"People talked before about life in Venus' atmosphere, but they never thought through what that would mean," Seager said. Eventually, the droplets would grow too large and fall into the lower atmosphere, beginning the cycle anew. During their time aloft, the microbes could grow and reproduce, potentially living in these droplets for hours to months to even years. The spores could then attract droplets of fluid around themselves, much as dust and potentially microbes do in Earth's atmosphere, and return to active life. Updrafts could pull spores up from this haze depot to more temperate layers of the atmosphere. In order to survive the heat of the lower atmosphere, the microbes would have to go dormant, becoming inactive, dessicated spores that could better resist their hazardous surroundings.Īn artist's depiction of lightning in the atmosphere of Venus. The researchers suggested that Venusian microbes could fall into this haze layer and stay there, suspended in the air, just as similarly-sized haze particles have. "There's a lot we don't know about Venus." "People don't really know why this haze layer is there," Seager said. (In comparison, the average human hair is about 100 microns wide.)
Scientists don't know what particles make up the haze, just that they measure between 0.4 to 4 microns wide. Prior work found that below the lowest clouds of Venus, at altitudes of 29.5 to 20.5 miles (47.5 to 33 kilometers), is a layer of mysterious haze. Now Seager and her colleagues have discovered a scenario in which hypothetical microbes could survive in the skies of Venus, escaping a fate where they rain down onto the planet's hellish surface to die. And although such a tumble is rarely a problem for airborne microbes on Earth, it would likely prove deadly to Venusian life. But such cloud droplets repeatedly merge and grow, eventually getting large enough they fall out of the atmosphere. In the skies of Venus, the researchers determined, life would likely need to shelter within cloud droplets.
"Microbial life does not stay up there permanently, but it can get transported up and stay a week or two before coming back down again." Although such a possibility might seem far-fetched, "Earth itself has an aerial biosphere," study lead author Sara Seager, a planetary scientist at the Massachusetts Institute of Technology, told.
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