What caused the "canals" on Mars?
On Mars, what is the Valles Marinas? How big is it?
Was there ever volcanism on Venus? What is the evidence for this?
Was there ever volcanism on the Moon? What is the evidence for this?
What is the supposed cause of the volcanic activity on Jupiterís moon Io?
What is the major geological feature of Mimas? What caused it?
What and where is Olympus Mons? How big is it?
Why are there far fewer craters on Mars than on Mercury?
Why canít we see surface features on Venus? How then do we know that the surface of Venus looks like?
What are scarps on Mercury? What do scientists think caused them?
What causes Marsí polar caps to change size periodically?
What is the origin of Marsí moons? What evidence makes scientists suspect that?
What are those spindly lines on Europa? What do they tell us about the composition of Europa?
What caused the grooved terrain on Ganymede?
What is the cause of the concentric rings on Callisto?
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