Earth Similarity Index

The Earth Similarity Index (English for Erdähnlichkeits index), short ESI, is a scale for assessing the similarity of a celestial body with the earth. The value is between 0 and 1, wherein the ground has a value of 1. It was developed for planets and exoplanets, but can also be applied to other objects. ESI is calculated from the radius, the density, the velocity and the cosmic temperature at the surface. Within our solar system, Mars is equal to 0.697 for Earth the object with the second largest ESI. Gliese 581 g is among the exoplanets with 0,889 currently the one with the highest ESI, but this still is one of the previously confirmed (end of 2013).

The ESI 2011 was proposed by members of the Planetary Habitability Laboratory ( PHL ) of the University of Puerto Rico. It has the surface temperature as a key parameter and the earth together with the concept of the habitable area as a reference. He does not serve as a measure of habitability. In addition to the ESI (English for planetary habitability index), short PHI, suggested by the authors nor the Planetary Habitability Index.

Calculation

Parameter is considered in each case, and compares the value of the earth with the corresponding value of the observed object. For this purpose, a kind of symmetrical relative deviation is inverted so that identical values ​​1 and 0 on the greatest possible deviation:

The ESI is determined as a weighted geometric mean of these deviations:

The ESI is also used in two particular aspects: the interior ESI (English for internal ESI ) is calculated only using the two parameters radius and density; the surface ESI (English for surface ESI ) in accordance of the two other parameters. The following table lists the set for the ESI weightings and an example of the values ​​for the planet Venus are listed below:

The ESI for the planet Venus results are thus: