One Mars spacecraft, two senators, and a cloud of questions

NASA released a much-anticipated contract solicitation for a Mars-orbiting spacecraft late last week, kicking off what is sure to be a hotly contested and potentially controversial procurement. At issue is $700 million, already appropriated by Congress, to build a spacecraft, launch it to Mars, and once there to serve as a vehicle to relay communications between the red planet and Earth. But the stakes may be even bigger than this, including the possible resurrection of the recently canceled Mar