Can we use drones for planetary exploration.
Rovers have the inherent problem of getting stuck in terrain. and have limited range. why have space agencies not considered the use of drones for exploring a planet.
If you are talking about flying drones, then the answer is that we haven't tried to explore a body with a suitable atmosphere yet. Mars' atmosphere is so thin that a winged drone is difficult to engineer. I believe such a thing has been proposed, but there are a lot of easier missions NASA (and other agencies) would want to try first. And Mars is the only body beyond the moon that we have even placed a rover on.
But, as for other bodies, Venus is so hot that a drone flying low enough to observe the surface well would be nearly impossible to engineer. Even stationary landers have only ever lasted a few tens of minutes.
Titan is quite cold, but gravity is low and the atmosphere is thicker than Earth's. I bet it could be made to work, but Titan is very far away and we won't be sending probes there very often.
The gas giants are probably better candidates to be explored by dirigibles, but that would be an expensive mission.
NASA have considered underwater drones for exploring Europa
If you're looking for flying drones, NASA is currently developing a flying scout to accompany a driving rover. This scout would have only a couple of minutes of flight time a day and take a while to recharge.
However, let's just say we are designing a similar drone for martian exploration, lets consider some of the advantages and disadvantages we have, specifically on mars.
In short, I think that there are certain valuable applications for a flying drone on mars (or other planets) and they will be used but only when there's people there to pick it up if it lands on its side. Right now, putting a drone on the surface of mars would be extremely expensive and high risk to gather data that could be gathered just as well abet at a slower pace (driving rover or high resolution satellite imagery).