"Summer in the southern hemisphere occurs when Mars is at the closest to the sun in its orbit."
(Source)

"Although Mars does have seasons, the temperature only varies from cold to
extremely cold."
(Source)

You can set the Solar System Live page to show Mars' position on Tuesday, June 19, 2001. The green/blue color changes show the planet above and below the ecliptic, but can also be used to approximately determine the planet’s vernal and autumnal equinox. The picture was apparently taken as Mars was just entering a southern hemisphere summer. The current season, btw (Saturday, July 27, 2002), looks like about mid summer for the northern hemisphere.

With only subzero temp changes to work with, however, it might be considered more logical that what your seeing is the dust from a “very” recent collapse.

Or not. A high albedo mineral deposit remains very possible -- and seasonal sublimation of a large quantity of enclosed water might be visible against the background of Mars. I don’t have the formulae to make any decision on this, nor would I expect that a physical experiment of the scope shown in the pic was ever conducted here on Earth, so this is merely conjecture.

Dan