society, for science, and for NASA's missions. These examples are not meant to be typical of all R&DA grants, nor—for disciplines that span the interests of more than one federal agency—do they necessarily represent spheres of NASA leadership, but they do illustrate how modest R&DA investments make a significant difference.
R&DA projects occasionally inform policy debates about issues of national importance or change the way we live or work. Two examples of the former and one of the latter are presented in this section. In the first, results from R&DA research have helped provoke political action; in the second, emerging technologies have stimulated R&DA research in anticipation of political interest; and in the third, products of R&DA-funded research have contributed to understanding the linkages between El Niño, the Southern Oscillation, and global weather, and consequently to developing regional crop strategies in agribusiness. Box 2.1 contains additional examples of this type.
1. Discovery And Diagnosis Of The Antarctic Ozone Hole, A Major, Unanticipated Surprise For Scientists, Caused Significant Changes In Public Policy.
The annual cycle of ozone in the stratosphere over the Antarctic has been tracked by scientists beginning with projects that were part of the International Geophysical Year in 1957. In the late 1970s, an unexplained deficit emerged in the total ozone amount in late-winter observations. In 1985, the British Antarctic Survey reported for the first time that dramatic decreases were occurring in the ozone concentration over Halley Bay and that the degree of ozone loss was worsening as the decade progressed. Theories of the cause of this unprecedented loss were put forward by serious scientific research groups in an international effort to diagnose the reason for this alarming development. In one example, investigators applied models that had been developed under a NASA R&DA project to study the upper-atmospheric photochemistry of Venus and Mars. There were several expeditions to gather more information and, in August and September 1987, NASA contributed an R&DA-funded airborne survey. An ER-2 aircraft flew from Punta Arenas, Chile, to penetrate the region of the stratosphere where ozone was disappearing. The key results are shown in Plate 2.1.
The mission demonstrated unequivocally that ozone was destroyed by chlorine and bromine radicals. The case linking chlorofluorocarbons (CFCs), the molecules that transport chlorine to the stratosphere, to the destruction of ozone over the Antarctic rests on three discoveries from this NASA mission. The first discovery was that the continental-scale region of severe ozone depletion was isolated from the rest of the stratosphere by the polar night jet, which creates a continental-scale ''containment vessel." The existence of this barrier preventing exchange is shown clearly by the high-resolution aircraft data in Figure 2.1. The second discovery was the anticorrelation between O3 and ClO that occurs within this stratospheric containment vessel. Plate 2.1 shows that on August 23, 1987, as sunlight returned to the region, O3 had emerged from the polar night largely unaffected. Three weeks later, on September 16, ozone had eroded sharply in the presence of high ClO concentrations within the sunlit containment vessel. The third discovery emerged from R&DA-funded laboratory studies that determined the rates of key reactions responsible for the destruction of ozone by chlorine and bromine radicals in sunlight.
When taken together, the three elements in this case—each of which has appeared in and been critiqued in the international scientific literature—provide irrefutable evidence that the dramatic reduction in stratospheric ozone over the antarctic continent would not have occurred had CFCs not been