Spectral Variations across Latitudes on Asteroid (3200) Phaethon

Abstract 3200 Phaethon is a near-Earth asteroid known to be actively emitting dust and gas when near its perihelion, and it is the target of the Japanese DESTINY+ mission. Several visible–near-IR spectra were obtained of Phaethon during 2003–2017, which have been collected together and analyzed with respect to its shape model. Using a thermal model, we examine the diurnal temperature variations across Phaethon’s surface (Δ T ∼ 600 K). We find different solar radiation heating between the north and south regions, with very high surface temperatures in the south region (max peak ∼ 1050 K), while a lower temperature is found in the north region (a mean value of 760 K). Our analysis of the photometrically corrected slope suggests a latitudinal trend in surface composition. We propose that the northern region of Phaethon may be linked to unusual chondrites and naturally heated Y-82162 samples (63–125 μ m and/or chips), while the southern region shows similarities to Ivuna CI chondrites heated to 700°C (0–125 μ m). The equatorial region appears to include a mixture of materials from both hemispheres.