groups

LenRobertson says,
. . . At the same time, evidence of liquid water on an exoplanet becomes proof enough that it's a living planet.

Just because there's water don't mean there's life. I put lots of naturally occurring chemicals in my swimming pool to make sure that don't happen. A planet that has too much chlorine, Bicarbonate soda, and other chemicals that upset the PH balance of water, and nothing grows. Life is a chemical process. Without the right chemicals, in the right amounts and the right order, you don't have life.

The argument that Earth is the fountainhead of all life in the Cosmos joins Creationism and Lightning and Amino Acid Darwinism in the dustbin of idiotic ideas. posted by LenRobertson

Yep it's kind of like proclaiming that "evidence of liquid water on an exoplanet becomes proof enough that it's a living planet." Proof enough for who?

Everyone is assuming that "All Life" is carbon based. I wouldn't be surprised if there is life out there that is not carbon based!

Monteguy says,
Everyone is assuming that "All Life" is carbon based. I wouldn't be surprised if there is life out there that is not carbon based!

Well, there's a reason for that. . . . The basic building block for everything from stars to a grain of sand is carbon. So, since everything in the universe is carbon based, it only stands to reason that everything in the universe is carbon based.

I thought that the Basic Building Block was Helium, which subsequently creates carbon!

According to my wife, the slime queen (12 patents, 48 published articles, 3 chapters in graduate texts), "It doesn't matter what one uses, one never kills them all." Sooner or later, one needs something else to defeat the blooms. The rule is true whether it's a paper mill or someone's backyard swimming pool.

What does that have to do with life across the Cosmos? It means that organic life sooner or later makes itself at home as long as there is one compound in liquid form: water. There are organisms that thrive in boiling water, beneath glaciers and under intense radiation. There are organisms called extremophiles that have resistance against a long list of threats.

And, then there is Deinoccucus Radiodurans, called by NASA Conan the Bacterium. It is resistant to heat, cold, dryness, exposure to deep space and radiation. In fact, when it comes to radiation it puts robots to shame. Humans can stand 140 roentgens in their lifetime. Cockroaches can stand 6 times as much. Conan? How about 1,500,000 roentgens.

Is Conan the toughest critter in the Cosmos? Don't know, but probably not. In fact, as we learn about life elsewhere, we may find it is a 97 lb weakling.

Who said the 21st Century will be dull?

One more point (and probably the most important). Recent evidence such as evidence of micobes 500 million years (not long after Earth cooled) points to life originating elsewhere in the Cosmos. It is one thing for life to be some king of fortunate accident that rarely happens. It's quite another if the sources of life are asteroids and meteorites laden with poly extremophiles spreading across the Cosmos for billions of years. One makes for very few living planets: the other guarantees that life exists everywhere (maybe even Luna for a time).

Hydrogen is the most abundant element in the universe, by mass, followed by helium, oxygen, then carbon. Nitrogen, phosphorus, arsenic, chlorine and sulfur are candidates for hypothetical non carbon based life due to thier abilities to form long chain molecules. Ammonia and hydrogen fluoride are potential substitutes for water as a solvent to life.

Fungi have the ability to convert gamma rays to energy using melanin... In other words it's quite plausible life elswhere in the cosmos thrives without photosynthesis and exists without carbon based organic molecules.

You're mostly correct. Still, if you ask any microbiologist if a planet like Gliese 581d has life, they will ask one question, "does it have water?"

"Yes. The whole planet is water."

"Then, it has organic life."

As you note, oxygen is not a prerequisite. In fact, the first organic life that existed 500 million years after Earth was formed seems to have been anaerobic.

Restating Martinus Beijerinck's "Everything is everywhere," the question has to be whether all life always begins at 0 whether life began at 0 once long ago and far far away and it has been drifting across the Cosmos since that time. If the second alternative is the more correct, it's safe to theorize that carbon based life fills available nitches before anything else has a chance.

Interestingly, carbon based life aboard asteroids and meteorites makes it possible for a planet to have false starts (as apparently happened on this planet) before organic life finally establishes itself permanently. In other words, life this planet has suffered some mighty blows (most notably the Permian-Triassic extinction), but it was never in danger of total extinction. Not if, as Beijerinck says, "everything is everywhere".

If "everything is everywhere" and convergence rather than divergence in evolution is dominant, we may find others aren't all that different from us. That is the approach I take in my sci fi.

Monteguy says,
I thought that the Basic Building Block was Helium, which subsequently creates carbon!

Well, that's what you get for "thoughtin'"
Here's the real scoop on the make up of organic compounds. (aka life)

The simplest organic compounds contain molecules composed of carbon and hydrogen. The compound methane contains one carbon bonded to four hydrogens. ...
www.edinformatics.com/math_science/ c_molecule.htm

Learn why carbon is is the building block to molecules of life.
www.nyu.edu/pages/mathmol/modules/ carbon/carbon1.html

Now ya can't say ya didn't learn something today. LOL