Identify the fallacy committed in the following argument: There must be intelligent life on other planets. No one has proven that there isn't.

Concluding intelligent life exists merely because its non-existence is unproven is the appeal to ignorance.

The claim rests only on the fact that no one has disproved it.

Absence of a disproof is not positive evidence for the claim.

A gap in knowledge is being treated as if it establishes the conclusion.

Using unproven-false as proof of true is argumentum ad ignorantiam.