How did it happen? The question has haunted Jeff Alley since he heard that six people climbing Washington's Mount Rainier last month, including his friend Mark Mahaney of St. Paul, were missing and presumed dead.

The climbers' bodies were not recovered, and their fate remains something of a mystery. For days, Alley "obsessed over it," and for good reason. He and his girlfriend, Ashley Melco, were scheduled to leave in just a few weeks to climb Mount Rainier themselves.

"Mark's passing, with the reminder of life being so vulnerable, definitely puts in perspective what we're doing," Alley said recently in his St. Louis Park home, as he and Melco packed for the expedition.

Mahaney, 26, was an "incredibly fit, incredibly strong ice climber — very smart, very intelligent in the way he climbed," Alley said. Despite his skills, and even though his group was led by two seasoned guides — one had reportedly climbed Rainier more than 50 times — something went wrong.

Suddenly, Alley and Melco found themselves thinking more about risk.

"You always know the risk factor is there, but I don't think we really got it," Alley said. "It sort of drove home the point."

Still, they didn't consider canceling the climb. They'd been preparing for the late-June adventure since January, acquiring equipment, training twice a week by donning 40-pound packs and clambering up and down from the Franklin Avenue Bridge.

To people who haven't done it, climbing may look "insane and crazy," said Jeff Engel, a climber for 25 years and a friend of Alley, Melco and Mahaney. Experienced climbers don't see it that way. One climbing blogger, comparing statistics from the Census Bureau and the American Alpine Club, calculated that a mountaineer is 10 times more likely to die in a traffic accident than while climbing.

"If you use common sense and approach it with the necessary tools and protection, it's probably safer than driving to work," Engel said. "You wouldn't say, 'Omigod, there was a horrible accident on 35W; I'm never going to drive that road again.' "

Calculating risk

To be sure, Alley and Melco were not facing as much risk as Mahaney had. "What we're doing is drastically different from what they were doing," Melco said.

Mahaney's group was ascending Mount Rainier's north face, a steep and heavily glaciated incline prone to harsh weather. "Nothing will be easy on this climb," Mahaney wrote on Facebook in April.

On May 28 the group radioed from a campsite somewhere around 12,800 feet — less than 2,000 feet from the summit — reporting snowy conditions. That was the last time they were heard from. Climbers below them on the mountain had seen the group earlier that day; the next day they were gone.

Three days later, a helicopter search picked up signals from buried avalanche beacons and found climbing and camping gear scattered amid snow and rock, more than 3,000 feet below where the radio call had come from.

The evidence suggested that an avalanche had swept the group down the mountain during the night. The terrain was considered too dangerous to land, so the search was called off, the bodies unrecovered.

"Knowing what we know about the route that Mark was killed on, I don't think I'd ever attempt it," Alley said.

The route that Alley and Melco picked is less treacherous, though strenuous. It requires hiking 18 snowy miles up a 40-degree incline, ultimately ascending 11,000 feet, or about two vertical miles, to the summit. Alley compared it to hiking from Plymouth to downtown Minneapolis while climbing to the height of 14 IDS Towers.

Mahaney had climbed their route last year and "was really excited for us to go," Alley said.

Even on their route, the mountain can pose dangers: avalanche, strong winds, bad weather, crumbling rock, crevasses.

"This is probably the most risky adventure I've ever taken," Alley said. "Even if you do everything correctly, you can still get injured, hurt, sent to the hospital."

After hearing about Mahaney, he and Melco took the extra precaution of acquiring GPS radios and signaling devices. Alley envisioned how these might come in handy in an accident, such as a fall into a crevasse. "If I land OK, I can get my radio and say, 'Hey, I'm OK.' "

"So worth it"

Alley, 34, and Melco, 20, met while climbing. Melco compares the sport to yoga: "the body awareness, balancing, using your core, concentrating." Alley likens it to chess: "You're reading the wall and figuring out what moves the mountain is going to let you have."

Alley, who holds a geology degree and works as a customer service agent and a freelance photographer (www.adventurealleyphotography.com), has been rock climbing since high school, and ice climbing for eight years, but Rainier will be his first mountain.

He has studied the peak — the country's 17th-highest in elevation, but the most "topographically prominent" in the Lower 48 (meaning roughly, its summit is farthest above its base) — through books, maps and videos. He knew that standing at the top, one can see for up to 150 miles. "I'm looking forward to that sunrise," he said.

Melco, a recent University of Minnesota graduate planning to attend veterinary school and a self-described "adrenaline junkie," has more mountaineering experience. On her first mountain climb, in Colorado, her partner sprained his ankle near the top. They crept back down, ran out of food and water, became dehydrated, felt themselves "hallucinating from malnutrition," and finally limped into camp long after dark.

"It was so exhilarating we did it some more," she said. At the summit, she had gazed out at a glassy glacial lake and thought, "OK, this is so worth it."

Going for the journey

Eighty-nine people have died while trying to climb Mount Rainier between 1897 and 2011. That might seem like a lot, but it's fewer than have died in the adjoining national park of other causes. Still, it's a challenging climb. Of the 8,000 to 13,000 people who attempt it each year, only about half make it to the top.

Alley and Melco have daydreamed about reaching the summit, but emphasized that's not the reward of the climb. "We're going for the journey to get there," Melco said. They were prepared to turn around if continuing upward seems dicey.

"Sometimes it's a bigger challenge to just say no," she said.

"If the weather's good, we'll have a good shot at it, and if the weather's crappy I want to go home," Alley said. "It will still be there."

Indeed, after the 18-mile effort, the summit, however beautiful, might seem a little anti-climactic, they said.

"You spend maybe a couple of hours at the top, taking pictures, hooting and hollering," Alley said.

"If we need a couple of hours," Melco added.

Then they would head back down.

If luck is on their side, by the time you read this, they will have completed their five-day expedition.

Katy Read • 612-673-4583