With a key federal tax incentive about to expire, the U.S. installed a 5.5 gigawatts of wind power in December to cap off a year that saw a record 13.2 gigawatts of wind energy come online, according to a report released Friday by research firm Bloomberg New Energy Finance.
Impact craters surrounding the cap appear to be filled with ice and dust that was either deposited by wind or condensation, or perhaps further remains from an earlier larger ice cap.