Quote Originally Posted by CTPEKO3A
We have an argument with friend of mine. Help, please.
What is a correct way to ask -
Have you been to Mars? or
Have you been on Mars?

Вы бывали на Марсе?
Both are correct. It does not matter in this case.
However, there is a slight difference in meaning.
"to" implies you traveled there
"on" implies that you were standing on the planet. But if you were on Mars, then you travelled there. It does not matter.

Quote Originally Posted by scotcher
It'd be like asking "have you been in Russia?"
It is better to say "Have you been to Russia?"
But you can say "Have you been living in Russia for a long time?"