Martian polar ice caps
[7] The total volume of ice in the south polar cap plus the adjacent layered deposits has also been estimated at 1.6 million cubic km.
With the arrival of spring, sunlight warms the subsurface and pressure from subliming CO2 builds up under a slab, elevating and ultimately rupturing it.
This process is rapid, observed happening in the space of a few days, weeks or months, a rate of change rather unusual in geology—especially for Mars.
The gas rushing underneath a slab to the site of a geyser carves a spider-like pattern of radial channels under the ice.
[11][12][13][14] In 2018, Italian scientists reported that measurements of radar reflections may show a subglacial lake on Mars, 1.5 km (0.93 mi) below the surface of the southern polar layered deposits (not under the visible permanent ice cap), and about 20 km (12 mi) across; If confirmed, this would be the first known stable body of water on the planet.
Information about the past climate of Mars may be eventually revealed in these layers, just as tree ring patterns and ice core data do on Earth.
[22]: 155 China's Zhurong rover that has studied the Utopia Planitia region of Mars has found dunes that lie in different directions.
The bright barchans and dark longitudinal dunes is evidence that the predominant wind field underwent a roughly 70° change.
This makes any celestial body's deuterium statistically much less prone to being carried into space by stellar wind compared to its protium.
Evidence that Mars once had enough water to create a global ocean at least 137 m deep has been obtained from measurement of the HDO to H2O ratio over the north polar cap.
In March 2015, a team of scientists published results showing that the polar cap ice is about eight times as enriched with deuterium as water in Earth's oceans.
This means that Mars has lost a volume of water 6.5 times as large as that stored in today's polar caps.
The water for a time may have formed an ocean in the low-lying Vastitas Borealis and adjacent lowlands (Acidalia, Arcadia and Utopia planitiae).
Scientists have even measured tiny changes in the gravity field of Mars due to the movement of carbon dioxide.
High resolution images taken with NASA's Mars Global Surveyor show that the northern polar cap is covered mainly by pits, cracks, small bumps and knobs that give it a cottage cheese look.
Information about the past climate of Mars may be eventually revealed in these layers, just as tree ring patterns and ice core data do on Earth.
Both polar caps also display grooved features, probably caused by wind flow patterns and sun angles, although there are several theories that have been advanced.
NASA's Mars Reconnaissance Orbiter's radar instrument can measure the contrast in electrical properties between layers.
[36][37] In a paper published in Nature in 2023, researches found an abrupt brightness increase in the northern ice cap layers that happened at roughly 0.4 million years ago.
Scientists have even measured tiny changes in the gravity field of Mars due to the movement of carbon dioxide.
On the western hemisphere side of the south pole a low pressure system forms because the winds are changed by the Hellas Basin.
When this occurs, the atmosphere thickens, winds get stronger, and larger areas on the surface can support liquid water.
[43] A large field of eskers exist around the south pole, called the Dorsa Argentea Formation, it is believed to be the remains of a giant ice sheet.
[45][circular reference][46] In July 2018 ESA discovered indications of liquid salt water buried under layers of ice and dust by analyzing the reflection of radar pulses generated by Mars Express.
[47][48][49][50] The upper layer of the Martian south polar residual cap has been eroded into flat-topped mesas with circular depressions.
[51] Observations made by Mars Orbiter Camera in 2001 have shown that the scarps and pit walls of the south polar cap had retreated at an average rate of about 3 meters (9.8 feet) since 1999.
Winds at the surface will blow the escaping gas and dust into dark fans that we observe with orbiting spacecraft.
[31][57] The physics of this model is similar to ideas put forth to explain dark plumes erupting from the surface of Triton.
[58] Research, published in January 2010 using HiRISE images, found that some of the channels in spiders grow larger as they go uphill since gas is doing the erosion.
As soon as the sun rises above the horizon, gas from the spiders blows out dust which is blown by wind to form a dark fan shape.
