Explain some of the advantages of unmanned space missions over manned space missions?

First of all, unmanned space flights are a lot less-risky. Even in our advanced civilization space flight is still not a easy feat.

Robotic probes and rovers can operate for a longer period on less energy, they are a lot cheaper, requires no food, no water, no plumbing and is generally a lot easier to operate.

The disadvantages of unmanned space missions are obvious, six years of exploration of two rovers could be done in 1-2 weeks by astronauts. Astronauts can improvise on the spot, where as the rovers for example has limited movement, and the option for problem solving is limited to the array of equipment specially designed for each little operation.

The rover Spirit have been irrecoverably stuck since 2009 in soft soil. But it is still a great success, operation freely for 1944 days, versus the predicted 92 days.