Ancient Mars once had surprisingly frigid primeval oceans complete with their own icebergs, new evidence suggests. Now researchers have found evidence of icebergs on Mars, supporting a third idea of the Red Planet's ancient climate — that of a cold and wet Mars, governed by oceans or seas covered partly in ice, as well as glaciers and massive polar caps. [Photo evidence of past Mars icebergs.] Images captured by the HiRISE camera aboard NASA's Mars Reconnaissance Orbiter revealed the presence of boulders about 1.5-6.5 feet (0.5-2 meters) across, as well as chains of roughly one or two dozen craters measuring 330-1,300 feet (100-400 meters) wide scattered throughout the northern plains. Both these details are hard to reconcile with the notion of fine-grained sediments deposited on a deep ocean basin, and had been used to cast doubts on the concept of an ocean on Mars.
They suggest glaciers in the highlands could have eroded the terrain, transporting rock within them and on their surfaces. Armadas of icebergs would have formed at the edges of glaciers as they melted and broke apart, which could then float thousands of miles on the ocean before they disappeared, depositing rock downward.
Also, on Earth, when icebergs scrape against the ocean floor, they can rain boulders down in clumps, which could explain boulder clusters up to about a mile (1.6 km) wide that scientists have seen on Mars. In addition, when icebergs roll along the sea floor on Earth, they can generate strings of dents, perhaps explaining the chains of craters seen on the Martian lowlands.
If there were icebergs, then there were open and sizable bodies of stable liquid water on the surface of Mars. Space.com
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