Tests of similar rovers in Earth deserts (including Athena's Earthbound near-twin "FIDO") have confirmed the extreme importance of doing this to maximize the rover's scientific value.

But the descent camera has been dropped from this mission due partly to the difficulty of integrating such a camera into the new lander, surrounded by its huge mass of inflated airbags.

But the main reason is that the lander (like Pathfinder) will bounce and roll up to a kilometer from its original touchdown point -- and so any camera with a wide enough viewfield to be sure of mapping the actual area which the rover will explore would have such low resolution that the earlier photos taken of the landing region from orbit by Mars Global Surveyor's very high-powered telephoto camera will be almost as sharp.

When it finally edges to a stop just in front of a rock, the rover can analyze it with five different instruments -- but a sixth one will probably have to get the boot.

Athena was originally scheduled to carry a "Raman spectrometer", an instrument that takes spectra of the light scattered off a mineral specimen from a tiny laser beam and can thus identify a great variety of minerals. And it can also detect organic compounds with great sensitivity -- the only Athena instrument that could do so.

But the revised version of Athena for this mission has to carry more communications equipment than had been planned. Originally Athena was not supposed to carry any direct radio link with Earth -- it would have communicated entirely indirectly, during 10-minute exchanges every time a Mars-orbiting spacecraft with a radio relay system sailed overhead.

But the failure of Mars Climate Orbiter removed one of the orbiting com relays the mission had been counting on -- and the tiny Mars Micromission comsat that was supposed to be separately launched in 2003 has now been delayed until at least 2005, again for budget reasons.

Unless Mars Global Surveyor is still working after six years (and its radio link is only one-way; it can't relay Earth commands to the rover), there will be, at absolute most, only two relay satellites for it: the 2001 Mars Surveyor orbiter, and Europe's Mars Express spacecraft also scheduled for 2003.

And if both of those fail, the rover would be helpless unless it had a slower, backup direct radio link to Earth -- which it has: an X-band system with a pointable dish antenna like the one on Mars Polar Lander, which will allow it to receive orders from Earth for half of each day and also transmit a good deal of science data even if the relay orbiters aren't around.

But this new system takes up added room in Athena's body -- and it's almost impossible to enlarge that body and still fit it inside the Pathfinder landing system, whose dimensions they don't want to change.