This is a fun paper that shows there's a decent chance we don't have to go to Mars, because Mars may eventually come to us (thanks to instabilities in Mercury's orbit). We'd only need to put landing gear on the ISS. perso.imcce.fr/jacques-laskar… 
The authors ran a general relativity model on the Solar System extrapolated 5 billion years out. For each run, they changed the initial size of Mercury's orbit by a few millimeters. Since the Solar System is chaotic, this is enough to produce some spectacularly different outcomes
The upshot is—don't trust Mercury, especially when it's in retrograde. In many of these scenarios it gets pulled into a highly eccentric orbit by Jupiter, and then crashes into Venus or into the Sun. Add this to your list of anxieties if you feel optimistic about life extension.
I would like to hear from professional astrologers about the implications of Mercury falling into the Sun, or Venus and Earth swapping orbits. How would this affect your work? Have a plan.
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