Abstract
The habit and the growth feature of small ice crystals formed in a free fall state in high- and low-pressure helium and argon gases at the temperatures of -7 and -15°C were studied experimentally. It is found that the habit and the growth feature of small ice crystals in the range of about 20 to 50μm depend not only on the temperature and the degree of supersaturation but also on the kind and the pressure of the carrier gas and the size of crystals when small ice crystals were formed at water saturation. It is found that the dependence of the habit of small ice crystals on temperature is more emphasized under a high pressure but has a tendency to vanish under a low pressure. In high-pressure gas, ice crystal shapes which have never been observed in the earth's atmospheres are found. Such ice crystals may form in the atmospheres of Jupiter and Saturn where pressures are higher than that of the earth.
