What is the dark romanticism?
What are some famous authors and pieces?

martians or other types of aliens represent a unique fear as opposed to zombies. vampires and other types of monsters.   in most sci-fi stories, aliens come from other worlds and have different or more advanced technology.   abductions and experimentation on human bodies that involve these technologies, or the use of these technologies against human beings and the use of unknown "powers", are a type of fear that's different from that of other types of monsters.  

the symbol of the grandfather's heritage in this excerpt from "the medicine bag,” is the beaded bolo tie.

a bolo tie is a cord fastened around the neck with an ornamental clasp which is worn as a necktie. they have been used by native american tribes such as hopi, navajo, zuni, and puebloans since the mid-20th century.

therefore, the fact that the grandfather is wearing a bolo tie refers to his heritage as native american.