Planet Formation and Habitable Zones
This page delves into the process of planet formation and the concept of habitable zones within solar systems.
Planet formation begins with gravity condensing supernova dust. The inner mass heats up and initiates nuclear reactions, forming a star. Inner planets are stripped of lighter elements, while outer planets retain them.
Definition: Rocky planets consist of metallic cores and silicate crust/mantle with thin or no atmospheres. Gas giants have dense atmospheres of hydrogen and helium with no solid surface.
The habitable zone (HZ) is introduced as the region around a star where liquid water can exist on a planet's surface. However, the page emphasizes that being in the HZ doesn't guarantee a planet can support life.
Highlight: The habitable zone in a solar system moves outward over time as the star's energy output increases.
The page then provides detailed information about Venus and Mars, comparing them to Earth:
Example: Venus, despite being similar in size to Earth, has temperatures exceeding 800°F and a dense CO2 atmosphere with sulfuric acid rain.
Example: Mars, with about 1/10 of Earth's mass, has a thin CO2 atmosphere and evidence of past liquid water on its surface.
These examples illustrate the diversity of planetary conditions even within our own solar system's habitable zone.