For the last six weeks the Spirit and Opportunity rovers on Mars have been out of commission due to a huge planet-wide dust storm. The dust probably is not the best thing for electronics, but the real problem was the lack of sunlight. Both Spirit and Opportunity are solar powered.

But we got good news earlier this week – as the storm has slacked off both rovers have checked out as okay.

When the severity of the storms became clear, mission managers elected to have the craft hibernate to ride it out. Then, earlier this week, NASA said the craft could resume their exploration.

Although the skies are now clearer, it will also take some time for the skies to clear properly, as project scientist Bruce Banerdt explains: “The clearing could take months. There is a lot of very fine material suspended high in the atmosphere.”

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Both rovers are now generating around 300 watt hours from their panels. This is more than twice as much as five weeks ago, but less than half the output prior to the storm.

Both the Spirit and the Opportunity were built with a three month active lifetime in mind. I guess NASA was being cautious because both rovers just surpassed the milestone of 1281 Sols – the service life of Viking 2. Only Viking 1 has operated on Mars longer – 2245 Sols.

Both Viking 1 and 2 were nuclear powered – and expensive. The combined cost of both the Spirit and the Opportunity is $820 million – less than a fourth of the inflation adjusted cost of the two Viking missions.

The Viking probes weren’t subject to power failure in sand storms, but they were immobile.

On Mars… advantage solar.