In 1940, science-fiction art pionneer Frank R. Paul did pieces showing what life could be on other planets. In his own words:
"Science tells us that is is logical to believe that other planets are inhabited by some form of life. Just what type isn't exactly certain, but astronomy points toward definite planetary conditions which can be taken into consideration in imagining what type of "man" that planet would be most likely to develop. On our [front] cover we have conceived of the Man from Mars, as he most logically might exist.
Mars, the oldest of planets, cooled faster than its larger brothers. Its location also aided in its rapid advance, and life must have appeared there long before on earth. Therefore, our Martian must be more advanced, more evolved than we. Considering his planetary environment he would most likely possess the following features...The Man from Mars... is a strange looking individual. He has been evolved much differently than we because mars is a smaller planet, has less gravity, a thin atmosphere and extreme heat and cold. He has large ears to catch sound weakened by rarefied air. He communicates with his fellows by telepathy, using natural antenna. He is tall, walking with the aid of natural suction-type feet. he has magnificent lung development, and narrow, light body. he has retractable eyes and nose, to protect against freezing. his body, besides being protected by scientific garments, is covered with warm fur. Geing the most advanced creature in the solar system, he carries an atomic riffle, the result of greater science knowledge.
How Martians see us.
A Martian reconstruction of the Earthman, deduced from what he can discover of our world by observation and analysis, might very logically be such a creature as is shown here.The Martians had deduced that, since Earth is three-quarters water, then humans would probably be quasi-amphibian. Due to the abundance of food, he would be a "fat, contented creature, with a large body, bullet-head, short legs, and webbed hands and feet... [W]e of Mars can well be jealous of Earth and its inhabitants. (Thanks to Frank Wu for this bit of text. Please visit his fantastic site - the most complete on Frank R. Paul, at: http://www.frankwu.com/Paul-listing.html)