Gusev:

Horizon distance in km is given from height in m by:
d=3.53*h^0.5

The crater has a diameter of 165 Km and a typical rim height above the crater plains of 2.1 km. On Earth, the horizon as seen from a human perspective near ground level is at about 5 km, on a billiard-ball smooth plain. Mars has half the diameter, twice the curvature, so the horizon is a mere 2.5 km away. Hills disappear twice as fast as they do on Earth.

From the rim one side of Gusev crater, you wouldn't see the other side. In fact, it would seem almost as if you stood on a near-linear cliff extending to infinity to either side of you, not a circular rim, at all!

(The landing site is over 50 km from the rim)

Isidis: I wouldn't quibble with 1 in 5 of seeing a cone.

All landings:

it is a manifest truth that if we had known the rockiness of VL1, VL2 and PF sites, we would not have been allowed to land there with modern safety standards. Look at VL1 - the rocks are bigger than the sub-frame clearance of the lander. We got lucky. Maybe that Russian lander that is supposed to have fallen over hit a rock?

Trafficability:

look on the bright side. If there are fewer rocks, we can travel further without working through a maze of rocks, and maybe drive up to the crest of some low hills and see further?

Aircraft:

I've been dismissive in the past of a mission that flies for 6 months to Mars, then returns 45 minutes, or at most 3 hours of video before crashing in a heap.

However, I recognise the value of oblique perspectives on some of these features, and of seeing details emerge from background context, enlarge, and become foreground features with their own layers of detail.

I would prefer a balloon to an aircraft, unmless we can send a nuclear or solar-powered one that would fly for days to weeks. Also, we need that high-speed data link to exploit the video opportunity.

I'd hate to send a video-equipped aerial platform to Mars, then make budget cuts on the Tellecom side and send back a series of still photos every 5 minutes, blurred to hell becuse they designed the camera for moving video, not still clarity!