QUESTION:
Both Mars Pathfinder and Mars Gobal Surveyor used aerobraking techniques to
reduce the fuel mass needed when they arrived on Mars.

Just how much delta velocity is needed for MOI into Low Mars Orbit, or
direct descent to the surface?

How much mass was saved? Would the missions have been possible (using Delta
rocket launches) if rockets had been used instead of aerobraking?

I heard the Mars Surveyor MOI burn was 973 m/s but not how much additional
delta velocity will be provided by the aerobraking over the coming months?

ANSWER from Charles Whetsel on October 31, 1997:
To reach the final mapping orbit without aerobraking, the MGS spacecraft
would have needed roughly twice as much rocket propulsion capability (fuel)
as it currently carries.  The spacecraft "dry" mass (not counting fuel) is
approx. 700 kg and the fuel load is about 350 kg.  If aerobraking had not
been used on MGS, the launch mass would have risen from 1050 kg to 1500 kg
and would have had to use an Atlas launch vehicle instead of a Delta.  The
total mission propulsion capability is appr. 1200 m/s, most of which was
used at MOI.  The aerobraking rougly provides the equivalent of an
additional 1000 m/s.

For anything descending to the surface of Mars "aerobraking" is required,
not optional.  "Direct descent" to the surface of Mars is not feasible like
the Apollo space capsules landing on the moon.  Pathfinder had both a
atmospheric heat shield and a parachute before deploying the airbags on
which it ultimately landed.  The Mars lander to be launched in late 1998
will descend through the top of the Martian atmosphere just like Pathfinder
(heat shield, then parachutes) until it is almost at the surface and then it
will use rockets to slow it's descent for the last few kilometers before
landing.  The weight of the rocket system on Mars Surveyor '98 is slightly
lighter than the airbags on Pathfinder, but it needs to land in an area that
is less rocky than the places where Pathfinder could land with the airbags.