In the past, a great deal of planetary research was basically descriptive, consisting of visual observations and photography. Beginning in the 1960s, a new generation of planetary scientists began to apply the techniques of modern astrophysics and geophysics to the study of the solar system. Inspired in part by the developing space programs of the United States and the Soviet Union, scientists began to ask more quantitative questions: What are the surfaces and atmospheres made of? What are the temperatures and wind speeds? Exactly what quantities of different elements and isotopes are present? And how can these new data be used to infer the origin and evolution of the planets? [Illustration: The major features of Jupiter are shown in schematic form. The planet is a banded disk of turbulent clouds; all its stripes are parallel to the bulging equator. Large dusky gray regions surround each pole. Darker gray or brown stripes called belts intermingle with lighter, yellow-white stripes called zones. Many of the belts and zones are permanent features that have been named. One feature of particular note is the Great Red Spot, an enigmatic oval larger than the planet Earth, which was first seen more than three centuries ago. During the years the spot has changed in size and color, and it escaped detection entirely for nearly fifty years in the 1700s. However, since the mid-nineteenth century the Great Red Spot has been the most prominent feature on the face of Jupiter. [2935]] N North polar region North north north temperate belt North north temperate zone North north temperate belt North temperate zone North temperate belt North tropical zone North equatorial belt Equatorial zone equatorial band South equatorial belt N. component S. component South tropical zone Great Red Spot South temperate belt South temperate zone South south temperate belt South south temperate zone South polar region S Wildt had already suggested the basic gases in the atmosphere of Jupiter: primarily hydrogen and helium, with much smaller quantities of ammonia and methane. Undetected but possibly also present were nitrogen, neon, argon, and water vapor. The abundance of helium was particularly a problem; although it was presumably the second-ranking gas after hydrogen, it has no spectral features in visible light and its presence remained only a hypothesis, unconfirmed by observation.