The Atlantic‘s David Brown wonders why NASA is neglecting the study of Venus, arguably the most Earth-like world known to us.
A generation has now gone by since the agency set a course for the second planet from the Sun, and with this latest mission opportunity lost, the earliest an expedition there might launch (from some future selection process) would be 2027—nearly 40 years since our last visit.
For centuries, it would have been inconceivable that Venus would be in such a predicament. In the 18th century, Venus was the organizing force in international science. When humanity was finally able to stretch its arms toward the solar system, the first place it reached for was Venus. It was our first successful planetary encounter beyond Earth, and was the first planet on which humans crashed. It would later would host our first graceful landing.
Venus and Earth are practically twins. They’re alike in size, density, gravity, and physical makeup. They are both in our star’s habitable zone. Scientists have discovered no other adjacent planets in the entire galaxy that share such similarities. And yet somewhere along the way, Earth became a cosmic paradise for life as we know it, and Venus became a blistering hellscape. Beneath its sienna clouds of sulfuric acid is the greenhouse effect gone apocalyptic. At 850 degrees Fahrenheit, its surface is hotter than Mercury, though the planet itself is much farther from the Sun. A block of lead would melt on the surface of Venus the way a block of ice melts on Earth.
In recent years, the Kepler space telescope has discovered more than 3,000 planets around other stars, many of which are orbiting in habitable zones where water could be stable on a planet’s surface. These “Earth 2.0’s” are but pixels of light many light years away and are difficult to study. Conveniently, there is an Earth 2.0 next door to our own. Venus was an ocean world for much of its history. By understanding that history, how it compares to Earth, and how it lost its habitability, we might better understand potentially habitable exo-worlds.
Moreover, as scientists and lawmakers grapple with climate change, they can look to Venus. “I don’t want to say that Earth can turn into Venus from global warming,” says Bob Grimm, the director of the Department of Space Studies at the Southwest Research Institute and chair of the Venus Exploration Analysis Group. “That is not going to happen. It takes a lot of carbon dioxide to make Venus’s atmosphere as hellish as it is. But that lies on a continuum, on a spectrum, of how CO2 in atmospheres affect planetary climates. Earth is not going to turn into Venus, but Venus has lessons on climate evolution for Earth that we should pay attention to.”