**John McCarthy**

*Computer Science Department*

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Stanford University

In a chaotic dynamical system, small deviations from given initial
conditions produces large changes over time. This suggests that
chaotic systems are controllable by making small changes initially.
The solar system is a somewhat chaotic dynamical system, so maybe
humanity can control its evolution to produce desired effects.

The specific idea of this article is to move the planet Mars to an orbit at the same distance from the sun as the earth's orbit. This would make Mars warmer, which might make it more habitable.

The scheme is to use a *tame asteroid* that makes several
thousand encounters with Mars, Venus and Jupiter to exchange energy
and angular momentum among these planets, thus moving Mars to the
desired orbit. Conservation of both energy and angular momentum
requires that two other planets besides Mars be used.

A *tame asteroid* is one that makes repeated encounters with
planets that magnify small perturbations of its orbit. The object is
to achieve the goal of moving Mars with minimal total ,
i.e. minimal rocketry.

Moving Mars will take some tens of thousands of years, but not
millions of years.^{1}

- Chaos and controllability
- A tame asteroid
- Conservation of Energy and Angular Momentum
- A scheme with minimal total
- Differential equations
- Remarks and Acknowledgments
- Bibliography
- About this document ...

2007-10-06