How do you normally ask about the probability / likelihood of something in English?
Example:
The number of artificial satellites is increasing and the gravitational force is acting up on them. But the question is that:
a. How much is the probability of striking of artificial satellites in space?
b. How much is the likelihood of striking of artificial satellites in space?
Please kindly let me know whether both of these expressions are fixed or there is only one correct expression between them. If so, which one is that? Is there any better expression to ask about it in English?