Re: If a tree was planted on the moon, would it grow a

Paulina,
Technically, yes, you could do what you asked---but there are a lot of reasons why it wouldn't be practical to do so on the moon. It is true that plants "breathe" in carbon dioxide (CO2) and give off oxygen (O2). However, you would have to launch a lot of equipment to the moon in order to get started. You would need soil, materials to build an air shield, CO2, water for the trees, etc. This would be more than the rockets we have today can handle. You can think of this in terms of going on a day hike in the woods: you could bring along a stove, pots and pans, spices, meat, vegetables, etc., and cook your lunch wherever you want to eat it, but it's a lot easier to bring along an already prepared lunch.

However, your idea is very applicable to another place in our solar system: Mars. The atmosphere on Mars is almost all carbon dioxide, so you would not need to bring it with you. Also, near the polar regions there is frozen water which could be used for the plants.

This process you thought of about modifying another planet (or moon) to be habitable by humans is called "Terraforming" and How Stuff Works explains how this might work on Mars.

So, you can see that you are not alone in wanting to make other places in the solar system livable! It certainly would be nice to go to these places without needing a spacesuit someday---hopefully you can be one of the people that makes it happen!

-Steve