Since their launch last summer, I've been very interested in the Mars Exploration Rover missions. It's great to see not only that they have successfully landed and retrieved useful scientific data, but also that the hypotheses of the principal investigators are turning out to be correct! It looks like there was actually standing water on the surface of Mars, and that is a phenomenal discovery.

The Planetary Society put a DVD on each rover that has thousands of names burned onto it. A couple of years back you could sign up to have your name sent to Mars. A little cheesy, but... mine name is on there, so is Nina's. Just for fun, they encoded some messages on the labels of the DVDs so that when the rovers took pictures of the discs from Mars, you could look at the images and decode the messages. It was a sort of a contest.

First to land was Spirit, and the picture of its DVD message is here:
https://planetary.org/redrover-dvd/dvd_spirit.html

Then came Opportunity, and its DVD picture is here:
https://planetary.org/redrover-dvd/dvd_opportunity.html

The two codes are wildly different. For some reason, Spirit's cypher is considerably more complex. The contest was designed for children, but I found the Spirit code to be a good challenge [before the clues were released]. It took me about three hours of work to unravel it. The Opportunity code was very simple, and only took about five minutes to solve.

I'll forego an in-depth description of the encoding systems used until they release the answers. So more on this later.