In most cases, the instruments we
send to Mars
are essentially revamped versions of experiments
we have sent to Mars before, but with
better technology.
Microscopes and
digging tools are new, and hold
the possibility of independently testing
the Viking results, in theory.
How the new data relates to, supports,
or contradicts the Viking biology experiments
remains to be seen. It appears that
it is not a high priority for NASA to
confirm/reject the various hypotheses derived
from the Viking biology experiment data.
Instead, NASA is concentrating on looking
for (and finding!) evidence of past water
on Mars.
This is certainly an interesting conclusion,
but one gets the sense a little bit that
NASA has backed off from the very difficult
biology experiments, in part because it might
be too difficult to draw a solid conclusion
one way or the other.