Rampart crater

Usually, rampart craters show a lobate outer margin, as if material moved along the surface, rather than flying up and down in a ballistic trajectory.

[2] Based on images from the Viking program in the 1970s, it is generally accepted that rampart craters are evidence of ice or liquid water beneath the surface of Mars.

The impact melts or boils the water in the subsurface producing a distinctive pattern of material surrounding the crater.

Furthermore, DLEs on sedimentary ground seem to display higher ejecta mobility than those on volcanic surfaces.

They are larger than single layered ejecta craters, having an average diameter of 22 km.

Researchers have analyzed the distribution of both of these craters to determine the thickness of an icy layer that may surround the total surface of Mars.

Remember the single-layered ejecta crater does not penetrate the icy layer, but the multiple-layered does.

It would be equal to 200 meters of water spread over the entire planet, if one assumes 20% pore space.

[6] The Phoenix lander confirmed the existence of large amounts of water ice in the northern regions of Mars.

This finding was predicted by theory and was measured from orbit by the Mars Odyssey instruments, so the idea that rampart crater size shows the depth to ice was confirmed by other space probes.

The image below from the Phoenix lander shows ice that was exposed by the descent engines.

The rampart crater Yuty and its ejecta. This is classified as a multiple-layer ejecta crater.
Rampart crater of the single-layered ejecta type. Arrows indicate the outer edge, called the rampart.
Punsk crater, as seen by CTX camera (on MRO ).
Single-layer ejecta craters only penetrate into the icy upper layer, as shown on the left. Multiple-layer ejecta craters go all the way through the icy layer and somewhat into the lower, ice-free layer (right).
Steinheim crater which shows more than one layer of ejecta. These are called double-layered ejecta craters.
Elath is an example of a double-layered ejecta crater. Viking image.
View underneath Phoenix lander towards south foot pad, showing patchy exposures of a bright surface that was later confirmed to be water ice, as predicted by theory and detected by Mars Odyssey .
A pancake crater. Note the flat top and lack of a visible rampart.