For decades, astrophysicists have grappled with the "Faint Young Sun Paradox." Standard stellar evolution models indicate that during the Archean eon, approximately three billion years ago, the Sun shone with only 70 to 80 percent of its current intensity. Under such conditions, liquid water should have frozen globally, yet geological evidence—such as water-worn sedimentary rocks and fossilized ripple marks—proves that a liquid ocean existed. Early explanations attributed this anomaly to a massive greenhouse effect caused by extreme levels of carbon dioxide or ammonia. However, geological samples from the period reveal that carbon dioxide levels were insufficient to compensate for the weaker sun, and ammonia is rapidly destroyed by solar ultraviolet radiation. Instead, modern research points toward a dynamic interplay of factors: lower planetary albedo due to smaller continental landmasses, combined with biologically produced methane from early microbes. This delicate balance prevented a runaway glaciation.
Which of the following statements best expresses the main idea of the passage?
- AAstrophysical models of stellar evolution are frequently contradicted by geological findings on Earth.
- BEarly atmospheric carbon dioxide and ammonia were insufficient to explain how liquid water existed during the Archean eon.
- The Earth's early habitability was maintained by a complex, self-regulating synergy of geological and biological processes.Cevap
- DEarly microbes were the sole factor responsible for preventing the Archean Earth from undergoing a global glaciation.