Science Olympiad Solar System Practice Test 2026 – Complete Study Resource

Io, one of Jupiter's moons, is known for its striking yellowish-orange coloration, which is primarily due to sulfur compounds that are emitted from its numerous active volcanoes. The surface of Io is covered with a variety of sulfur forms, including yellow and red sulfur, which result from the intense volcanic activity characteristic of this moon.

The extreme geothermal conditions on Io create a dynamic environment where sulfur and other compounds are erupted in large quantities, leading to the formation of colorful volcanic plains and features. The interplay of temperature and pressure allows these sulfur compounds to exist in different forms, contributing to the vivid coloration observed on the surface.

This phenomenon is distinct from the other options, which do not explain Io's coloration as effectively. Iron oxide deposits do not dominate the surface composition; volcanic activity is much more pronounced. Additionally, while meteor impacts may influence the surface, they do not contribute significantly to the characteristic yellowish-orange hues of Io. Organic materials are not a primary feature of Io's surface composition and would not explain the observed coloration. Therefore, the presence of sulfur compounds from volcanic activity is the main reason for Io's distinctive appearance.