May 23, 2007, HiRISE release Options

[Guest_AlexBlackwell_*]

May 23, 2007, HiRISE release

[marswiggle]

While I don't know, let them answer, in that very report:

However, a fortunate
MOC observation of Dena at ~2 p.m. (R0800159)
actually does show an illuminated floor, allowing us to
tightly constrain the depth using a 1-D photoclinometry
routine. This routine returns a depth of ~130 m for
the illuminated floor, while the minimum depth estimated
from the THEMIS observation is only ~80 m.
Because THEMIS IR observes at 100-m resolution,
cavern skylights with diameters much smaller
than that are probably not thermally distinguishable
from regular temperature variations on the surface

(The last paragraph also explains why the possible new skylight in S0901483 has not been observed with THEMIS, it evidently and perceivably being less than 100 m in diameter.)