It only took that long because MGS was aerobraking into orbit and wasn't designed to survive the stress of lower atmosphere turbulence, so only used the uppermost layer of the atmosphere for braking. If your going to land, obviously you get to use all the atmosphere and also can use parachutes. Something a problem braking into orbit can't do.
Surface probes do direct descent trajectories. There is no extended series of repeated braking passes. You do it in one go.
Re:Water Found Deep Inside the Moon
by dragonwriter on Thursday August 24, 2017 @06:48PM
(#15094737)
> If your going to land, obviously you get to use all the atmosphere and also can use parachutes. Something a problem braking into orbit can't do.
Also, you can use lithobraking.
It took MGS 15 months (not counting delays) of aerobraking to do that. MGS only weighed 1000kg too. Maybe it could work for shipping large, pre-assembled, empty hab modules to Mars before people get there. (Low density, higher drag, no rush.) But not practical for actual human bodies or even resupply since the Hohmann transfer takes a mere 8.5 months. Adding an aerobraking maneuver could easily triple the transit time.