[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

On making Earth-like planets

I have just finished reading a fascinating article
in the Meteoritic and Planetary Sciences Journal that
just arrived.

It is by Stuart Ross Taylor who wrote The Evolution of the Solar System -
a New Perspective.

Taylor was involved with the Lunar recovery mission at NASA and has a broad
background in geology, astrophysics, and chemistry. A rare mixture
of talents needed to synthesize the results from our exploration 
of the solar system these last few decades.

He argues that the origin of planetary systems is largely chaotic.
We have observed a small number of other planetary systems recently via Hubble -
each is unique.

All planetary systems must have evolved from molecular clouds
emitted from supernovae events, because the early universe had
only hydrogen and helium - all other matter resulted from nucleosynthesis
in mature stars.

When the molecular clouds settle into star systems, the initial angular
momentum and distribution of matter dictates whether there will result
a single star or multiple star system - most stars form multiple star systems.

Probable only single star systems can evolve planets with potential for life.

Even in the infrequent single star systems that evolved from the first generation
stars, most will evolve a Jupiter-like object at the ice point in that solar system.

This early planet will dominate the evolution of the rest of the planetary system.

If the star that is forming in that cloud has ignited coincident with the formation of
the Jupiter object, it will sweep out dust and gas in the inner planets formation area;
if not, the Jupiter object will be exposed to the dust and slow down - winding into an
orbit close to the new star and obliterate any possible earth-like planet.

Taylor goes on to discuss that the habitable range in a star system is very narrow,
and the likelihood of a planet format at that region only a matter of chance.

Many more details are presented; his conclusion being that even with 500 billion galaxies
of 100 billions of stars each - the chance are still minute that another earth-like
planet will have been made.

Even those that do happen, they still endure the planetary bombardments that must be common
on solar systems - events that obliterate planetary atmospheres or severely impact the development
of life every few millions years - giving advanced life a very narrow window of time to evolve
before a major disaster occurs.

When the requirements that plate tectonics to provide heavy minerals for technology are added,
along with a large satellite to provide tides for life to evolve, it seems to me his arguments
are very persuasive.

Carl Sagan would undoubtedly object to much of this if he were alive, but I find Taylor's argument
to be very moderate, level-headed, and sobering.


--
Jim Hurley  Freelance graphics artist
Web page design; graphics; multimedia
  <URL: http://www.arachnaut.org/ >

----------
Archives located at:
http://www.meteoritecentral.com/list_best.html

For help, FAQ's and sub. info. visit:
http://www.meteoritecentral.com/mailing_list.html
----------