Frontier of Planetary Science Revealed by Terahertz Wave Observations in Deep-space Explorations

Abstract

Terahertz waves have been utilized for new and/or better understandings of the earth and planetary sciences through observations of atmospheric molecules and the physical properties of surfaces, but applications in the field of planetary science using observations from terahertz instruments on board spacecraft going into deep space are still at the initiation stage. In this review paper, we describe the scientific achievements of Rosetta/MIRO, which was the first terahertz instrument on board a deep-space spacecraft for the observation of the nucleus of comet 67P/Churyumov-Gerasimenko, the expected scientific achievements of JUICE/SWI, which will be launched to observe Jupiter and its icy satellites, and expectations for a future terahertz instrument on a Mars orbiter. Keeping in mind these achievements and expectations, we discuss the expansion of planetary science allowed by the observations made by terahertz instruments on board deep-space spacecraft.