Why Hart found narrow ecospheres--a minor science mystery solved.
OBJECTIVE
To explain why two NASA computer simulation studies in the 1970s (Hart, 1978 , 1979 ) briefly rocked the subfield of astrobiology and SETI studies by showing very narrow habitable zones (HZs) for solar-type stars. Although other studies later supported wider HZs, it was never clear why the Hart simulations found the narrow limits they did.


RESULTS
Investigation of the state of climate studies and radiative transfer models in the period 1960-1970 provides a likely explanation.


CONCLUSIONS
Hart's findings were in line with earlier results, preventing him from noticing that his radiation model was inadequate.
Unaffiliated, Pittsburgh, Pennsylvania.
Barton Paul
BP
Levenson
D002245:Carbon Dioxide / Q000032:analysis; D017753:Ecosystem; D005118:Extraterrestrial Environment; D008962:Models, Theoretical; D013696:Temperature
D002245:Carbon Dioxide