WASHINGTON—Oxygen accounts for about 21 percent of Earth’s air, with the rest of our atmosphere primarily nitrogen. And most living things—including people, as we well know—need oxygen to survive.
Earth’s planetary neighbor Venus offers quite a different story. Its thick and noxious atmosphere is dominated by carbon dioxide—96.5 percent—with lesser amounts of nitrogen and trace gases. Oxygen is nearly absent. In fact, with Venus getting far less scientific attention than other planets such as Mars, the direct detection of its oxygen has remained difficult.
