[ExI] Research supports the Rare Earth theory

[John Clark]

On Mon, Feb 16, 2026 at 4:37 PM BillK via extropy-chat <
extropy-chat at lists.extropy.org> wrote:

> > Very Few Planets Have the Right Chemistry for Life
> *https://www.universetoday.com/articles/very-few-planets-have-the-right-chemistry-for-life
> <https://www.universetoday.com/articles/very-few-planets-have-the-right-chemistry-for-life>>*
> *Quote:*
> *The idea that life is inevitable elsewhere based purely on the staggering
> number of planets in the Universe is being chipped away at. Ultimately,
> we're in no position to make any solid judgements. But this research
> suggests that planets like Earth, where a million different factors lined
> up just right, are most likely exceedingly rare. *
>
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> * Unless some very different forms of "life" are possible.*


*The article is about the availability of nitrogen and phosphorus in a
planet's crust, and nitrogen is the 6th most common element in the
universe, and phosphorus is the 18th; and helium (#2), and neon (#5) and
argon (#11) are all chemically inert so they are no used to life.  **So if
extraterrestrial life uses elements other than nitrogen and phosphorus then
it must be even more "exceedingly rare". By the way, on Earth oxygen is the
most common element, even though cosmically it is only #3. *

*In many science fiction stories life is based on silicon (#8) chemistry
instead of carbon (#4) chemistry, but there are problems with that. When
carbon-based animals burn food for energy they produce carbon dioxide which
is a gas and is easy to expel, but the equivalent of that is silicon
dioxide (a.k.a. sand) so it would have to breed out solid crystals which
would greatly complicate respiration. Also, carbon can easily form double
and even triple bonds, and those are essential informing large complex
molecules that are needed to produce effective enzymes; but it's far harder
to form double bonds in silicon that are stable. And most silicon compounds
react strongly with water and break down into simpler molecules, you could
use liquid nitrogen as a solvent but at such a cold temperature the
reaction rate would be very slow.  *

*So silicon is great at electronics but not so good at chemistry.     *

*  John K Clark*


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