Buried ice is mapped by how many independent measurements agree with it, not by pumping it. The Subsurface Water Ice Mapping project, SWIM, calls that agreement ice consistency. In those maps, +1 means the data are consistent with ice, 0 means they give no indication either way, and -1 means they are inconsistent with ice. [4] The composite brings those scores onto one map. [1]
The first northern composite used five kinds of evidence: neutrons, thermal behavior, the strength of the SHARAD surface echo, the SHARAD subsurface dielectric, and geomorphology. Later maps split the same idea into depth zones of 0 to 1 m, 1 to 5 m, and deeper than 5 m, because the instruments do not see the same layer. [1] [2]
The classes
A place on this sheet gets one or more of these labels, or none cited. Radar means a SHARAD echo or dielectric that the mappers read as ice-bearing. Geomorphic means a landform such as a debris-covered glacier or scalloped ground. Neutron means the Odyssey spectrometer sees hydrogen in the upper soil. Thermal means the ground warms and cools like icy material. None cited means this sheet is not claiming an ice class there.
SHARAD can see a buried interface. An interface is not a measured tank, and a consistency of +1 is not a purity. Morgan and colleagues found that the broad plains of Arcadia, and the glacial networks of Deuteronilus Mensae, match the greatest number of criteria for accessible ice-rich material equatorward of the present stability zone. [1] Site dossiers records Arcadia in those words. It does not store a cubic meter.
The ice Phoenix touched
Phoenix, in the northern plains, dug to an ice table about 5 cm down. The soil above that table carried the perchlorate range on Perchlorates. [3] Mid-latitude ice and polar ice are different deposits from that shallow table. The polar caps are Polar caps of Mars. Ancient lakes are Water on Mars.
Melting a buried layer is not free water. Sensible heat, latent heat, dirt in the ice, and the salts are all still there. This page does not compute a liter. A screen that ignored Perchlorates would be the wrong screen.
See also
What links here
References
- Morgan et al. Availability of subsurface water-ice resources in the northern mid-latitudes of Mars. Nature Astronomy, 2021. doi 10.1038/s41550-020-01290-z. https://doi.org/10.1038/s41550-020-01290-z
- The Planetary Science Journal. Refined mapping of subsurface water ice on Mars to support future missions. 2025. doi 10.3847/PSJ/ad9b24. Depth zones 0 to 1 m, 1 to 5 m, and deeper than 5 m. https://doi.org/10.3847/PSJ/ad9b24
- Hecht et al. Science 325 (2009). Ice table about 5 cm deep at the Phoenix site. https://doi.org/10.1126/science.1172466
- 51st Lunar and Planetary Science Conference, 2020, abstract 2466. SWIM consistency values of +1, 0, and -1. https://www.hou.usra.edu/meetings/lpsc2020/pdf/2466.pdf