RE: Earths difficult?

From: Amara Graps (amara@amara.com)
Date: Thu Jan 30 2003 - 02:14:17 MST


No, I haven't read it, but I suggest starting here for this this author's
work on this topic. Generally, I do not trust anything written by BBC's
science writer: David Whitehouse.

Amara

http://xxx.lanl.gov/abs/astro-ph/0210006

Astrophysics, abstract
astro-ph/0210006

From: Kristen Menou <km5yj@astsun.astro.virginia.edu>
Date: Mon, 30 Sep 2002 20:56:05 GMT (115kb)

Dynamical Habitability of Known Extrasolar Planetary Systems

Authors: Kristen Menou, Serge Tabachnik
Comments: 38 pages, 7 tables, 7 figures, accepted for publication in ApJ

      Habitability is usually defined as the requirement for a
      terrestrial planet's atmosphere to sustain liquid water. This
      definition can be complemented by the dynamical requirement that
      other planets in the system do not gravitationally perturb
      terrestrial planets outside of their habitable zone, the orbital
      region allowing the existence of liquid water. We quantify the
      dynamical habitability of 85 known extrasolar planetary systems
      via simulations of their orbital dynamics in the presence of
      potentially habitable terrestrial planets. When requiring that
      habitable planets remain strictly within their habitable zone at
      all time, the perturbing influence of giant planets extends beyond
      the traditional Hill sphere for close encounters: terrestrial
      planet excursions outside of the habitable zone are also caused by
      secular eccentricity variations and, in some cases, strong
      mean-motion resonances. Our results indicate that more than half
      the known extrasolar planetary systems (mostly those with distant,
      eccentric giant planets) are unlikely to harbor habitable
      terrestrial planets. About 1/4 of the systems (mostly those with
      close-in giant planets), including 1/3 of the potential targets
      for the Terrestrial Planet Finder, appear as dynamically habitable
      as our own Solar System. The influence of yet undetected giant
      planets in these systems could compromise their dynamical
      habitability. Some habitable terrestrial planets in our
      simulations have substantial eccentricities (e > 0.1) which may
      lead to large seasonal climate variations and thus affect their
      habitability.

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-- 
Amara Graps, PhD
Istituto di Fisica delle Spazio Interplanetario (IFSI)
Consiglio Nazionale delle Ricerche (CNR), Roma, ITALIA
Amara.Graps@ifsi.rm.cnr.it


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