<P> Scientific findings since the 1990s have greatly influenced the scope of the fields of astrobiology , models of planetary habitability and the search for extraterrestrial intelligence ( SETI ) . NASA and the SETI Institute have proposed categorising the increasing number of planets found using a measure called the Earth Similarity Index ( ESI ) based on mass , radius and temperature . According to this measure , as of 23 July 2015 , the confirmed planet currently thought to be most similar to Earth on mass , radius and temperature is Kepler - 438b . Scientists estimate that there may be billions of Earth - size planets within the Milky Way galaxy alone . </P>
<P> Scientific findings since the 1990s have greatly influenced the scope of the fields of astrobiology , models of planetary habitability and the search for extraterrestrial intelligence ( SETI ) . NASA and the SETI Institute have proposed categorising the increasing number of planets found using a measure called the Earth Similarity Index ( ESI ) based on mass , radius and temperature . According to this measure , as of 23 July 2015 , the confirmed planet currently thought to be most similar to Earth on mass , radius and temperature is Kepler - 438b . Scientists estimate that there may be billions of Earth - size planets within the Milky Way galaxy alone . </P>
which planet is most similar in temperature to earth
which planet is most similar in temperature to earth
Kepler - 438b
Kepler - 438b