Final answer:
A biomarker is a biological marker used to indicate biological processes. In seeking extraterrestrial life, scientists search for molecular signatures and changes on other planets that may indicate the presence of life, such as specific atmospheric gases, or changes in surface composition and light patterns.
Step-by-step explanation:
What is a Biomarker?
A biomarker is a biological marker that is measured and evaluated as an indicator of normal biological processes, pathogenic processes, or responses to an environmental exposure or therapeutic intervention. In the context of searching for life beyond Earth, biomarkers could include molecular signatures like gases in a planet's atmosphere that are associated with life on Earth (e.g., oxygen, methane). Scientists also look for changes in the composition of a planet's surface, as these could indicate the presence of biological activity. Additionally, changes in the light patterns of a planet can suggest the existence of vegetation or other biological material. These are just a few examples of the possible biomarkers that could suggest life exists beyond our solar system.