For the past month, severe Martian summer dust storms have affected the two Mars rovers: Opportunity and Spirit.

Pictured above is a time-lapse composite of the darkening horizon by Opportunity, where storms have blocked 99% of direct sunlight to the rover. Meanwhile, Spirit is in a location that's less severe. The rovers have been instructed to conserve power by limiting activities. Both rovers are depending on diffused sunlight to charge their batteries.

It's possible that both rovers may be damaged permanently or even disabled by the storms. Engineers will assess the capability of each rover after the storm clears - which could be in days or weeks.

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