Observed regions on Europa’s surface map (image credit: USGS Map-a-planet). The green and yellow areas were observed on 2019 May 17 and 18, respectively. The green region covers the southeastern region of the trailing hemisphere (210°–180°W, 20°–50°S) and the southwestern region of the leading hemisphere (180–110°W, 20–50°S). The yellow area covers the southern region of the trailing hemisphere (330°–190°W, 30°–60°S). The gray area covers a part of the northern regions of the trailing hemisphere (256° ± 5°W, 15° ± 14°N). The red area covers a part of the equatorial regions of the leading hemisphere (160° ± 9°W, 3° ± 15°N). The spectral data of two areas are used for the estimations for hydrated Cl-bearing salts (see detailed in Section 4). The regions outlined by thick black lines enclose chaotic terrains (Doggett et al. 2009).