As Free As Air

From the Cut n Paste

当一个人没有约束，没有责任时，他可真像空气般自由了！我们便形容他“ As Free As Air ”。

Example

Last year Manfred retired. " My time is my own now," he smiled. " I'm as free as air". To be as free as air is to be unrestrained and to have no obligations. Imagine we have this expression because, as no one owns the air, it costs us nothing to use it.

For me

I think i cannot use " as free as air" in the Mars.

Thanks God, i am on the earth =.=''