by Matt Tarlach
Herodotus and Schroter's Valley have been well lit for the past few hours (around 0400 UT on June 14, 2000). I've been viewing with the 80mm Vixen, under conditions of poor seeing that only allow about 100-140x. Still, it's apparent that the eastern wall of the Valley, at least the first 30km or so coming down from the Cobra's Head, is in fact a ridge with higher elevation than the terrain outside the valley. That first, widest part of the Valley appears as a double bright line, with darkness between....I interpret the bright eastern line as a ridge marking the Valley's edge. Valley walls further north and west may also be ridged; it's impossible to see under the current seeing conditions. I'll check again after posting this.
My limited understanding of the sinous rilles (of which Schroter's Valley is an outsized example, correct?) is that they are collapsed lava tubes. If the Valley wall is a ridge, it would seem more likely that the Valley had been excavated in some way, rather than formed via collapse. Any thoughts?
On my way out again, to watch sunrise on Wargentin.