Two Americans won the Nobel Prize in medicine Monday for discovering how people can recognize an estimated 10,000 odors, from spoiled meat to a lover’s perfume.

Dr. Richard Axel, 58, of Columbia University, and Linda B. Buck, 57, of the Fred Hutchinson Cancer Research Center in Seattle, revealed odor-sensing proteins in the nose and traced how they send their information to the brain.

The Nobel Assembly at the Karolinska Institute in Stockholm, Sweden, said it chose the pair for the $1.3 million prize not because of any practical payoff from the work, but simply because they enhanced understanding of “the most enigmatic of our senses.”

For two scientists to single-handedly map one of the major human senses is unique in the history of science, Nobel assembly chairman Goeran Hansson said.

“It’s pretty amazing to be able to sit here in the 21st century and reward discoveries that explain one of the human senses,” he said.

Buck said she had not even known she was under consideration. “People have said things like, ‘You should win the Nobel Prize,”‘ she said. “I feel very honored, of course.”

Axel said sharing the prize with Buck was “a joy and a deep honor. … I’m very surprised and very happy.” He also said that the work might ultimately help scientists develop better insect repellants to keep away mosquitoes that transmit malaria, for example.

In 1991, Axel and Buck jointly reported discovering a large family of genes devoted to producing different odor-sensing proteins, called receptors, in the nose. Before that, scientists could only guess at how many different receptors were needed to distinguish smells in the environment.

Scientists now know that people have some 350 to 400 types of odor receptors. When the brain notes which receptors are activated, it interprets this pattern as a smell.

The Nobel assembly said that it is still unclear what the medical and scientific implications of the discoveries will be, but that the work could affect areas as diverse as psychology — to explain why scents often remind us of childhood — and cooking, since scent and taste are intertwined.

The award for medicine opens a week of Nobel Prizes that culminates Oct. 11 with the economics prize. The peace prize, the only one bestowed in Norway, will be announced Oct. 8. The physics award will be announced Tuesday and the chemistry prize will be announced Wednesday in the Swedish capital.

A date for the Nobel Prize in literature has not yet been set by the Swedish Academy, but is likely to fall on Thursday, Nobel watchers said.