Carl Sagan, a titan of scientific study and communication, died in 1996, leaving behind an expansive legacy of research and education. He assumed a diverse set of roles throughout his life, including as a longtime casual user of and advocate for marijuana.

Sagan's involvement with pot began as a secret, when he penned an essay in 1969, at the age of 35, under the pseudonym "Mr. X." The piece, in which Sagan described the benefits he felt from using marijuana, later appeared in Dr. Lester Grinspoon's 1971 book, "Marihuana Reconsidered." Sagan's identity as the author wasn't publicly disclosed until 1999, when Keay Davidson published "Carl Sagan: A Life," which documented Sagan's writings as his alter-ego, "Mr. X."

Writing that he'd begun smoking intermittently around 10 years before, Sagan noted that marijuana "amplifies torpid sensibilities and produces what to me are even more interesting effects."

"The cannabis experience has greatly improved my appreciation for art, a subject which I had never much appreciated before," he wrote. "The understanding of the intent of the artist which I can achieve when high sometimes carries over to when I’m down. This is one of many human frontiers which cannabis has helped me traverse."

Sagan went on to explain in intricate detail how his experiences listening to music, eating food and even having sex were all heightened while high.

His essay also included some classic Saganesque poetry:

I can remember one occasion, taking a shower with my wife while high, in which I had an idea on the origins and invalidities of racism in terms of gaussian distribution curves. It was a point obvious in a way, but rarely talked about. I drew the curves in soap on the shower wall, and went to write the idea down. One idea led to another, and at the end of about an hour of extremely hard work I found I had written eleven short essays on a wide range of social, political, philosophical, and human biological topics. Because of problems of space, I can’t go into the details of these essays, but from all external signs, such as public reactions and expert commentary, they seem to contain valid insights. I have used them in university commencement addresses, public lectures, and in my books.

Sagan ultimately concluded that it was easy to use marijuana in moderation. For that reason he wrote that "the illegality of cannabis is outrageous, an impediment to full utilization of a drug which helps produce the serenity and insight, sensitivity and fellowship so desperately needed in this increasingly mad and dangerous world."

Years later, Sagan became more outspoken about his advocacy, arguing that medical marijuana should be legal for cancer and AIDS patients.

"Is it rational to forbid patients who are dying from taking marijuana as a palliative to permit them to gain body weight and to get some food down," Sagan asked in an interview. "It seems madness to say, 'We're worried that they're going to become addicted to marijuana' -- there's no evidence whatever that it's an addictive drug, but even if it were, these people are dying, what are we saving them from?"

Listen to his entire interview below: