If the angle of descent were a bit steeper, I would make a WAG that it was his ratings. 
Probably any of the Solar System’s planets, (with the exception, perhaps, of Mercury and Pluto),** as well as several of the “moons” of other planets, could support “life”.**
If you mean, however, “…what planets…can support Earthly life…?”, then the answer is, as you said, “probably none except for Earth”.
Just because something doesn’t look like[ul][li] a human or []Flipper the Dolphin or []Willy the Orca or []Lassie the Dog or[] Tiny the T.Rex or[]Burp the Frog or[]Dorid the Sea Slug or[]Stony the rock or[]Briareus the Reef Octopus or[] {innumerable list of possibly “sentient” representatives of Earthly species} [/ul]doesn’t mean that[list=A][]it’s not “alive”; []it’s not “life”; or[]it’s not “sentient”, (to include “capable of exploring outside of it’s planet’s gravitational well”).[/list=A]Your view of what is “life” seems to be extraordinarily limited.[/li]
(Don’t like the “Stony” example? How “sentient” is your computer? A recent GD thread said that none other than a famous Cosmologist has just recently suggested that computers may develop a level of artificial intelligence sufficient to threaten mankind’s position as “chief-species” on Earth. Silicon. Germanium. Rock!)
Quite possibly, but there are limiting factors to reasonable conjectures on extraterrestrial life. Any lifeform has to be able to breathe, so we can rule out airless worlds, like Mercury and Pluto. A lifeform has to live in a stable range of temperatures, too hot and organic compounds can’t form; too cold and chemical processes shut down, so we can rule out the sun, Venus, and the gas giants. That’s not prejudice for Earth-like life; that’s just the facts. There may well be wild and exotic forms of life out in the starry void, but they still have to obey the laws of physics and biochemistry. As much as it is to fantasize about flame creatures living in the sun and intelligent balloons floating in the atmosphere of Jupiter, the facts as we know them say that the likelihood of life existing in our solar system is vanishingly small.
gobear wrote:
I agree that the “wild and exotic forms of life” have to obey the laws of physics but not the laws of biochemistry!
Silicon makes a good alternative to carbon; I don’t have a cite but I read the details many years ago. No one, of course, has the foggiest idea what a “silcon-based life form” might look like nor how they would construct themselves (–the alternative to our DNA). Nonetheless…
More: Certainly carbon compounds are one of the most well studied in human chemical science. What, if anything, wasn’t known about the simple carbon-based chemicals? They even have their own name: “Biochemicals”. How far back in antiquity were “buckyballs” (C[sub]60[/sub]) found? Who knows what’s next? And how many “nexts” (with respect to carbon compounds) there are in the future?
You can find good explanations of why silicon-based life isn’t very likely [http://www.uwinnipeg.ca/~vincent/Cosmology/silicon-based_life.htm"]here](
[url) and [here](http://www.sciam.com/askexpert/astronomy/astronomy28/astronomy28.html).
While silicon seems at first glance to be an ideal substitute for carbon (both have valences of four, both are stable and plentiful elements), there are problems with using silicon as a base for life. For one thing, when carbon (the element we are based on) combines with oxygen, it forms a gas, carbon dioxide. When silicon combines with oxygen, it forms a solid, silica. This presents enormous waste disposal difficulties. If silicon-based life doesn’t use oxygen, (say, a silicon-methane life form instead of a carbon-oxygen), it’s going to be a very slow-moving organism.
Another problem is that while carbon can form bonds with a great many elements creating stable compounds, silicon can’t. Despite years of research, scientists have not been able to form stable silicon versions of carbon compounds. so silicon lacks the ability to
There may be silicon-based life elsewhere, but it is bound to be mighty fragile and rare.
I admit, gobear, that while I was always very interested in biochemistry, I never made past Organic—too many names to memorize so, one day, I “jumped ship”, headed down the hallway to the math department and immigrated. Besides that, the Chemistry Department smelled bad. Worse, the Chemical Engineering Dept. was in the basement under Chem. and the stuff that came up the stairwell REALLY stank. The worst smells in math are chalk-dust. 
I particularly liked your link to London’s Sunday Times story Alien Life Forms May Be Inside Earth by Steve Farrar, Science Correspondent. But, of course, that Golden news-story favored Silicon-based lifeforms so it’s not surprising that I liked it.
We shall see, I reckon.
By the way, the REAL question about lifeforms seems to revolve around the bacterial/mitochondrial level of form. There has been a recent spate of bioscience stories about some pretty bizarre bacteria, here and there on Earth (in the icy wastes of subsurface Antarctic lakes; in the hotter-than-boiling gysers under the Pacific Ocean; etc.). The sedentary version of the nomadic bacteria are the guys who maintain single-cells. We haven’t found any multi-celled organisms “powered” by a sedentary version of one of these bizarre bacteria, but, at least in the deep-water case, we have great trouble getting them to the surface intact. In the Antarctic case, no one has even looked for organisms yet, so far as I know.
So: Who knows. Scientific knowledge progresses. 