Strange circles have once again appeared in the frozen surface of Lake Baikal in Siberia, as spotted by astronauts aboard the International Space Station this April. News reports described the ice rings as a puzzling phenomenon. But experts say they can explain the mystery, and it's not aliens - methane gas rising from the lake floor represents the likely culprit. Methane emissions can create a rising mass of warm water that begins swirling in a circular pattern because of the Coriolis force, or the phenomenon caused by the Earth's rotation that also helps create cyclones. "Once the water mass reaches...