We've long known (since Mariner 9 spectroscopy in 1972) that Mars' polar ice caps consist of a combination of water and dry ices and grow & shrink each season t

We've long known (since Mariner 9 spectroscopy in 1972) that Mars' polar ice caps consist of a combination of water and dry ices and grow & shrink each season through direct deposition of water vapor from the atmosphere (sublimating back into water vapor in the spring, with no liquid phase). Mars Phoenix (which landed in the upper northern hemisphere and dug for soil samples) was intended to figure out whether the ground environment near the ice cap was conducive to life. It found that the soil does contain water ice distributed throughout it, but also contains hostile perchlorates. More recently, satellite imagery has found evidence of liquid water, both in seasonal flows on mid-latitude slopes (as a briny mixture with low freezing temp), and in underground lakes beneath the south polar ice cap. tl;dr: This Korolev crater pic is a fun pretty-picture post offering an opportunity to educate readers with a seasonal twist. No new science here.