For me, they are anotherdifferent things in Chinese and English.

- I believe her when she says she uses lotion, in ice rink environment, the because/; (her) skin dries very quickly.

An independent sentence (a sentence that makes sense on its own), followed by another independent sentence needs a semi colon. Or else, you have to have a conjunction like "because" or "as."

why there isn't any conjecture behind the comma?

Conjecture doesn't make sense here because it means an opinion/conclusion. I think you mean conjunction?

Anyways like I said, that sentence is wrong. It needs a conjunction OR needs a semi-colon (;) instead of a comma.
This is because a comma is not strong enough to link two independent sentences.

Alternatively, you can replace the comma with a full stop.

It is sometimes argued that people should dedicate to the colonization of Mars.

dedicate what? dedicate is a transitive verb and needs an object afterwards
- dedicate themselves/resources/their time

Admittedly, thea Mars colony could prevent humanity from the risk of planetary extinction.

there is no specific Mars colony so you have to use "a"

Firstly, colonizing Mars does not help in solvinge any of our existing problems.

That is to say, issues like overpopulation, environmental protection, and starving need to be urgently addressed, but there is nothing with which a Mars colony can help within a short time.

Or "there is nothing a Mars colony can help with" (technically not grammatically correct but far more common, especially in spoken English)

Secondly, there is not any economic reason for us to do so.

there is not any --> there is no (noun)

I believe that humans already have a sufficient level of technology for this plan, but the limiting factors always lie in costendeavor, but cost is always a part of the limiting factors.

There is not really a specific plan to colonise Mars right now and it's more of a goal. So I would not use "plan"

The way you phrased it before was a bit ambigious as in whether the cost was a part of limiting factors, or if limiting factors was a part of the cost

Most of the colonization that happened on eEarth had economic incentives, such as spices or gold, which can reap peopleenabled people to reap rewards in a short period of time.

You are talking about the past so I changed it to past tense
Earth is proper noun
reap + (two nouns) sounds weird, so I changed it so people is the subject

In conclusion, I believe that many factors need to be considered, and there are more issues call for urgenturgent issues to be solvinged on Earth.

- I believe her when she says she uses lotion, in ice rink environments, the skin dries very quickly.

why there isn't any conjecture behind the comma?

When you're giving a reason for something in English, it's usually ok to omit "because" so long as it doesn't start the sentence.

"This is disgraceful, (because) look at the mess!"
"I'm going home, (because) it's getting late"
"Your son has been performing poorly, (because) he needs to study more"
"I believe her when she says she uses lotion, (because) in ice rinks, the skin dries very quickly."

It is sometimes argued that people should dedicate themselves to the colonization of Mars.

Admittedly, thea Mars colony could prevenotect humanity from the risk of planetary extinction.

You could say:
"Admittedly, a Mars colony could prevent the risk of planetary extinction."

That is to say, issues like overpopulation, environmental protection, and starvingglobal climate change, and world hunger need to be urgently addressed, but there is nothing a Mars colony canould help with in athe short timeerm.

Secondly, there is not any economic reason for us to do so.

I believe that humans already have a sufficient level of technology for this plan, but the limiting factors always lie in cost.

"humanity" may be a more appropriate word to use when talking about human society in general.
"
I believe that humanity already has a sufficient level of technology...
"

Most of the colonization that happened on eEarth had economic incentives, such as spices or gold, which can reap people rewards in a short period of time.

To be more specific, it does not make sense to invest a bunch of costsso much in order to colonize Mars without any short-term benefit.

As an aside, "a bunch" is quite casual language. It may not be very appropriate for this style of writing.

In conclusion, I believe that many factors need to be considered, and that there are more pressing issues that call for urgent resolvingutions on Earth.

- I believe her when she says she uses lotion, in an ice rink environment, the skin dries very quickly.

It is sometimes argued that people should dedicate their lives to the colonization of Mars.

That is to say, issues like overpopulation, environmental protection, and starvfaminge need to be urgently addressed, butand there is nothing any Mars colony canould help with, within a short time.

I believe that humans already have a sufficient level of technology for this plan, but the limiting factors always lie in the cost.

In conclusion, I believe that many factors need to be considered, and there are more issues that call for urgent solving on Earth.