Giant Mars mountain Olympus Mons may once have been a volcanic island
Mars' mighty Olympus Mons may have once been a volcanic island surrounded by an ocean nearly 4 miles deep, according to geological evidence found in towering cliffs that ring the extinct volcano.
TroibNews 
Mars' mighty Olympus Mons may have once been a volcanic island surrounded by an ocean nearly 4 miles deep, according to geological evidence found in towering cliffs that ring the extinct volcano.
