The effort to save 33 men trapped deep in a Chilean mine was an unprecedented challenge, experts said today.
It means months of drilling, then a harrowing three-hour trip in a cage up a narrow hole carved through solid rock.
If all of that is successful, the freed men will emerge from the earth and "feel born again", said an American miner who was part of a group dramatically rescued in 2002 with similar techniques. But that rescue pulled men from a spot only one-tenth as deep.
"They're facing the most unusual rescue that has ever been dealt with," said Dave Feickert, director of KiaOra, a mine safety consulting firm in New Zealand that has worked to improve China's dangerous mines.
"Every one of these rescues presents challenging issues. But this one is unique."
First, engineers must use a 31-ton drill to create a "pilot" hole from the floor of the Atacama Desert down 2,200 feet to the area in the San Jose mine where the men wait.
Then the drill must be fitted with a larger bit to carve out a rescue chimney that will be about 26 inches wide - a task that means guiding the drill through solid rock while keeping the drill rod from snapping or getting bogged down as it nears its target.
Finally, the men must be brought up one at a time inside a specially built cage - a trip that will take three hours each. Just hauling the men up will itself take more than four days - if there are no problems.
"Nothing of this magnitude has happened before; it's absolutely unheard of," said Alex Gryska, a mine rescue manager with the Canadian government.
Mr Gryska said he was confident Chile's state-run Codelco mining company, with its vast expertise in the world's top copper-producing nation, would successfully drill the hole out.
But he said he was worried about the three to four months officials say it will take to do so - and the key role the miners themselves will play in their own rescue.
Chilean officials said the miners would have to remove more than 3,000 tons of rock as it falls into the area where they are trapped. There is little danger to the men - the area includes a shelter and about 500 yards of a shaft outside that. But as the rock starts to fall a month from now, the men will work in non-stop shifts to remove it with wheelbarrows and industrial sweepers.
"The thing that concerns me is welfare of workers, their mental state. That will be real tough," said Mr Gryska. "From a health perspective, it's hot down there. They're talking about working 24/7 in 85 degrees for two months. Their mental state for that work will be critical."
Early on, Chile's health minister Jaime Manalich said at least five of the men showed signs of depression. But spirits have improved with a supply of water, food, special clothes to keep them dry in damp conditions and the first verbal communication with loved ones this week.
Early today the government released another video of the miners that shows them smiling, shaved and wearing red T-shirts. The short video, which does not appear to have sound, is a stark contrast to previous videos that pictured the men shirtless and more subdued, with some getting emotional while recording a message for loved ones.
Earlier, Chilean officials met four "life sciences" specialists from Nasa in Santiago.
Michael Duncan, Nasa's deputy chief medical officer who is leading the team in Chile, said his group had been asked to provide help in nutrition and behavioural health.
Mr Duncan said his team saw two videos the miners made of themselves and their surroundings - and they clearly raised some concern about weight loss.
He said a priority was increasing the miners' calorie intake, getting them on a regular sleep schedule and ensuring they remained optimistic.
"These miners showed us tremendous strength in surviving as long as they did without any contact with the surface," he said.
"What we want to try to avoid is any kind of situation of hopelessness on the part of the miners."