I am working on uploading an annotated image of "Sleepy Hollow", showing the
last few bounces of the Spirit lander, encased in protective airbags.
Please be patient while I coerce the internet to do things for me in
this forlorn region in which I am currently marooned. Once it is up,
the discussion will make more sense, but if you're keen you can go
look at the original panoramas and make up your own minds....
There are several interesting things to be gleaned from this scene,
which perhaps indicate that things were a bit close to the mark on
the landing...
I recommend that you refer to larger original images to confirm the
details of the interpretation, but here is my take:-
The green ellipses are the more-or-less circular bounce marks. In the
centre, the ground was compressed vertically and appears little
changed, but around the rim it was sheared sideways as the airbags
spread under load, giving a "Fairy Ring" appearance of dark disturbed
dirt.
Notice first that the lander bounced into and around and then back
out of "Sleepy Hollow" before coming to rest at its current location.
This in itself is interesting. Sleepy hollow is ~WNW of the landing
site, so the lander was bouncing in a ~north-westerly direction. The
parachute descent photos show drift was in a SE or ESE direction -
directly opposite to this trend. This suggests that the lateral
rockets OVERcompensated for the drift and shot Spirit back in the
direction from which it came.
The next thing to notice is the irregular (one might prophetically
say "ragged") marks adjacent to the last few bounces (black arrows).
These, along with the difficulty encountered in fully retracting the
airbags suggest that at least one of the airbags punctured during the
landing sequence and was flapping uselessly as a loose bundle of
cloth, rather than protecting the lander.
In short, the Spirit lander appears to have used most of its safety
margin in various ways, before safely coming to rest.
Opportunity, take note...
One Bounce from Disaster?
