Things aren't looking good for the Opportunity Mars rover as the global dust storm socking the Red Planet looks set to continue into September. Mission control at the Jet Propulsion Laboratory (JPL) in California is continuing a daily listening brief in hopes that the unmanned explorer will radio home, but no response has been heard since June 18. So long as the storm cuts off sunlight, Opportunity's solar panels are unable to generate power to recharge its batteries.
The fate of Opportunity is a very much a matter of guesswork, though NASA remains cautiously optimistic. The rover was only designed to operate on the Martian surface for 90 days, but has had its mission extended by 15 years, so it's working well outside of its engineering envelope. This means it has suffered 15 years of wear and tear, but it also indicates that Opportunity is over-engineered, which works in its favor.
On the other hand, the global dust storm is also an unknown. Such storms weren't confirmed until the Mariner 9 mission arrived in Mars orbit in 1971, and they aren't exactly common. Showing up about once every six to eight Earth years, there hasn't been time to gather much data on how they form or how long they last. However, the current storm that was first seen on May 30 and went global by June 20 is similar to the one that broke in 2001, suggesting it could run through to early September.
This is not good for Opportunity, which relies entirely on its solar panels for power. The storm has blasted a very fine dust high into the Martian atmosphere, where it has cut off so much the available sunlight (which isn't much on Mars to begin with) to such a level that the panels can't charge the rover's batteries. This means that Opportunity can't move, power its primary systems, send signals to Earth, or run the heaters needed keep its electronics from freezing and permanently disabling it.
NASA says that the one bright spot is that the dust is acting as an insulator, so the ambient temperature might not fall below Opportunity's design levels. Unfortunately, the darkness has been so deep and so prolonged that the rover can't even run its mission clock and must await the storm's end before it can charge enough to recontact Earth.
When that will be is difficult to say because such charging could take weeks or even months after the dust settles. Worse, the dust might come to rest on the panels. This isn't a terminal problem because the dust is so fine and experience has shown that a slight gust will blow it back off, but it is another delaying factor.
The video below shows the Martian dust storm before and after breaking.
Source: NASA