Where Martians Come From
I learnt something disconcerting today, about astronomer Percival Lowell (1855-1916). Lowell is famous for observing and describing channels or “canals” on the surface of Mars. Lowell speculated that these canals were non-natural structures built by intelligent beings to carry water from the polar ice caps to martian cities, where water was scarce. This theory was highly popular among the public, nurturing the fantasy that there was life on Mars.
The scientific community, however, remained skeptical as no one was able to come to the same observations. There is indeed a giant canyon (Valles Marineris) on Mars—a sign that there was once water flowing on the surface—but nothing like the complex structures Lowell was describing. Here is a drawing he made of his observations:

Lowell also turned his telescope to Venus, and there too observed canals. Lowell maintained that Venus displayed a network of massive canals emanating from a central hub or black spot:

The most troubling aspect of this discovery was that the canals and the black spot seemed constantly pointed at Earth. They were not rotating with the planet, but rather floating above it, like a device meant to keep an eye on us. A weapon maybe?
Could there be intelligent, hostile beings on Mars and Venus?
Once again, no other astronomer was able to reproduce the observations, yet no one truly questioned Lowell’s work at the time, because his mountaintop observatory was one of the most advanced in the world. It is from this observatory that Pluto was later discovered, in 1930.
Lowell’s mystery canals remained a mystery for a century, until an explanation was proposed, in 2002, by Minnesotan optometrist Sherman Schultz.
Schultz examined the optical setup of Lowell’s telescope and noted that it was similar to the one he used to examine patients’ eyes. He suggested that what Lowell had seen, on Venus and Mars, was actually the shadow cast on his own retina by the blood vessels in his eye. This hypothesis was rapidly confirmed, comparing Lowell’s drawings to photographs of blood vessels in the retina.
Ouch.
Science fiction is in the eye of the beholder:

Sources:
Death by Black Hole, by Neil DeGrasse Tyson
Wikipedia
Sky & Telescope Magazine
