Mar. 13, 2024 — A deeply eroded giant volcano, active from ancient through recent times and with possible remnants of glacier ice near its base, had been hiding near Mars' equator in plain sight.

This was a year whose high points included Joan Jonas’s luminous survey, the extravaganza “PST ART,” and the 24-karat beauty of a show “Siena: The Rise of Painting, 1300-1350.” By ...