In 1971, Apollo 14 astronaut Stuart Roosa carried hundreds of tree seeds around the Moon in a metal canister inside his personal kit. When the seeds returned to Earth, many were germinated by the U.S. Forest Service and planted as “Moon Trees” — ordinary-looking trees that, decades later, showed no discernible difference from trees whose seeds had never left Earth.

In 1971, Apollo 14 astronaut Stuart Roosa carried hundreds of tree seeds around the Moon in a metal canister inside his personal kit. When the seeds returned to Earth, many were germinated by the U.S. Forest Service and planted as “Moon Trees” — ordinary-looking trees that, decades later, showed no discernible difference from trees whose seeds had never left Earth.

The story sounds like it should end with a twist. An astronaut carries tree seeds around the Moon, the seeds are planted back on Earth, and the trees that grow are, in every way anyone has measured, just trees. That is more or less what happened. In 1971, Apollo 14 command module pilot Stuart Roosa took a canister of seeds with him into lunar orbit. The seeds came home, the United States Forest Service coaxed many of them into seedlings, and tho…