Final answer:
The observed disk-shaped region of young stars with planets in formation led scientists to confirm the Nebular Hypothesis of how our solar system was formed.
Step-by-step explanation:
The confirmation of the Nebular Hypothesis, which explains the formation of our solar system, was led by the observed disk-shaped region of young stars with planets in formation. This provided evidence that similar processes, such as the coalescence of material into planetesimals, could happen in other planetary systems as well.
Observations of the planet Mars, the discovery of the Moon's origin, and geological evidence from Earth are not directly related to confirming the Nebular Hypothesis.