Today's the last planning day for both rovers before solar conjunction. We're all excited because we're uploading 15 days of plans to each rover to conduct all on their own, then we'll get to drink from the firehose of data return in the last week of October!
The Mossbauer team is excited that we'll be using this chance to collect some fantastic Mossbauer integrations. The Mossbauer spectrometer works by exciting the sample with gamma rays and measuring the emmision and absorption response of the sample. The gamma ray energy on the rovers' Mossbauer spectrometer is tuned to iron, so that the response is a fingerprint of the iron-bearing minerals in the sample we're looking at. This is good because so much of Mars is iron-rich, so the Mossbauer mineralogy has been very useful. But, the Mossbauer source natually decays, and at more than 10 times its expected lifetime, the MB source is fairly weak. This means that to get a good signal-to-noise ratio, we need to leave the MB on a target for something like 48 hours to even get the major mineralogy. To tease out the fine details, it needs more time, and we're almost never able to give it that time before moving on - until now. Both rovers have more than 10 days of Mossbauer spectrometry planned over conjunction. Spirit is looking at her magnet, which has collected magnetic dust along its traverse, to look at what iron-bearing minerals make up the Martian dust from the atmosphere and the ground that gets kicked up by wind. Opportunity is looking at a patch of rock at Victoria crater and I'm super-excited to see what minerals it can find in the rock here!
While we're letting the rovers do their own thing during conjunction, their timers will roll over sol 1000! Since nobody expected them to live this long, much of their software was built to only accept 3-digit sols (up to 999). It's like Y2K for the rover - quick, buy some bottled water and duct tape! The ground and flight software engineers did a fabulous job of either fixing or working around this issue and testing it thoroughly, so we don't expect any problems. Still, I feel like when we next see our little friends, they'll have passed this major milestone.