www.eas.org NEW EXPERIMENTAL STUDIES OF ICE GRAIN EJECTION BY MASSIVE GAS FLOW, IMPLICATIONS TO COMETS,

Abstract. Ice grains are ejected whenever gases are flowing from gas-laden amorphous ice upon its warming-up. We elucidated the mech-anism of gas trapping when flowing onto a gas-free ice layer. The observations on ice grain ejection from comets, Enceladus, Triton and the Martian South Polar region are explained as well. 1 Experimental procedures and results Two experimental setups were used to study ice grain ejection: (1) Thin ice sam-ples were produced by flowing water vapor and gases, either mixed together or separately, on to a cold plate at 50 K (e.g. Bar-Nun et al. 1987; Laufer et al. 2013). In the case of 100 µm layer of frozen CO2 covered by a 200 µm thick layer of amorphous ice, upon uniformly warming up the sample, ice grains and jets of gas were measured by a quadrupole mass filter (MS), at a msec time resolution; (2) Few cm thick gas laden amorphous ice layers were formed in a one of its kind machine (Bar-Nun et al. 2003). Alternatively, in this machine separate cm thick layers of frozen gas and water ice could have been deposited, one on the top of the other. The new experimental studies on thin (up to 200 µm) ice layers confirmed our previous findings (Bar-Nun et al. 1987) on ice grain ejection during the annealing of gas-laden amorphous ice and during its transformation into cubic ice. A mas-sive gas flow, from the interior, breaks the ice structure and is imbedded in the amorphous ice, to be released from it during its annealing and transformation to cubic ice as seen in Figure 1. A new millisecond time resolution revealed a huge flux of tiny ice particles emanating from the ice (Fig. 2)