Volatile-rich earth-mass planets in the habitable zone

A small planet is not necessarily a terrestrial planet. Planets that form beyond the snow line with too little mass to seed rapid gas accretion (less than or similar to 10(+)) should be rich in volatile ices like H2O and NH3. Some of these planets should migrate inward by interacting with a circumstellar disk or with other planets. Such objects can retain their volatiles for billions of years or longer at similar to 1 AU as their thick steam atmospheres undergo slow hydrodynamic escape. These objects could appear in future surveys for extrasolar Earth analogs.