It seems every time I come across a story about the Mars Curiosity rover there will be many people commenting on the technology used starting with "Why don't they just..?" and usually pointing out things like: the processor in their smart phone is way faster than the one of Mars, or they have way more memory on their iPad, or their digital camera is way better than the one sending back pictures. These "Why don't they just..?" questions are both annoying and to be expected.Annoying because the underlying thought is "Those NASA/JPL guys are so dumb LOL" and to be expected and encouraged because we wouldn't make any progress without asking questions and, in particular, asking why.But it doesn't take much research to find the answer. (Even though I'm tempted to answer: "Because it's on friggin' Mars, doofus!")1. The Mars Science Laboratory project was started eight years ago in 2004. So, all the technology on it is at least eight years old.2. The trip to Mars means flying in an area with high amount of radiation (from things like cosmic rays all manner of stuff flying out of the Sun and the Van Allen radiation belt ). That means all the electronics needs to be radiation hardened . So, you don't start with just whatever you can get from Fry's Electronics in 2004. You need specifically radiation hardened components like the RAD750 processor in Curiosity.3. You need to be a bit conservative. The thing you're sending to Mars is going to be on its own and unrepairable. It had better work. So, you're likely to reuse components and techniques that you know work. It has been reported that the skycrane used to land Curiosity used components derived from the 1970s Viking landers and algorithms used on the Apollo craft.4. And once you've worried about radiation hardening, reliability, and weight you need to worry about bandwidth back to earth. It's no good taking gigapixel photographs if you can't get them back to Earth. For example, Curiosity can communicate with the Mars Reconnaissance Orbiter for a few minutes per day at 2Mbps and with Mars Odyssey at 256kbps.But rather than explaining all this stuff, I think there's a better way: build, land and operate a rover here on Earth.I've done one high-altitude balloon flight and watched the progress of many others. Although going to Mars is a very different situation there are similar challenges: weight, environment, communications, landing.A good way to see how hard it is to build and operate a rover would be to build one designed for operation in an inhospitable part of Earth. Launch it via a high-altitude balloon with parachute descent and then operate it without GPS over a slow, high latency radio link.It would actually be a fun project. On a balloon you can probably have about 2kg of payload maximum for your rover. Now imagine 2kg weight budget for a semi-autonomous rover that would be dropped into a desert in the South Western USA, or the Sahara, or the Australian outback.The rover would have to withstand high tempertures, dust, and wind; operate on a perhaps unstable sandy ground; communicate using HF radio; and operate without a human touching it.To me it sounds like a fun challenge. Anyone else?