"Why do you want to climb Mount Everest?"

"Because it's there."

So answered 37-year-old explorer George Mallory to a reporter's question before the third British Mount Everest Expedition, in 1924. Some 30 years before Sir Edmund Hillary made it to the top, Mallory, in his third attempt to scale Everest, would disappear along with his climbing partner Andrew "Sandy" Irvine somewhere high on the North East Ridge of the world's highest mountain.

Their fate was unknown for 75 years, until contemporary explorer Conrad Anker discovered Mallory's body in 1999. Did Mallory make it to the top? Would Anker? And why did Anker go back to Everest eight years later?

These and other questions are tackled in The Wildest Dream: Conquest of Everest, the new IMAX film opening Friday at the Houston Museum of Natural Science. The documentary mixes archival and newsreel footage of Mallory's climb with Anker's two ascents of Everest, the highest place on earth at 8,850 meters (29,035 feet). Anker provides commentary throughout.

Letters between Mallory and his wife are also read to give the project an additional personal touch. The IMAX format gives the viewer many incredible vantage points, particularly at the summit of Everest, where one is taken above the clouds and the other mountain peaks which make up the Himalaya range in Tibet, between India and China.

Produced and directed by Anthony Geffen, Conquest of Everest is narrated by Academy-Award-nominee Liam Neeson. Also featured are the vocal talents of Hugh Dancy, Alan Rickman, and most movingly, Ralph Fiennes and Natasha Richardson, who are heard reading the letters between George Mallory and his wife Ruth. (The movie is dedicated to Richardson, Neeson's late wife.)

Anker, an American who lives in Bozeman, Mont., came to Houston to promote the film. He told me that he was asked in 1999, with two weeks' notice, to join an expedition to search for the remains of Mallory and Irvine on Everest. An experienced climber with expeditions to Alaska and Antarctica under his belt, Anker took on the challenge. He was 37, he same age as Mallory when he died.

I asked how one gets up the nerve to take on something like Everest.

"I'm a practiced climber," he said. "Even so, one still has to have a certain degree of self-confidence."

The 1999 Everest explorers knew only that Mallory had been last spotted some 800 feet below the summit. As Anker's fate would have it, he would be the one to find Mallory's well-preserved remains, clad in gabardine and hobnailed boots. Mallory, a devoted family man with three children, was known to have carried a picture of his wife Ruth; he had promised her that he would leave it at the summit of Everest. However, no picture was found on his body, which raised more questions: Had he lost it? Or had he already been to the summit and was on the descent when he died?

Still searching for answers, and perhaps in hope of finding the missing Sandy Irvine, Anker led his own team back to Everest eight years later, in 2007. He wanted to replicate Mallory's expedition as closely as possible, including retracing the North East Ridge Route near the summit. He even had the ladder removed from the infamous 90-foot sheer rock wall known as the "Second Step" to free-climb it, just as Mallory and Irvine would have had to do 83 years earlier.

Mallory had led an interesting life even before he took on Everest. Born in Great Britain (Mobberley, Cheshire), he was the son of a clergyman. He was introduced to rock climbing and mountaineering while still a teenager by a schoolmaster who took a group of people on an annual trip to the Alps. In 1905 he entered Magdalene College, Cambridge, and became good friends with members of the Bloomsbury Group. He was an excellent oarsman who rowed his three years at Cambridge.

After graduation, he taught for a few years in Surrey (interrupted by World War I military service); he married, yet still found time for recreational climbing. He would meet the poet Robert Graves and was even best man at his wedding. Mallory would resign his teaching position to join the first Everest expedition in 1921.

Besides spending time mountaineering and exploring, Anker is a lecturer and author. He was previously involved in production of the films Shackleton's Antarctic Adventure (2001), about the famous British explorer; Light of the Himalaya (2006), about natives of the region who suffer from the planet's highest rates of cataract blindness; and The Endless Knot (2007), Anker's personal story of surviving a Himalaya avalanche which took the life of his climbing partner and best friend, Tony Lowe.

Anker's now married to Lowe's widow Jennifer, and adopted and is raising Lowe's three boys. I asked how the boys were doing in light of Lowe's tragedy, and the fact that their stepfather is still on mountain expeditions.

"The boys are doing just great," Anker said proudly. "They know that climbing is just what daddy does."

Are any of them looking at climbing as a career? "Not seriously. Not yet, anyway. They like sports, all kinds of activities. The youngest is in ninth grade. Plenty of time to make up his mind about what he wants to do."

Almost stealing the show from Mallory, Anker, and the breathtaking IMAX vistas in Conquest of Everest is Leo Houlding, a British climbing prodigy who went along with Anker on the 2007 expedition at the tender age of 22.

"I've known Leo since he was a teenager. He didn't have any real climbing experience at 'altitude' but he turned out to be a natural," Anker said.

What was the coldest temperature on the mountain?

"About -18 degrees Celsius, or 0 degrees Fahrenheit, before the wind factor. Frankly, I've experienced colder temperatures in Montana. But when you add the wind, and the thin air...above 26,000 feet on Everest it's call the 'Death Zone' and most climbers are on oxygen...for that climb, I started my trip from the U.S. in early April, spent several weeks at base camp, followed by advanced base camp, and in mid-June we spent about a week on the ascent. The descent was much faster, just two to three days."

I asked Anker how the press tour was going. "It's doing well on the museum circuit, on the IMAX screens around the country, and kids especially seem to like it. Conquest did have a limited theatrical run last summer, but it opened on August 8th, the same weekend as Angelina Jolie's Salt, which had a marketing budget twice the amount of our total budget."

Sheer rock faces, snow, ice, wind, avalanches, thin air? That's no challenge to your average mountain climber, compared to taking on Angie.