White Mars: A new model for Mars' surface and atmosphere based on CO2

A new model is presented for the Amazonian outburst floods on Mars. Rather than the working fluid being water, with the associated difficulties in ach ieving warm and wet conditions on Mars and on collecting and removing the w ater before and after the floods, instead this model suggests that CO2 is t he active agent in the "floods." The flow is not a conventional liquid floo d but is instead a gas-supported density flow akin to terrestrial volcanic pyroclastic flows and surges and at cryogenic temperatures with support fro m degassing of CO2-bearing ices. The flows are not sourced from volcanic ve nts, but from the collapse of thick layered regolith containing liquid CO2 to form zones of chaotic terrain, as shown by R. St. J. Lambert and V. E. C hamberlain (1978, Icarus 34, 568-580; 1992, Workshop on the Evolution of th e Martian Atmosphere). Submarine turbidites are also analagous in the flow mechanism, but the martian cryogenic flows were both dry and subaerial, so there is no need for a warm and wet epoch nor an ocean on Mars. Armed with this new model for the floods we review the activity of volatile s on the surface of Mars in the context of a cold ice world-"White Mars." W e find that many of the recognized paradoxes about Mars' surface and atmosp here are resolved. In particular, the lack of carbonates on Mars is due to the lack of liquid water. The CO2 of the primordial atmosphere and the H2O inventory remain largely sequestered in subsurface ices. The distribution o f water ice on modern Mars is also reevaluated, with important potential co nsequences for future Mars exploration. The model for collapse of terrain d ue to ices that show decompression melting, and the generation of nonaqueou s flows in these circumstances may also be applicable to outer Solar System bodies, where CO2, SO2, N-2, and other ices are stable. (C) 2000 Academic Press.