Despite being rather adamant about wanting evidence for everything, I've always had a hunch that the universe is inhabited, probably rather thickly. I am aware that it's just a hunch, however. I'm not translating a gut feeling into anything like certainty. But given what I know about the conditions necessary for generating organic molecules, and the power of natural selection even on the molecular level, I'd be mighty surprised if Earth turned out to be the only inhabited planet.
It does, however, demand a question -- one I remember my son asking a while back. Why is there any necessity that life (however we define that term, and it's far harder to define comprehensively than you'd think) has the same chemistry that it does here on comfortable old Earth? I still remember the first time I ran into that idea, back on the old Star Trek -- if you're my age, you probably remember the famous episode "Devil in the Dark," in which the intrepid crew of the Enterprise ran into the Horta, a creature whose biochemistry was based upon silicon instead of carbon. This is not as outlandish as it might seem. Silicon, like carbon, has four valence electrons, allowing it to form sheets, chains, rings, and other complex molecules rather readily. Most silicates don't dissolve much in water, which would require that any silicon-based life form have a different carrier in its vascular system; in the case of the Horta, it was hydrofluoric acid (which doubled nicely as a defensive weapon in dissolving any unfortunate red-shirted security officers it happened to run into).
My point here, and I'm hardly the first to make it, is that a life form with a dramatically different biochemistry might well be hard to recognize as life. In our search for extrasolar planets, we tend to get most excited about the earthlike ones, because of a sense that those are the only ones that could harbor life. But is this necessarily true?
The whole topic comes up because of a recent statement, by Russian astronomer Leonid Ksanformaliti, that he has discovered evidence of life on Venus. Now, Venus was one of the first solar planets that was ruled out as possible site for life when it was discovered exactly how inhospitable is is. Clouds cover the surface, the discovery of which led many to speculate that it had liquid water, oceans, and possibly a breathable atmosphere (H. P. Lovecraft and C. S. Lewis both wrote stories about an inhabited Venus), but now it is known that the clouds are largely made up of sulfuric acid, and the surface temperature is a balmy 850 degrees Fahrenheit, with a barometric pressure 92 times higher than Earth's. The conditions are so hellish that the first probes dropped onto the surface fried before they returned much useful data back to scientists here at home.
So, Ksanformaliti, who made his claim in Russian journal Solar System Research, is making what appears to most scientists a pretty outlandish claim. Ksanformaliti and his team analyzed photographs from earlier missions, some dating back to 1982, and found what he calls "biological forms" -- he nicknames three of them "black flaps," "disks," and "scorpions." “What if we forget about the current theories about the non-existence of life on Venus?" Ksanformaliti told reporters for The Daily Caller. "Let’s boldly suggest that the objects’ morphological features would allow us to say that they are living.” (See a photo of one of them here. Don't get your hopes up about the video clip, however -- it's just a gradual zoom-in on the object in the still, along with hyperdramatic music.)
Of course, this makes most of us raise our eyebrows. Organic compounds as we know them fall apart when subjected to conditions like those on Venus, so life should be impossible there. But we are, of course, basing that judgment on the life we know. Is it possible that even considering the high-pressure inferno that is Venus, that something may be down there that qualifies as life?
Possibly -- but I need more than a bunch of fuzzy photographs before I'm ready to join Team Leonid. As I've had reason to comment before, humans are just too prone to attribute lifelike qualities to non-living objects to trust that we would recognize life here on such flimsy evidence. And, for the record, I still think our best bet for life in our own solar system is one of the larger moons of either Jupiter or Saturn.
But I will maintain that regardless, if Ksanformaliti makes us reconsider our assumptions about life, that's all to the good. If SETI and other projects like it have a prayer of a chance, it will only come from thinking outside the box -- and from being willing to redefine what we mean by the words "life," "organism," and "intelligent."