Ice Layers Origins in Icy Satellites and Icy Giants

Icy giant planets such as Uranus and Neptune are believed to have differentiated into three primary sections: an atmosphere of helium, methane gas, and molecular hydrogen; an ``icy'' mantle of water, ammonia, and methane; and a core of rock and iron. Icy satellites of the gas giant planets Jupiter and Saturn are also thought to have layers of ices that include carbon monoxide and carbon dioxide, although at reduced pressures and temperatures. Here we investigate ammonium bicarbonate (NH4)HCO3, which degenerates to water, carbon dioxide and ammonia between 36 and 60 °C at room pressure. We performed quasi-hydrostatic high-pressure diamond-anvil cell (DAC) experiments up to 30 GPa over a range of temperatures (22 to 150 °C). Preliminary analysis shows that ammonium bicarbonate not only breaks down to its icy components with increased temperature, but also at increased pressures of ~2 GPa. The individual reaction components reformed into ammonium bicarbonate upon pressure quenching for unheated samples.