The name 
Martian is given to the hypothetical native inhabitants of the planet 
Mars.
There have been many fictional depictions of Martians in the past, including the famous invaders from H. G. Wells' novel The War of the Worlds, and also many people who have believed in the existence of real Martians.  At this point in time it is generally accepted that Mars has no macroscopic native life, and even the presence of bacteria-scale life is speculative at best. 
If Mars is one day colonized by humans, the generations descended from the settlers will most likely also be called Martians.
See also Mars in fiction, extraterrestrial life.
In a 
computer network, packets with source addresses not routable by some computer on a network segment are referred to as 
martians or "packets from Mars", on the grounds that they are of no evident "terrestrial" (i.e. normal) source. Martian packets can arise from network equipment malfunction, misconfiguration of a host, or simple coexistence of two logical networks on a single physical layer. For instance, if the 
IP networks 192.168.34.0/24 and 10.2.3.0/24 network operate on the same 
Ethernet segment, packets from 10.2.3.4 are Martians to the computer at 192.168.34.9, and vice versa.
The 
Martians were a group of physicists and mathematicians who emigrated from 
Hungary to the 
United States in the early half of the 
20th century.  They included 
Wigner[?] and 
Edward Teller.  They received the name from 
John von Neumann who half-jokingly suggested that Hungary was a front for aliens from Mars.
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