Re: alternative to terraforming

From: Amara Graps (
Date: Sun Jun 04 2000 - 06:45:38 MDT

From: Anders Sandberg <>, Date: 03 Jun 2000

>One problem is that asteroids seem to be more like piles of rubble
>than solid blocks, they might not survive being spun up. One
>possibility is to cover them with a mesh to keep everything in place
>and excavate anyway, or adapt to life in microgravity.

No, this is too sweeping of a statement. *Some* asteroids are like
rubble piles, but no one knows the percentage of asteroids that are
like that. In fact, the existence of fast asteroid-rotators shows
that some asteroids are _not_ rubble piles. The range of asteroid
rotation goes from periods of a few hours to about a thousand hours,
and the asteroid 1998 KY26 has the shortest asteroid rotation period
in the solar system: 10.6 minutes. Big and little asteroids have
different distributions of rotation periods, and Kuiper belt objects
are yet another class, formed differently, with different rotation

Here are some astracts that might be useful.


 Title: Alteration of Asteroid Spin States During Close
                     Planetary Encounters
 Authors: Scheeres,D.J.; Ostro,S.J.; Asphaug,E.I.;
 Affiliation: AA(Univ. of Michigan), AB(JPL/Caltech),
                     AC(UC-Santa Cruz), AD(Wash. State Univ.)
 Journal: American Astronomical Society,
                     DPS meeting #31, #24.08
 Publication Date: 09/1999
 Origin: AAS
 Abstract Copyright: (c) 1999: American Astronomical Society
 Bibliographic Code: 1999DPS....31.2408S


Rubble-pile asteroids can have their shapes and spin states altered,
perhaps dramatically, by close planetary encounters (Bottke et al.
1998, Planet. Space. Sci. 46,311; 1999, Astron. J. 117,1921).
However, despite their popularity, the relative abundances of
rubble-pile and monolithic asteroids as a function of size are
unknown. At least one tiny asteroid, 1998 KY26, certainly is
monolithic (Ostro et al. 1999, Science 285, 557), and the harsh
angularity of 6489 Golevka ( Hudson and Ostro 1995, BAAS 27, 1062)
and prominent linear ridges on 4179 Toutatis (Hudson and Ostro 1995,
Science 270, 84) may suggest monolithic interiors.

We present an initial exploration of the effects of close planetary
encounters on the spin states of monolithic asteroids using both
analytical and numerical techniques. Our analysis can be applied to
an arbitrary flyby geometry between a planet and an asteroid of any
shape and initial spin state. We have used the theory to guide
numerical integrations of Toutatis' interaction with the Earth
during a close flyby. Our results indicate that such flybys may have
placed an initially uniformly rotating Toutatis into its current
rotational state. Application of the analysis over a wider parameter
space may indicate the degree to which close encounters share
responsibility for current near-earth asteroid spins.

 Title: Bayesian statistical analysis of asteroid rotation
 Authors: Donnison,J.R.; Wiper,M.P.
 Affiliation: AA(Department of Mathematical and Computing Sciences,
                     Goldsmiths College, University of London, New Cross,
                     London SE14 6NW ), AB(Departamento de Estadistica y
                     Econometria, Universidad Carlos III de Madrid, Madrid,
                     Spain )
 Journal: Monthly Notices of the Royal Astronomical Society,
                     Volume 302, Issue 1, pp. 75-80. (MNRAS Homepage)
 Publication Date: 01/1999
 Origin: MNRAS
 Abstract Copyright: (c) 1999 The Royal Astronomical Society
 Bibliographic Code: 1999MNRAS.302...75D


Asteroid rotation rates have been analysed by many authors in the
past, and one or more Maxwellian distributions have been fitted for
various diameter ranges and taxonomic classes. The statistical
results and physical interpretations of the models have varied
widely. In this new approach we use Bayesian statistics to determine
the separation of the larger asteroids, which are fitted with a
single Maxwellian distribution, from the smaller asteroids, which
are fitted by a mixture of Maxwellian distributions. It is found
that the optimal separation occurs at about 32.5 km, and that a
mixture of three Maxwellians comprising slow rotators, fast rotators
and a population identical to the larger asteroids provides the best

Amara Graps email:
Computational Physics vita: finger
Multiplex Answers URL:
"It works better if you plug it in." -- Sattinger's Law

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