Some scientific debates take a long time to resolve. Consider ALH84001. 25 years ago today, NASA announced that the meteorite from Mars contained evidence of ancient microscopic life. The news even brought a comment from President Bill Clinton.

CLINTON: Today, rock 84001 speaks to us across all those billions of years and millions of miles. It speaks of the possibility of life. If this discovery is confirmed, it will surely be one of the most stunning insights into our universe that science has ever uncovered.

Yet there was no confirmation from other scientists. Instead, there was near-universal disagreement.

NASA scientists had spent years examining the meteorite. They found shapes that looked like the fossils of microscopic organisms. They found minerals that formed four billion years ago, when Mars was warm and wet. They found organic compounds — the building blocks of life. And they found tiny magnetic crystals like those produced by life on Earth.

But other scientists disagreed with the conclusion. Their work showed that the possible fossils were too small, the chemistry wasn’t right, and the crystals could have formed when a shockwave rippled through the rock.

Yet the scientists who did the original work still say the rock shows evidence of life. A few other studies say that life is unlikely, but it can’t be ruled out. So the debate about life in this meteorite from Mars continues.
 

Script by Damond Benningfield