Please answer the question below?
6. Scientists consider life to be possible on faraway planets if space exploration shows that water may exist on those planets.
The sentence above contains dependent or independent idea. "Scientists consider life to be possible on faraway planets" is the dependent or independent idea, and "if space exploration shows that water may exist on those planets" is the idea. A comma is not necessary in this sentence because the independent idea comes first, dependent idea comes first or subcoordinating junction is if .