In case you haven’t read it, there’s a great story on the surprising longevity of the two unmanned Mars rovers Spirit and Opportunity. They were designed to work for at least 90 days but they’re entering their third year of exploration.

One of the best quotes from the linked article:

The U.S. space agency NASA thought that the planet's extremely frigid temperatures and dusty atmosphere would keep their lives short. The dust was expected to build up on their solar panels, limiting their ability to recharge their batteries from the sun's energy.  But luckily, whirlwinds blew the dust away several times, extending their lives.


Isn’t that the best? Saved by dust devils! I don’t think I could have imagined a more awesome maintenance plan.

The whole endeavor makes me think of two impossibly distant kites, tethered on strings millions of miles long. I remember, as a child, giving so much string to a kite on a good windy day that I could hardly see the kite itself anymore, just the white parabola of the string disappearing into the shimmering sky.