[1] The Margaritifer Sinus quadrangle covers the area from 0° to 45° west longitude and 0° to 30° south latitude on Mars.

[3] Margaritifer Sinus contains some of the longest lake-chain systems on Mars, perhaps because of a wetter climate, more groundwater, or some of each factor.

[4] A low area between Parana Valles and Loire Vallis is believed to have once held a lake.

[7] Near Holden Crater is a graben, called Erythraea Fossa, that once held a chain of three lakes.

It was decided that the spectra signal spotted from orbit by Mars Odyssey was produced by these spherules.

The concentration of spherules in bedrock could have produced the observed blueberry covering from the weathering of as little as one meter of rock.

The results suggested that the magnetic component of the dust was titanomagnetite, rather than just plain magnetite, as was once thought.

A small amount of olivine was also detected which was interpreted as indicating a long arid period on the planet.

On the other hand, a small amount of hematite that was present meant that there may have been liquid water for a short time in the early history of the planet.

Few rocks were visible on the surface where Opportunity landed, but bedrock that was exposed in craters was examined by the suit of instruments on the Rover.

[20] The Alpha Particle X-ray Spectrometer (APXS) found rather high levels of phosphorus in the rocks.

Similar high levels were found by other rovers at Ares Vallis and Gusev Crater, so it has been hypothesized that the mantle of Mars may be phosphorus-rich.

[22] When Opportunity Rover traveled to the rim of Endeavour crater, it soon found a white vein that was later identified as being pure gypsum.

Observations at the site have led scientists to believe that the area was flooded with water a number of times and was subjected to evaporation and desiccation.

The Viking Orbiters caused a revolution in our ideas about water on Mars; huge river valleys were found in many areas.

Space craft cameras showed that floods of water broke through dams, carved deep valleys, eroded grooves into bedrock, and traveled thousands of kilometers.

Branched streams, studied by the orbiters in the southern hemisphere, suggested that rain once fell.

Large outflow channels on Mars are believed to be caused by catastrophic discharges of ground water.

The OMEGA experiment on Mars Express discovered clay minerals (phyllosilicates) in a variety of places in Aureum Chaos.

[37] Scientists are interested in determining what parts of Mars contained water because evidence of past or present life may be found there.

On April 1, 2010, NASA released the first images under the HiWish program, with the public suggesting places for HiRISE to photograph.

[39] A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.

A detailed discussion of layering with many Martian examples can be found in Sedimentary Geology of Mars.

Martian ground water probably moved hundreds of kilometers, and in the process it dissolved many minerals from the rock it passed through.

The last lake began when water dammed up in Uzboi Vallis broke through a divide, then rapidly drained into Holden crater.

It is hoped that a later mission could then return samples from sites that the Mars Science Laboratory identified as probably containing remains of life.

In the end, it was decided to send the Mars science Laboratory, called "Curiosity", to Gale crater in the Aeolis quadrangle.

The inverted former stream channels may be caused by the deposition of large rocks or due to cementation.

In December 2011, Opportunity Rover discovered a vein of gypsum sticking out of the soil along the rim of Endeavour crater.

[57][58][59][60] Indeed, a study published in June 2017, calculated that the volume of water needed to carve all the channels on Mars was even larger than the proposed ocean that the planet may have had.