Nuclear spectroscopy is a powerful technique that uses measurements of gamma-rays and neutrons to characterize the elemental composition of a wide variety of materials, including rocks, metals, and ices. This technique has been applied to orbital observations of a wide variety of objects, including asteroids (1 Ceres [1], 4 Vesta [3], and 433 Eros [3,4]), planets (Mercury [5-7], Venus [8], and Mars [9]), and the Moon (e.g. [10]). Those successes paved the way for a new generation of planetary nuclear spectroscopy investigations, including the first ever investigation of a metallic world (the asteroid 16 Psyche [11]), the first dedicated investigation of Mars’ moons (Phobos [12]), and a rotorcraft-based investigation of Saturn’s icy moon Titan [13]. 

I will present a short historical overview of completed nuclear spectroscopy investigations, highlighting discoveries at asteroids 433 Eros and Mercury. I will then show how these results enable the new investigations that seek to answer outstanding questions in planetary science. For example, nuclear spectroscopy of the metallic asteroid 16 Psyche – thought to be an exposed planetary core – may provide insights into the chemical composition of planetary cores. Additionally, nuclear spectroscopy of Phobos will resolve longstanding questions about the formation of Mars’ moons by differentiating between formation via asteroid capture or giant impact on Mars.

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