Solar System Smackdown: Mars Vs. Venus One of the fiercest hunts in the solar system is the scientific search for signs of extraterrestrial life—whether that’s in a methane ocean on Titan, under the icy crusts of Europa or Enceladus, in newly discovered subsurface salty lakes of Mars or, in the case of hypothetical long-dead fossils, in the rocks of ancient Martian river deltas. But just as the next Mars rover—equipped with life-sensing instruments of all kinds—is barreling toward the Red Planet for a February landing, comes news from another planet. A research team writing in Nature in September say they’ve found high concentrations of phosphine in the atmosphere of Venus. That much phosphine is not known to exist without help from bacteria—and researchers dating all the way back to Carl Sagan have suggested that the thick, acidic clouds of Venus would be a plausible place to harbor microscopic, extreme-loving life. Is this a good reason to send more missions to Venus? Or is Mars still the best candidate for investment of finite resources? Science Friday producers Katie Feather and Christie Taylor host this completely made-up argument about which planet is the best bet for finding life, with help from genetics and astrobiology researcher Jaime Cordova, and planetary scientist Briony Horgan. A Breakthrough In A Mollusk Mystery Freshwater mussels in the United States are having a bad time. It’s estimated that 70 percent of freshwater mussel species in North America are extinct or imperiled—a shocking number.  There’s a good chance you haven’t heard about this. Mussels aren’t the most engaging creatures, and they don’t pull at the heartstrings like easy anthropomorphised mammals. These mussels also aren’t the ones that wind up on a restaurant’s seafood platter. But mussels play an extremely important role in aquatic ecosystems, so scientists are doing their best to figure out what’s going on with their drastically declining populations.  Scientists recently discovered 17 viruses present in mussels in the Clinch River, a waterway in Tennessee and Virginia, where about 80,000 mussels have died since 2016. This is a huge breakthrough in a mystery that has plagued researchers for years—though it may just be one piece of evidence for a multi-dimensional decline. Joining Ira to talk about mussels in trouble are Jordan Richard, a fish and wildlife biologist for the U.S. Fish and Wildlife Service in Madison, Wisconsin, and Eric Leis, a parasitologist and fish biologist at the La Crosse Fish Health Center in La Crosse, Wisconsin.