The planet’s divergent path includes “loss of habitability, loss of water on the surface, sulfuric acid clouds, and a dense carbon-dioxide atmosphere,” Meadows said. “Venus gives us an example of an alternative evolution for planets,” said Vikki Meadows, an astrobiologist who heads the Virtual Planetary Laboratory in NASA’s Nexus for Exoplanet System Science. Venus is a kind of negative to Earth’s positive by studying what went so very wrong, we might learn what it takes to get life right. Yet Venus also exerts an irresistible pull for astrobiologists – scientists who study how life begins, its necessary ingredients and the planetary environments that it might require. A runaway greenhouse effect likely boiled off Venus’s oceans and turned the planet into a perpetual inferno – the hottest world in the solar system. But the two planets took very different paths. Venus began its existence much as Earth did, perhaps even with globe-spanning oceans. Often called our “sister planet,” Venus, of similar size and structure to Earth, has critical differences: a surface hot enough to melt lead, a crushingly heavy atmosphere and an extremely volcanic geology. Let’s begin the tour with our hottest planet. Jupiter’s Europa and Saturn’s Enceladus, despite their frozen, forbidding surfaces, are hiding vast oceans beneath the ice – among several moons with subsurface oceans. There’s Mars, now a cold, nearly airless desert, but once temperate and flowing with water.Īnd much hope remains out among the gas giants – not the big planets themselves, but their long list of moons. That brings us back to those tantalizing prospects. Same for dwarf planet Ceres in the asteroid belt, considered a possible “water world” either now or earlier in its history. The farthest provinces, with their dwarf planets and would-be comets locked in deep freeze, also seem a poor bet, though they can’t be ruled out. ![]() The same goes for the cloud-covered gas giants, with their crushing atmospheric pressures and seemingly bottomless depths – perhaps no solid surface at all, or if there is one, it’s no place for any living being. The broiling inner solar system seems unlikely (though the high-altitude clouds of Venus remain a possibility). ![]() Still, NASA continues searching the solar system for signs of life, past or present, and decades of investigation have begun to narrow down the possibilities. “Otherwise, we would have likely detected it.” “There’s nothing else in the solar system with lots of life on it,” said Mary Voytek, senior scientist for astrobiology at NASA Headquarters in Washington, D.C. In between are a few tantalizing prospects for life beyond Earth – subterranean Mars, maybe, or the moons of giant planets with their hidden oceans – but so far, it’s just us. De La TorreĪ tour of our solar system reveals a stunning diversity of worlds, from charbroiled Mercury and Venus to the frozen outer reaches of the Oort Cloud. Illustration: NASA/JPL-Caltech/Lizbeth B. A few show signs of potential habitability. The planets and moons of our solar system, some seen in this illustration, are extroardinarily diverse.
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