Why does the $2.5 billion Curiosity use a 2-megapixel camera?

When you consider how far and over how low-bandwidth a link each bit of data must travel, a geek's first question should really be why it uses so many pixels, not so few.

Another salient point is that pixel density/sensitivity aren't just a cost and time tradeoff, they are actually a direct technology tradeoff. Biger cells collect more photons and have less noise at higher effective sensitivities.

when not forgetting that #megapixels isn't everything, this is not so strange.. There's also pixel quality, dynamic range, ADC quality, lenses etc. High-end 10 year old cameras using 'only' 10 megapixels still take much, much better quality images than any brand new 40 MP smartphone camera.