<p>In the accretion phase of a planet, along with the H/He gas, there are dust particles or heavy elements in the gas phase accreted into the outer shell of a planet (or THE planet in the case of gas giants).<br />
Should the fraction of this heavy element X in relation to H/He, i.e. the number <span class="math-container">$\rm [X/H]$</span> increase through this process, we speak of enrichment.  If it decreases, we speak of depletion.</p>
<p>However, and absolute value of <span class="math-container">$\rm [X/H]$</span> might not be indicative of interesting physics. Instead, usually <span class="math-container">$\rm [X/H]$</span> is compared to a standard value, e.g. that of the solar atmosphere <span class="math-container">$\rm [X/H]_{\odot}$</span>. This is because the primordial nebula will have had some base number of heavy elements in it, and only having <em>more</em> heavy elements than that base-line value will count as enriched.<br />
I.e. if your element has abundance X with <span class="math-container">$\rm [X/H]-\rm [X/H]_{\odot}=0$</span>, is has neither enriched nor depleted abundance, but <em>solar</em> abundance. If it has <span class="math-container">$\rm [X/H]-\rm [X/H]_{\odot}&gt;0$</span> it is <em>enriched relative to the solar value</em>.</p>
<p>So those are two slightly different meanings of enrichment, which one is in use depends on the text you are reading.</p>

CC BY-SA 4.0
2021-10-22T16:14:59.610Z
2021-10-22T16:14:59.610Z
AtmosphericPrisonEscape
<p>While I was researching about planet formation, I repeatedly came across the term <em>envelope enrichment</em>. What does this mean?</p>
<p>I searched it up and looked at many websites, but no helpful definitions showed.</p>
<p>Thanks in advance!</p>

CC BY-SA 4.0
2021-10-22T15:21:00.263Z
I'm pretty sure "enrichment" refers to the presence/production of heavy elements (i.e., metals) in the planet's atmosphere
Daddy Kropotkin
CC BY-SA 4.0
2021-10-22T15:37:05.923Z
It's my cynical friday feeling coming through, but it sounds awfully like when politicians get an envelope full of money "anonymously". :-)
StephenG - Help Ukraine
<planetary-formation><terminology>
Envelope Enrichment?
asterism
# Envelope Enrichment?

(Asked by: username_0 on 2021-10-22)

While I was researching about planet formation, I repeatedly came across the term *envelope enrichment*. What does this mean?

I searched it up and looked at many websites, but no helpful definitions showed.

Thanks in advance!

**Tags:** planetary-formation, terminology
> **Comments:**
> **username_1**: I'm pretty sure "enrichment" refers to the presence/production of heavy elements (i.e., metals) in the planet's atmosphere  
> **username_2**: It's my cynical friday feeling coming through, but it sounds awfully like when politicians get an envelope full of money "anonymously". :-)  

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## 1 answers

### Answer by username_3 on 2021-10-22. Score: 2 | Accepted answer

In the accretion phase of a planet, along with the H/He gas, there are dust particles or heavy elements in the gas phase accreted into the outer shell of a planet (or THE planet in the case of gas giants).  
Should the fraction of this heavy element X in relation to H/He, i.e. the number $\rm [X/H]$ increase through this process, we speak of enrichment. If it decreases, we speak of depletion.

However, and absolute value of $\rm [X/H]$ might not be indicative of interesting physics. Instead, usually $\rm [X/H]$ is compared to a standard value, e.g. that of the solar atmosphere $\rm [X/H]\_{\odot}$. This is because the primordial nebula will have had some base number of heavy elements in it, and only having *more* heavy elements than that base-line value will count as enriched.  
I.e. if your element has abundance X with $\rm [X/H]-\rm [X/H]\_{\odot}=0$, is has neither enriched nor depleted abundance, but *solar* abundance. If it has $\rm [X/H]-\rm [X/H]\_{\odot}>0$ it is *enriched relative to the solar value*.

So those are two slightly different meanings of enrichment, which one is in use depends on the text you are reading.


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