alert
alien
attention
ban
believe
black
caution
character
circle
danger
design
draw
drawing
extraterrestrial
fiction
flying
forbidden
graphic
icon
illustration
information
invasion
isolated
martian
monochromatic
monster
mystery
no
no entry
object
prohibited
prohibition
red
safety
science
ship
sign
silhouette
space
spaceship
stop
symbol
tattoo
transport
ufo
unidentified
warning
white
zone