The basic requirements for the development of life on Earth:
- a long-lived star (at least 4 billion years old)
- liquid water (exists as a liquid over a wide temperature range and
ice floats adding climatic stability)
- source of energy (sunlight, lightning, chemical, geothermal, tidal)
- supply of biogenic elements (C H O N S P + Na K Mg Ca Cl):
these are abundant in the present day universe
- atmosphere (ozone for protection from ultraviolet light)
- stable environment (extinctions; distant Jovian planets)
The example of Earth suggests that there are 3 parameters for life
to succeed on a planet:
- the right distance from the central star
- the right total mass
- (possibly) a large, orbiting satellite
