ON THE ORIGIN OF TITAN’S ARCTIC “COOKIE CUTTER” LAKES

Since first observing surface liquids on Titan, 100s of lake basins have been discovered, some filled with liquids, others apparently empty, mostly in the arctic region. Of these, the “cookie cutter” lakes are particularly enigmatic. These features vary from a few to 10s of km in diameter, contained within steep-rimmed (up to 100s of m) circular or sub-circular and apparently self-contained depressions. Sometimes they are nested or overlapping, and occasionally they appear to be incised into a rampart or “blister”-like mound.

The scale of “cookie cutter” lakes, and their frequent incision onto mounds, led to early interpretation as a cryovolcanic origin. However, the basins seem to be intimately connected with the most active of hydrological environments on Mars, and so a coupled causal relationship is strongly indicated. Karstic or karst-like processes have evolved as the preferred interpretation of the basins, given that many of the photochemically-derived organic solids are soluble in the surface liquid alkanes, methane and ethane, and that alternative widespread periglacial processes do not appear to be viable on Titan.

This interpretation presents some problems: The scale of the basins is greater than equivalent terrains on Earth, the presence of the ramparts associated with some of the basins is hitherto unexplained, and the total volumes of inferred soluble solids implied for these regions may suggest more solid organic materials than can be readily explained by atmospheric photochemical models. These issues will be discussed further at the meeting.

This work was carried out at JPL/Caltech under a contract with NASA.