"I'm exploring with colleagues whether sulfur compounds could work as solvents of life," Schulze-Makuch noted. Other possibilities include sulfur dioxide and sulfuric acid. While it is not especially efficient as a solvent for ions, it does dissolve many substances, including many organic compounds. Hydrogen sulfide is one choice, as it is reasonably abundant in Io's shallow subsurface and remains liquid from negative 123 to negative 76 degrees F (-86 to -60 degrees C), falling within the environmental conditions that would prevail there. The primordial soup that any life on Io might have originated from was likely based on water, but the solvent of choice for organisms there might have drastically changed later on as the moon transformed. Microbes are common in lava tubes on Earth, from ice and volcano zones in Iceland to hot sand-floored tubes in Saudi Arabia, and lava tubes are the most plausible cave environment for life on Mars, he added. The lava tubes also could provide thermal insulation, trapping moisture and providing nutrients such as sulfurous compounds. The many lava tubes thought to exist on Io could serve as an especially favorable environment for life, Schulze-Makuch suggested, by protecting organisms from radiation. Any organic compounds that once existed on the surface or that may today still emanate from the subsurface - which probably were naturally present in this region of space during Io's formation - would get quickly destroyed by Jupiter's radiation. At this point life could have retreated underground, where water might still be abundant, and geothermal activity and sulfur compounds could provide microbes with sufficient energy to survive.Īlthough no organic molecules have been detected on the moon’s surface, that does not mean they do not exist underground, Schulze-Makuch said. Jupiter's radiation would have stripped this water from Io's surface, perhaps within 10 million years. This photo was assembled from three black and white negatives by the Image Processing Lab at the Jet Propulsion Laboratory. Voyager 1 took photos of Jupiter and two of its satellites (Io, left, and Europa) on Feb. Io's heat, combined with the resulting possibility of liquid water, could have made life plausible. "We shouldn't categorize it as dead right away just because it's so extreme."Ĭomputer models suggest Io formed in a region around Jupiter where water ice was plentiful. "Life on the surface is all but impossible, but if you go down further into the rocks, it could be intriguing," he said. If life did ever develop on Io, there is a chance it might have survived to the present day, Schulze-Makuch suggested. Still, conditions on Io might have made it a friendlier habitat in the distant past. "Everyone right away tends to categorically exclude the possibility of life on Io," said astrobiologist Dirk Schulze-Makuch at Washington State University. In addition, no organic molecules have been detected on its surface, and it has only an extremely thin atmosphere devoid of detectable water vapor. Io is generally considered a poor candidate for life because of all the radiation Jupiter blasts it with. This means Io is a land of both fire and ice. Although the heat near the volcanoes can reach some 3000 degrees F (1649 degrees C), high enough to keep lava liquid, Io's surface temperature averages at about negative 202 degrees F (-130 degrees C), leading to sulfur dioxide snowfields. This extreme activity is the result of Jupiter's powerful gravitational pull, which causes Io's tormented solid crust to bulge up and down 328 feet (100 meters) or more, generating intense heat in Io due to friction. However, its extraordinarily volcanic sibling Io might be a possible habitat as well.Ī bit larger than Earth's moon, Io is the innermost of Jupiter's large satellites and the most volcanically active body in the solar system, with plumes of matter rising up to 186 miles (300 km) above the surface. When it comes to where extraterrestrial life might dwell in our own solar system, Jupiter's moon Europa often grabs the spotlight.
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