Percival Lowell died in 1916, unaware that his photographic plates had captured Pluto.
This photographic plate was among the ones Clyde Tombaugh used to discover Pluto. On Jan. 29, 1930, a point of light that had previously appeared on the left of two bright stars now showed up on the right. Only planets make such moves.
The Jan. 23, 1930, plate showing Pluto on the left of two bright stars. Lowell Observatory
Lowell at his telescope.
In the closing decade of the 19th century, Percival Lowell was a romantic soul searching for a proper career. His intellectual wanderings would lead America to Martian mania and launch the scientific search that would uncover Pluto.
Lowell came from a prominent Boston family. His brother was a long-standing Harvard president, his cousin edited the Atlantic Monthly, and his sister did what young, educated women of the time did -- smoked cigars and wrote poetry.
Lowell, who trained as a mathematician at Harvard, had already spent several years in Japan by the 1890s; he was looking for a civilization more expansive, more evolved than what he had known in Boston, says David Strauss, professor emeritus of history at Kalamazoo College and author of Percival Lowell: The Culture and Science of a Boston Brahmin.
Lowell, however, concluded that Japan wasn't high on the civilization ladder. Their language and culture, he said, showed the Japanese had a lack of personality.
He headed back to the States and, frustrated with life on Earth, turned his search for a superior civilization toward space. A series of maps by the Italian astronomer Giovanni Schiaparelli had piqued his interest.
They showed a series of "canalis" -- Italian for channels -- criss-crossing the planet in a fashion that, to Lowell, seemed too orderly to have happened by geologic chance. Using his well-managed family money, Lowell set up an observatory in Flagstaff, Ariz., to investigate.
When the skies were clear, he sat at his observing chair, looking through his telescope for glimpses of Martian civilization. He made hundreds of sketches and concluded that Mars was a dying a planet.
The planet was drying out, Lowell's theory went, and the beings there had developed an extensive irrigation system to draw waters from the polar ice caps.
"Lowell was able to spin a yarn from observations of linear detail on Mars into this wonderful story of a planet gripped in climate change, rapidly becoming a desert, and a wise people who were able to put aside party politics and come up with an organized plan to save themselves," says Bill Sheehan, historian and author of Mars: The Lure of the Red Planet.
Through Lowell's theories, life on Mars became a "national obsession," Sheehan says.
His Mars books became bestsellers, and newspapers such as the New York Times and Wall Street Journal touted his theories and images of the planet.
"The idea of intelligent life on Mars sounds kooky until you read his books," says David Strauss. "When you read those books, you're impressed by the logic of his argument."
Unless you were a professional astronomer. Lowell had no real proof for life on Mars, and he was roundly criticized for views other astronomers considered sensational.
But Lowell wanted professional acceptance, says Sheehan, so he turned to a mathematically exacting project that could redeem him in the eyes of his peers: the search for a ninth planet. Lowell called it "Planet X."
What's Tugging on Neptune?
Neptune had been discovered in 1846 through mathematical calculations, based on its gravitational pull on Uranus, that predicted the planet's orbit. With the orbit in hand, astronomers knew where to look in the night sky.
Lowell used the same idea for Planet X. Based on irregularities in Neptune's orbit, supposedly caused by Planet X, he and his hired team of Harvard mathematicians calculated Planet X's mass and orbit.
A second team took photographic plates of the sky where Planet X was expected to be.
After 13 years of searching, Planet X remained hidden. Lowell died in 1916, depressed and frustrated, says Strauss. "He said the great disappointment of his life was the failure to find Planet X, and he was living with that clearly at the moment he died."
But the search for Planet X continued at Lowell Observatory, buoyed by a grant from his brother, Harvard president Abbott Lawrence Lowell.
In 1930, Clyde Tombaugh -- hired by the observatory to examine hundreds of new photographic plates -- compared a pair and noticed that a tiny spot of light had changed locations from one plate to the other. Faraway stars remain in fixed locations in the plates, but planets move. Tombaugh had found what was later named Pluto, traveling in its orbit.
Pluto had a different orbit and was far smaller than Lowell had calculated, but it was the ninth planet. And in fact, when astronomers went back and searched, they found Pluto in several of Lowell's photographs, so faint, it looked like one of the thousands of stars in the images.
"He's sort of a double-edged sword," says David Catling, professor of astrobiology at the University of Bristol. Planetary science's reputation took a blow when Mars turned out to be uninhabitable.
But Lowell advanced the field in general by encouraging the exploration of planets and the discovery of Pluto, Catling says. "That's his lasting legacy."