Researchers, writing in Icarus, have described layered units in the Aeolis quadrangle at Aeolis Dorsa.
 A deposit that contains yardang was formed after several other deposits.
 The yardangs contain a layered deposit called "rhythmite" which was thought to be formed with regular changes in the climate.
 Because the layers appear harden, a damp or wet environment probably existed at the time.
The authors correlate these layered deposits to the upper layers of Gale crater’s mound (Mt. Sharp).

Many places on Mars show rocks arranged in layers.
 Sometimes the layers are of different colors.
 Light-toned rocks on Mars have been associated with hydrated minerals like sulfates.
 The Mars Rover Opportunity examined such layers close-up with several instruments.
 Some layers are probably made up of fine particles because they seem to break up into find dust.
 Other layers break up into large boulders so they are probably much harder.
Basalt, a volcanic rock, is thought to in the layers that form boulders.
 Basalt has been identified on Mars in many places.
 Instruments on orbiting spacecraft have detected clay (also called phyllosilicate) in some layers.
 Recent research with an orbiting near-infrared spectrometer, which reveals the types of minerals present based on the wavelengths of light they absorb, found evidence of layers of both clay and sulfates in Columbus crater.
 This is exactly what would appear if a large lake had slowly evaporated.
 Moreover, because some layers contained gypsum, a sulfate which forms in relatively fresh water, life could have formed in the crater.

Scientists were excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water.
 Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life.

Rock can form layers in a variety of ways.
 Volcanoes, wind, or water can produce layers.
 Layers can be hardened by the action of groundwater.
 Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through.
 When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents.
Consequently, layers of dust could not later easily erode away since they were cemented together.
On Earth, mineral-rich waters often evaporate forming large deposits of various types of salts and other minerals.
Sometimes water flows through Earth's aquifers, and then evaporates at the surface just as is hypothesized for Mars.
 One location this occurs on Earth is the Great Artesian Basin of Australia.
 On Earth the hardness of many sedimentary rocks, like sandstone, is largely due to the cement that was put in place as water passed through.
Researchers, writing in Icarus, have described layered units in the Aeolis quadrangle at Aeolis Dorsa.  A deposit that contains yardang was formed after several other deposits.  The yardangs contain a layered deposit called "rhythmite" which was thought to be formed with regular changes in the climate.  Because the layers appear harden, a damp or wet environment probably existed at the time. The authors correlate these layered deposits to the upper layers of Gale crater’s mound (Mt. Sharp).
Many places on Mars show rocks arranged in layers.  Sometimes the layers are of different colors.  Light-toned rocks on Mars have been associated with hydrated minerals like sulfates.  The Mars Rover Opportunity examined such layers close-up with several instruments.  Some layers are probably made up of fine particles because they seem to break up into find dust.  Other layers break up into large boulders so they are probably much harder. Basalt, a volcanic rock, is thought to in the layers that form boulders.  Basalt has been identified on Mars in many places.  Instruments on orbiting spacecraft have detected clay (also called phyllosilicate) in some layers.  Recent research with an orbiting near-infrared spectrometer, which reveals the types of minerals present based on the wavelengths of light they absorb, found evidence of layers of both clay and sulfates in Columbus crater.  This is exactly what would appear if a large lake had slowly evaporated.  Moreover, because some layers contained gypsum, a sulfate which forms in relatively fresh water, life could have formed in the crater.
Scientists were excited about finding hydrated minerals such as sulfates and clays on Mars because they are usually formed in the presence of water.  Places that contain clays and/or other hydrated minerals would be good places to look for evidence of life.
Rock can form layers in a variety of ways.  Volcanoes, wind, or water can produce layers.  Layers can be hardened by the action of groundwater.  Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through.  When ground water surfaces in low areas containing sediments, water evaporates in the thin atmosphere and leaves behind minerals as deposits and/or cementing agents. Consequently, layers of dust could not later easily erode away since they were cemented together. On Earth, mineral-rich waters often evaporate forming large deposits of various types of salts and other minerals. Sometimes water flows through Earth's aquifers, and then evaporates at the surface just as is hypothesized for Mars.  One location this occurs on Earth is the Great Artesian Basin of Australia.  On Earth the hardness of many sedimentary rocks, like sandstone, is largely due to the cement that was put in place as water passed through.
Aeolis quadrangle