Columbia subject headings:
Exobiology.
Mars (Planet)--Geology.
Mars (Planet)--Water.
Harvard subject headings:
Astrophysics
Exobiology.
Life sciences.
Mars (Planet)--Geology.
Mars (Planet)--Water.
Physical geography.
Physics.
Princeton subject headings:
Exobiology.
Mars (Planet)--Geology.
Mars (Planet)--Water.