early spacecraft images to be volcanic (or non-impact) in origin. In September 2007, the International Astronomical Union (IAU) renamed the volcano Alba Mons (Alba Mountain), reserving the term Alba Patera for the volcano's two central depressions (calderas). Nevertheless, the entire volcano is still commonly called Alba Patera in the planetary science literature. The term Alba is from the Latin word for white and refers to the clouds frequently seen over the region from Earth-based telescopes. The volcano was discovered by the Mariner 9 spacecraft in 1972 and was initially known as the Alba volcanic feature or the Arcadia Ring (in reference to the partial ring of fractures around the volcano). The IAU named the volcano Alba Patera in 1973. The volcano is often simply called Alba when the context is understood. Location and size Alba Mons is centered at in the Arcadia quadrangle (MC-3). Much of the volcano's western flank is located in the adjacent Diacria quadrangle (MC-2). Flows from the volcano can be found as far north as 61°N and as far south as 26°N (in the northern Tharsis quadrangle). If one takes the outer margin of the flows as the volcano's base, then Alba Mons has north–south dimensions of about and a maximum width of . It covers an area of at least 5.7 million km2 and has a volume of about 2.5 million km3. The volcano dominates the northern portion of the Tharsis bulge and is so large and geologically distinct that it can almost be treated as an entire volcanic province unto itself. Although Alba Mons reaches a maximum elevation of above Mars’ datum, the elevation difference between its summit and surrounding terrain (relief) is much greater on the north side of the volcano (about ) compared to the south side (about ). The reason for this asymmetry is that Alba straddles the dichotomy boundary between the cratered uplands in the south and the lowlands to the north. The plains underlying the volcano slope northward toward the Vastitas Borealis, which has an average surface elevation of below datum (-). The southern part of Alba Mons is built on a broad, north-south topographic ridge that corresponds to the fractured, Noachian-aged terrain of Ceraunius Fossae (pictured left). Physical description Alba's size and low profile makes it a difficult structure to study visually, as much of the volcano's relief is indiscernible in orbital photographs. However, between 1997 and 2001,