We are now just past an excellent close approach, called by astronomers an “opposition,” of the planet Mars. Mars will not be as bright in the sky or as big in a telescope until 2035.

Oppositions of Mars sometimes brings out the “crazy” in astronerds, especially on the subject of extraterrestrial life. Occasionally, even professional astronomers have advanced theories about the two objects that in retrospect sound pretty bizarre.

Such was the case in 1895, when, night after clear night, Percival Lowell trained his enormous refracting telescope in Flagstaff, Arizona, at mysterious Mars.

He saw the small Martian polar caps, which he concluded were composed of life-giving water. He, along with other astronomers, saw mysterious green splotches on its surface. He noticed that the green markings got bigger in the Martian summer and smaller in the Martian winter.

Most significantly, he saw thin lines crisscrossing the planet. He concluded that the lines were canals designed and built by a race of intelligent Martians to transport the water from the Martian polar caps to the rest of Mars extraordinarily arid surface.

That water supported the green splotches, which he imagined were enormous fields of vegetation.

You’d think that such conclusive evidence for life on another planet would produce quite a stir, and it did, but not so much as you might expect.

Here’s how many astronomers responded: Big deal. Of course life exists on Mars. It exists everywhere in the universe. We will probably never interact with the intelligence that created the canals. The great gulf between the two planets made that unlikely. The civilization on Mars might as well have been at the other end of the universe for all the good it did us.

As we now know, Lowell was totally wrong. The polar caps are made up mostly of frozen carbon dioxide, also known as dry ice.

The green markings aren’t really green. They look green because of their juxtaposition with the orange-red of the Martian soil. Lowell was tricked by an optical illusion.

They are actually gray, as one might expect from exposed rocks, which they indeed are. During the Martian summer, Mars often experiences gale force winds, which blow the Martian soil off its rocky features. The green markings get larger.

During the Martian winter, the gentler winds blow the Martian soil back up onto the rocks. The green markings get smaller.

Nobody knows for sure what trick of the eye caused Lowell to see canals. But as many visiting spacecraft from Earth have verified, the danged things simply aren’t there.

Lowell’s canals were small potatoes compared with the later Martian meanderings of Russian astrophysicist Iosif Shklovsky. In 1959, Shklovsky concluded that Phobos, one of the two small moons of Mars, must be very low in density. How could it weigh so little and still be rigid enough to hold together?

According to Shklovsky, Phobos must be an artificial satellite created by an advanced civilization on Mars some hundreds of millions of years ago. Twenty years later, well after the astronomical community’s ridicule had died down, a thoroughly chastened Shklovsky wrote that the whole thing had been a practical joke.

Shklovsky has faded into astro-history. However, much of our modern Martian mythology is still based on Lowell’s mistaken observations.

Subsequent science fiction writers had a field day. They envisioned giant underground cities inhabited by advanced Martian civilizations.

The tall, skinny “bug-eyed monsters” (BEMs, for short) that inhabit the American imagination to this day are direct products of the supposed evolutionary effects of the Martian environment. BEMs should be tall and slim, because Mars is small and doesn’t have much gravity and atmospheric pressure to pull them down to short and stocky.

Mars is farther from the sun and doesn’t get as much light as Earth. BEMs need those big eyes to see well.

The most influential science fiction version of Martians was probably the H.G. Wells novel “War of the Worlds,” which was first published in 1897. The Martian invasion of Earth depicted Martians as world conquerors.

The Martians were equipped with enormous, terrifying three-legged “fighting-machines.” They had armed each machine with a heat-ray and a poisonous chemical weapon, the deadly “black smoke.”

Their invasion left our planet devastated, and there was nothing that humans could do to stop their destruction. In the end, the Martians were defeated not by our weapons of war, but by Earthly microbes for which they had developed no immunities.

“War of the Worlds” is still in publication to this day. It has spawned half-a-dozen movies, and most notably, one infamous radio play.

On Sunday, Oct. 30, 1938, the nationwide Columbia Broadcasting System radio network broadcast Orson Welles’ version of the H.G. Wells novel. Wells’ experienced troupe of players performed it live as the Halloween episode of “Mercury Theatre on the Air.”

If people listened to the show from the beginning, they realized that it was a fictional radio play set in 1939, the year after the contemporary date.

If they missed the introduction, they were stunned by a live music program interrupted by news bulletins. Slowly, Carl Phillips, the on-scene reporter, revealed the Martian invasion and the resulting destruction.

Set near New York, the play caused widespread panic. Police stormed the building and demanded that the broadcast be halted.

The terror that some people, ignorant of the fictional nature of the program, felt is understandable. The first-person narration by the reporter is vivid, especially in its horrifying description of the Martians. Here’s an excerpt from the script:

“Ladies and gentlemen, this is the most terrifying thing I have ever witnessed! Wait a minute! Someone’s crawling out of the hollow top. Someone or … something. I can see peering out of that black hole two luminous disks.”

“Are they eyes? It might be a face. It might be … (shout of awe from the crowd) Good heavens! Something’s wriggling out of the shadow like a gray snake. Now it’s another one, another and another. They look like tentacles to me.”

“There, I can see the thing’s body. Now it’s large, large as a bear, and it glistens like wet leather. But that face, it … ladies and gentlemen, it’s indescribable, I can hardly force myself to keep looking at it.

“Oh, the … eyes are black and gleam like a serpent. The mouth is … is kinda v-shaped, with saliva dripping from its rimless lips that seem to quiver and pulsate.”

As police began to fill the broadcast building near the end of the first hour of the show, the producers of the program hurriedly announced the fictional nature of the show yet again.

But it was too late to stem the tide of panic. By the time of the announcement, the main character was choking on the poisonous black gas in the city, and many terrified people had abandoned the program.

Some of them had run into the streets to spread the word. Others called radio stations and newspapers asking for verification of the invasion.

A few phoned in false reports of Martian sightings. Many called loved ones in New York to find out if they were affected. As the phone lines jammed, people could not get through to friends and loved ones. They often assumed the worst, and further panic ensued.

Although the panic was probably exaggerated afterward by sensational news coverage, the long-lasting effects of the broadcast clearly demonstrated the power of the myth of Martian life.

That myth continues to this day. I’ll give you a small taste of it next week.