Spirits problems began in 2007, when one of its six wheels seized up, making movement difficult.  Serendipitously, the dragging of that wheel dug a shallow trench in the Martian surface, revealing almost pure silica deposits beneath the surface – a significant discovery, as it was a sign that that region of Mars used to be very wet and was likely underwater at some point in the past.  In 2010, the rover got stuck when it broke through the thin crust beneath its wheels and sank into the soft sand below.  The rover was not only immobilised, but was left tilted at an angle that left its solar panels pointing away from the Sun.  As they were already coated with dust, and the long Martian winter was approaching, the mission scientists knew that Spirit was unlikely to have enough power to keep its internal heaters running.  Since it was never designed to survive such intense cold, this was an almost certain death sentence for Spirit.  But they remained hopeful, despite the poor odds.  As soon as the weather began improving, a program was started to attempt to communicate with the rover, in case it had survived the winter and come out of Hibernation.

Unfortunately, we have received no response in all these last ten months, and so it is with much sadness that we bid farewell to Spirit.  May the forthcoming Curiosity rover match the exceptional standards set by its predecessor!