where xi is a planetary property (e.g. surface temperature), xio is the corresponding terrestrial reference value (e.g. 255 K), wi is a weight exponent, n is the number of planetary properties, and ESI is the similarity measure. The weighting exponents are used to adjust the sensitivity of the scale and equalize its meaning between different properties. Earth-like planets can be defined as any planetary body with a similar terrestrial composition and a temperate atmosphere. As a general rule, any planetary body with an ESI value over 0.8 can be considered an Earth-like planet. This means that the planet is rocky in composition (silicates) and could have an atmosphere suitable for most terrestrial vegetation including complex life. Planetary Property Reference Value Weight Exponent. Mean Radius 1.0 Eu Bulk Density 1.0 Eu Escape velocity 1.0 Eu Surface Temperature 288 K 5.58.
