Assertion: soil's mineral | /r/HasProperty | exposed to ultraviolet rays
Facets:
value: in sunlight
type: LOCATION
Source sentences:
text: The reddish hue is due to rusting iron minerals presumably formed a few billion years ago when Mars was warm and wet, but now that Mars is cold and dry, modern rusting may be due to a superoxide that forms on minerals exposed to ultraviolet rays in sunlight.