I’m not normally a big agitator for unmanned planetary missions. I’m not opposed to them, but I don’t find them all that urgent and compelling. Generally, I agree with Proxmire’s famous statement, “Mars will still be there…”

But in this case I think that the cancellation of this particular mission is a travesty and a tragedy. In the context of the total NASA budget, a mission to Pluto doesn’t cost that much, and it’s one of the cases in which it isn’t true that “it will still be there.” Pluto has an orbit such that it will get much more difficult to reach it if the launch doesn’t occur in the next few years, perhaps to the point that it will be decades before we have an opportunity to explore it (assuming, of course, no major advances in deep-space propulsion, admittedly a brave assumption).

Unfortunately, the problems aren’t just penny pinching–they’re political (what a surprise–politics in a government space program). First, they’ve designed to launch the mission on a new launch vehicle that may not be adequately tested to NASA’s satisfaction by the time the launch window closes. This problem could be resolved by using a Russian launcher, but that’s not poltically acceptable.

The other problem is that a mission that far away from the sun can only be done with a nuclear power source, called a radioisotope thermal generator (RTG). This isn’t a reactor–it’s just a lump of plutonium that generates heat as it decays, which is then converted to electricity. We’ve been using such power sources safely since the beginning if the space program, but the last few missions that required such power sources (most notably the Cassini mission to Saturn) have had to run a gauntlet of environmental approvals and hysterical and ignorant protestors, and there is fear that the delays from this for the Pluto mission could end up pushing it out beyond its date of viability.

So, barring some technological breakthrough, we may not see Pluto up close for many decades.