/abs/pii/S0019103502968302) to an age of when the cloud was one particle, i.e. the moment of breakup. This again is a minimum age and found for the Flora family to be more than $10^8$, but less than $10^9$ years. This does exclude a very young belt, but does not say much about the upper age limit.
3. Crater ages: For the largest bodies, i.e. Ceres, Vesta, etc. we can assign [relative ages](https://en.wikipedia.org/wiki/Crater_counting) to the lunar cataclysm. Those usually give ages in excess than 3-4 Gyrs. For bodies like Vesta, where the surface is saturated with craters, this age is a lower limit.
4. Dating of crustal ejecta: There is another family of meteorites that can be linked specifically to Vesta via spectroscopy, called the [HED meteorites](https://en.wikipedia.org/wiki/HED_meteorite). Those meteorites look like they're coming from a differentiated parent body (melted, low siderophile element content), and they containt [CAIs](https://en.wikipedia.org/wiki/Calcium%E2%80%93aluminium-rich_inclusion). Thus, we can date Vesta at least back to the origin of the solar system, as CAIs give us the effective $t0$ for the formation of the solar system.


---

### Answer by username_5 on 2019-07-20. Score: -1

Some of this, as you say, is crackpot stuff, but there have, long ago, been some major collisions in the asteroid belt. The asteroid belt was formed about the same time as the Earth, and these collisions took place quite early on, billions of years before there were any humans. Mars never passed close enough for humans to observe its moons until telescopes were invented, but it does come within 35 million miles on closest approach. Only Venus comes closer at a distance of 26 million miles. The only asteroid belt we can study is our own, but common sense tells us that there must be other solar systems with asteroid belts, created in much the same way as ours. Some of the fragments from these asteroid belt collisions have been propelled Earthwards and left many huge craters, but only the biggest from the last couple of billion years have left identifiable traces. Those from earlier times, especially those that fell in deep ocean, have been eroded and left no visible trace.

> **Comments:**
> **username_2**: Some craters no doubt got subducted.  

---

