We're all familiar with the Mars fantasies of 1908-1909, but knowledge of Huxley and Wallace's amazingly correct conjectures about Mars during this period is little known. For that matter it is extremely difficult to find even very limited report of it, but from what I've read in limited secondary materials, the following seems to sum it up.

Working from an incredible small set of facts, at least these two managed to make some very accurate conjectures as to the true state of Mars.

First, the two knew Mars' mass. They correctly inferred a low atmospheric density on Mars from this.

Second, the two knew Mars' distance from the sun. They correctly inferred cold temperatures from this.

Third, the two knew that Mars showed seasonal polar activity. Given 1 and 2, they infered that CO2 was the only viable working fluid for this phenomeneon.

(This last point I'm not too certain of, but then see the intro to this note.)

ep