The icy worlds in our Solar System (e.g. Europa, Enceladus, Ceres, Triton and Titan) possess surface organics, and possibly subsurface oceans, so are prime astrobiological targets in the search for Life. Space missions to these icy worlds have been the key to measuring their surface composition and assessing their subsurface composition through measurements of their outgassing plumes. However, the composition of the water ice and other organic and inorganic materials residing on the surfaces of these icy worlds, as well as their subsurface regions, including the putative internal oceans, can also be studied by Earth-based astronomical observations.
Among the many small icy solar-system bodies, recently water vapor from Ceres was detected by Herschel infrared space telescope and circumstantial evidence of the existence of water plumes from Europa via observations by Hubble space telescope was also reported. Ceres is the largest celestial body in Main Asteroid Belt and is also the sole dwarf planet in the inner solar system. Europa, on the other hand, is the 6th largest moon in the Solar System and the smallest Galilean moon of Jupiter. Data taken from Dawn spacecraft suggest that a subsurface layer of briny water ice, together with ammonia-rich clays, may exist on Ceres. Similar to another icy moon, Enceladus of Saturn, a global subsurface ocean was also inferred to exist below the ice crust of Europa from the diversity of surface geological features and the magnetic field measurements made by the Galileo spacecraft. We have hence observed with the 15-m James Clerk Maxwell Telescope (JCMT) and Atacama Large Millimeter/submillimeter Array (ALMA) to look for molecular emission in both Ceres’ and Europa’s exospheres. We will present preliminary results from our observations and discuss their astrobiological implications.