Subjovians And Superterrestrials

Copied from Poul Anderson Appreciation, 22 Nov 2013.

The subjovian planets, Uranus and Neptune, are intermediate in mass between jovians and hypothetical superterrestrials. Not large enough to retain jovian quantities of hydrogen or helium, they instead have stone and metal cores, atmospheric methane and probably also solid ammonia. If such a planet received more solar heat, either in a closer orbit or from a hotter sun, then it would lose even more hydrogen and helium, retaining an atmosphere of hydrogen, methane, ammonia and inert gasses.

Poul Anderson argues in Is there Life On Other Worlds? (New York, 1963) that on such a planet, i.e., a hot subjovian, organic compounds should form and become more complex although the remaining excess of hydrogen would prevent the formation of any cellular chlorophyll plus which, if any oxygen were released, then it would combine with the hydrogen to form water, thus circumventing an Earth-like plant-animal system - although not necessarily preventing the evolution of other kinds of complex organisms. In fact, Anderson argues later in the book that hydrogen-breathers are possible and even probable.

It is important to read this passage carefully because its conclusion:

"...subjovians at reasonably high temperatures seem very likely to be inhabited..." (p. 87)

- refers not, as I initially thought, to Uranus or Neptune, but instead to hypothetical hotter subjovians in other planetary systems.

A superterrestrial:

would have higher gravity, therefore a thicker atmosphere with a stronger greenhouse effect;
thus, would be like Venus if near its sun but cooler further out;
should in the latter case have photosynthesis and an oxygen-nitrogen atmosphere but with more concentrated pre-biological matter leading to faster evolution, also air that would both burn and poison human beings;
but, if smaller, might have habitable mountaintops, like Anderson's Rustum or Niven's Plateau.

(A week away with only one Anderson book means not less blogging but more blogging about a single text. However, this one nonfiction work contains a lot of concentrated information.)

With my granddaughter, who is of Jewish descent through her father, I have just watched Fiddler On The Roof which ends with Russian Jews about to embark for New York where Anderson's works were published...