[8] In eastern Ismenius Lacus, lies Mamers Valles, a giant outflow channel.

The giant impact crater, Lyot, is easy to see in the northern part of Ismenius Lacus.

Research, published in June 2010, described evidence for liquid water in Lyot crater in the past.

Research, published in 2017, concluded that the channels were made from water released when the hot ejecta landed on a layer of ice that was 20 to 300 meters thick.

The existence of these channels is unusual because although Mars used to have water in rivers, lakes, and an ocean, these features have been dated to the Noachian and Hesperian periods—4 to 3 billion years ago.

Since the collision that produces a crater is like a powerful explosion, rocks from deep underground are tossed unto the surface.

In fretted terrain the land seems to transition from narrow straight valleys to isolated mesas.

Eventually, proof of their true nature was discovered by radar studies with the Mars Reconnaissance Orbiter showed that they contain pure water ice covered with a thin layer of rocks that insulated the ice.

Much of the area in high latitudes, especially the Ismenius Lacus quadrangle, is believed to still contain enormous amounts of water ice.

[16][19][21] In March 2010, scientists released the results of a radar study of an area called Deuteronilus Mensae that found widespread evidence of ice lying beneath a few meters of rock debris.

[23] It would be difficult to take a hike on the fretted terrain where glaciers are common because the surface is folded, pitted, and often covered with linear striations.

The ice goes directly into a gas (this process is called sublimation) and leaves behind an empty space.

Many features on Mars, especially ones found in the Ismenius Lacus quadrangle, are believed to contain large amounts of ice.

[29] Furthermore, at this high tilt, stores of solid carbon dioxide (dry ice) sublimate, thereby increasing the atmospheric pressure.

[28] When the tilt begins to return to lower values, the ice sublimates (turns directly to a gas) and leaves behind a lag of dust.

[32][33] The lag deposit caps the underlying material so with each cycle of high tilt levels, some ice-rich mantle remains behind.

[34] Note that the smooth surface mantle layer probably represents only relative recent material.

Some places in the Ismenius Lacus quadrangle display large numbers of cracks and pits.

It is widely believed that these are the result of ground ice sublimating (changing directly from a solid to a gas).

A large team of scientists described how some of the surface in Ismenius Lacus quadrangle was altered by two tsunamis.

Calculations show that the average height of the waves would have been 50 m, but the heights would vary from 10 m to 120 m. Numerical simulations show that in this particular part of the ocean two impact craters of the size of 30 km in diameter would form every 30 million years.

The parts of Mars studied in this research are Chryse Planitia and northwestern Arabia Terra.