re: airbags vs. Viking
Developing a "smart" retrorocket landing system is a big priority for the 2009 super-rover, I believe.
.. didn't know that ..
it will have to have superb imaging & superfast processing (& super-responsive hardware) - as (i suppose) any horizontal manoevring will have to be done in the final moments. - A bit like Armstrong pointing Eagle away from that pile of rocks, but WITHOUT the highly-trained humans .. hmm - I hope it can be done..