A Martian Odyssey (novella) by Stanley G. Weinbaum
Dick Jarvis crash-lands into one of the Thyle regions of Mars. Rather than sit and wait for rescue, Jarvis decides to walk back north to the Ares, but he could never have foreseen the wonders and dangers that lay ahead.
"A Martian Odyssey" immediately established Weinbaum as a leading figure in science fiction. Isaac Asimov states that Weinbaum's "easy style and realistic description of extraterrestrial scenes and life-forms were better than anything yet seen, and the science fiction reading public went mad over him." The story "had the effect on the field of an exploding grenade. With this single story, Weinbaum was instantly recognised as the world's best living science fiction writer, and at once almost every writer in the field tried to imitate him."
Tweel itself was one of the first characters (arguably the first) who satisfied John W. Campbell's famous challenge: "Write me a creature who thinks as well as a man, or better than a man, but not like a man."