Photos: 2013 Iditarod Trail Invitational

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Scott Wilkinson of the U.K. pedals along open water on the Yentna River Monday during the Iditarod Trail Invitational. A snow drought in the early winter combined with a bitter cold snap froze the Yentna and Susitna rivers in ways never seen before. The Iditarod Trail north has to weave around a fair bit to avoid open leads and overflow.

The 2013 Iditarod Trail Invitational kicked off Feb. 24, with 50 people on foot, bicycles or skis heading out into the Alaska wilderness. The bulk of them are from Europe or the Lower 48, traveling 350 to 900 miles along the Iditarod Trail from the abandoned port of Knik to McGrath and then Nome.

Most people opt for the 350-mile version of the trip. A few, however, do keep going. Less than four dozen have made it all the way to Nome at the north end of the trail in the past decade. More people annually complete the Iditarod Trail Sled Dog Race, which begins a week after the Invitational's start. A handful of the racers harbor thoughts of winning the Invitational, which boasts neither trophies nor prize money: Most of them will be competing solely with themselves.

The Invitational, which limits the field to 50, turns away potential entrants every year. Race organizers Bill and Kathi Merchant reject some as just not mentally ready to tackle the Alaska wilderness. Others may lack the physical toughness necessary to haul food and equipment north along the trail.

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