From what I've been able to piece together, the final two candidate landing sites for the Mars Surveyor 2001 lander (which, of course, was canceled after MPL failed) were the Isidis Rim and what was then being called "the Hematite site" in Sinus Meridiani -- in other words, the site eventually selected for MER-B.

Can you imagine what would have happened had they sent an immobile lander to Meridiani and it landed out in the middle of the flat, featureless plains? With no outcrop in direct line of site?

We would have identified the blueberries as the source of the hematite seen from orbit, but would have had little to no clue as to how the blueberries had formed -- we would never even have seen the evaporite with the concretions eroding out of it. We would have no clue whatsoever that the dark mantling was the debris left over from the erosion of the soft, salty evaporite rocks, which would have left us without an all-important context for the soils we could observe from the lander. (Yes, I know the 2001 lander would have carried Marie Curie, Sojourner's back-up, but depending on where it landed, evaporite outcrop could well have been completely out of reach of the second Brave Little Toaster on Mars, as well...)

So, MER-B would have been sent somewhere else, and our understanding of Mars would possibly be a whole lot less developed than it is right now.

I guess the point I'm making is that the failure of MPL might have been a blessing in disguise -- it led to a chain of events that put the right instrument on the ground in the right place, which might well not have happened had MPL worked and the 2001 lander been sent to Meridiani.

-the other Doug

I agree, in a sense, the failure of the 2 spacecraft was a benefit for Mars exploration. IMHO any non-mobile lander has much less interest than a rover. We have become "spoiled" by seeing the versatility of the MER's and so when Pheonix lands I think we will be interested for a few days, but then as the same images / data comes back day after day, our interest will wane. Like Viking, we will want to know what is just over the next hill/behind the rock etc, but will never be able to reach it.

Going forward I dont see how we (or other nations) will send anything but rovers (unless very low cost Net-landers / penetrators).

Well, with Phoenix, it depends what it finds. Remember, rather than roving, it will spend its days digging a hole. Could be quite interesting (and make a great little movie).

And clearly, Phoenix will not last as long as the MERs because of it's landing site in the norh polar region. When winter comes it will be game over.

How deep will it dig into the ground?

True, but the rovers have already demonstrated that they can do some digging too, intentionally or not.

Maybe something like a mobile oil drilling platform? Only, not for oil of course.

A half a meter or so. It may hit ice. True, the imaging would be nearly as interesting as the MERs after the first few days, in the sense that the scenery won't change. But this is more of a chemistry mission. I wouldn't think it a good idea if you added up its total cost. But considering the money to build the thing was already spent on the '01 mission, I think it is a great choice. I hope this doesn't get us spoiled. The science on most scouts will probably be smaller scale, particularly for landers (if there are any).

The still rather speculative ESA rover mission is slated to have a drill, too...

The rovers should have had a very simple backhoe. But the rovers are as big and heavy and outfitted as it was possible to get on the budget and launch vehicle they flew on. So every time we wish for something else on the MER rovers, we have to ask what we would take off them in exchange.

Phoenix is a limited mission, but loaded with more science than you can fit on the MER rovers. The hardware for roving takes a major fraction of the landed mass and volume.

There will be many landers put down on Mars that are stationary. The Marsnet that the europeans abandoned because of $ would have been fine missions. We *NEED* a network of "indefinite lifespan" meteorological/geophysical landers. Full weather stations, dedicated cloud-cams, magnetometer and seismometer networks. Sure....Include a regular camera to assay the site and monitor changes, etc. But there's major needed science from stationary network landers.