[pmoriarty]

To me, the air bags[1] used to land the Spirit and Opportunity rovers seemed like a saner way to go than trying to deposit them gently directly on to the surface using a sky crane. The reported reason the sky crane was used for Curiosity is that it was too heavy for the air bag approach.

[1] - https://www.youtube.com/watch?v=XRCIzZHpFtY

[danbruc]

It's 185 kg vs 899 kg. I am already a bit surprised that it worked to land Spirit and Opportunity, but the lower gravity probably helps.

[Sharlin]

But the Spirit and Opportunity EDL also involved retrorockets in addition to a heatshield, a drogue chute, a parachute and the airbags - it's just that the retrorocket part didn't have to be as precise as with Curiosity.