On 16 March 2012, 52 Greenpeace activists from five different countries boarded Fennica and Nordica, multipurpose icebreakers chartered to support Shell's drilling rigs near Alaska. Around the same time period, a reporter for Fortune magazine spoke with Edward Itta, an Inupiat Eskimo leader and the former mayor of the North Slope Borough, who expressed that he was conflicted about Shell's plans in the Arctic, as he was very concerned that an oil spill could destroy the Inupiat Eskimo's hunting-and-fishing culture, but his borough also received major tax revenue from oil and gas production; additionally, further revenue from energy activity was considered crucial to the future of the living standard in Itta's community.

Answer this question, if possible (if impossible, reply "unanswerable"): How many Greenpeace activists boarded Fennica and Nordica in March 2012?
52