Measurement of the spectrum of light reflected from a planet gives us information on its

• A. Distance
• B. Temperature
• C. Chemical composition
• D. Mass

Answer: (C)

A planet’s reflected spectrum acts like a fingerprint for its chemical makeup, because different molecules absorb and reflect light at specific wavelengths. When light from a star bounces off a planet, certain wavelengths are absorbed by the planet’s atmospheric gases or surface materials, leaving characteristic dark lines or bands in the spectrum. By identifying these features and their strengths, we can infer which chemicals or minerals are present on or above the planet, such as water vapor, methane, oxygen, or various minerals.

Distance and mass aren’t directly read from a reflected spectrum. The spectrum tells you what’s there, not how far away the planet is or how much it weighs. Temperature can influence the overall color or intensity of the spectrum in some cases, but the most direct and informative reading from a reflected spectrum is the planet’s chemical composition.