I think it's kind of surprising how low the number is. Almost certainly because space exploration is underfunded.<p>Over the last few weeks, there has been a lot of talk about the NASA budget, and there are a couple of things I think many people don't know. The total 2010 US Space budget was $64.6B. The entire rest of the world combined spent only $22.5B. NASA's 2010 budget was $18.7B, 83% of the spending for the rest of the world. It's more than a little ironic when those outside the United States criticize cuts to US space spending. Europeans, in particular, may want to consider the paltry $4.6B ESA budget before they criticize the United States. Space spending does need to increase; the rest of the worlds needs to start contributing.