Better late than never to celebrate Carl Sagan Day, dedicated to the best flirt I ever encountered. The man was a world class flirt! Popular Science featured an interview from September, 1972, which was a good ten years before he became such a hot property.
“…Fisher: What kind of picture of atmospheric conditions on Mars do we get from this analysis?
Sagan: That Mars is a dusty and very windy place, even though the atmosphere is quite thin; temperatures near the equator at noon are very comfortable by human standards, but the temperature at night or very early in the morning is extremely low, maybe 150 Fahrenheit degrees less than room temperature. There’s little oxygen in the atmosphere. There is very little ozone, so ultraviolet light from the sun is not absorbed as it is in our atmosphere and penetrates to the surface relatively unimpeded, if there’s no dust storm. This would pose a serious hazard for exposed organisms of a terrestrial variety.
Putting all those factors together, people in the past said the Martian environment was probably too severe for life. In my view that’s an exceedingly provincial conclusion. We, and others, have done experiments in which we simulate all these conditions in the laboratory. We found that even a wide variety of terrestrial organisms survive those conditions perfectly well. They survive the ultraviolet light when they’re under a tiny fragment of rock, and they even grow during the warm part of the day if there are small quantities of liquid water available in the soil, which is by no means out of the question on Mars today.
Fisher: What kinds of organisms are you talking about?
Sagan: I’m talking about microorganisms: bacteria—spore forming, or non-sporeforming bacteria.
Fisher: But nothing like lichens?
Sagan: Well, lichens are the kind of standby in the speculation about life on Mars because they are supposed to be hardy and all, but they’re not at all hardy under Martian conditions. If there is life on Mars, what’s clear is that—unless we’ve contaminated the planet by not sterilizing our spacecraft—life we find is going to be extremely different from life on the Earth. At least that’s my own belief. Life on Mars will have gone through 4½-billion years of independent biological evolution. There are so many arbitrary branch points in evolution…
Fisher: …that is, 4½-billion years ago…
Sagan: Yes, 4½-billion years ago. Well, life certainly is not arising now. The conditions on Mars today are much too perilous for the origin of life. That requires very protected conditions. But they are not too perilous for the maintenance of life. The origin of life on Mars, just like the origin of life on Earth, must have occurred a great interval of time ago in the past. I mean the origin of life on Earth could not have happened on the Earth, either, if conditions were like today’s—much too hostile. For example, we have an enormous poisonous atmosphere of oxygen which would prevent the origin of life. Mars is in fact better in that respect by not having much of this poison gas. Oxygen oxidizes organic compounds. It’s not a good thing to have around. Because we humans breathe it we think it’s terrific. That’s also a provincial point of view.
The conclusion I’d like to make about life on Mars is that there is certainly no compelling evidence for it, but there is equally certainly no compelling evidence against it. Mariner 9 was not designed to detect it nor has it detected life on Mars. The Viking mission will be the first serious attempt to find life on the planet. At the present time the conditions on Mars are certainly not too hostile for life to exist. We must merely keep an open mind until more data is in….”