Congressional appropriators have rebuffed U.S. President Barack Obama’s request to allocate $30 million next year toward resuming domestic production of the nuclear fuel needed to power deep space missions like the Cassini spacecraft now orbiting Saturn. As a result, NASA faces a minimum one-year delay in the future availability of this critical material, creating uncertainty that will impede planning for missions to the outer planets and their moons, which are among the most intriguing objects in the solar system.

Members of the House and Senate appropriations committees, meeting in conference Sept. 30 to hash out differences in their respective 2010 funding bills for the U.S. Department of Energy, zeroed out the request for production of plutonium-238 (pu-238). This had been the Senate position going into the conference; the House version of the energy and water development appropriations bill would have provided $10 million.

The United States stopped making pu-238, the essential ingredient of long-lasting batteries used to power probes operating too far from the sun to draw on its energy, in the late 1980s, opting to rely on Russian stockpiles. However, Russia no longer produces the isotope, and its own supplies have been depleted. According to a U.S. National Research Council report released in May, NASA has access to sufficient quantities of the fuel — which also has unspecified national security applications — for its Mars Science Laboratory rover mission slated to launch in 2011, a flagship-class deep space mission to be launched around the end of next decade and a few smaller probes that need just a small amount of the material. The report said resuming U.S. production of the highly toxic material would be an eight-year process costing more than $150 million.

To its credit, the Obama administration acted quickly on the report, inserting $30 million into the U.S. Department of Energy’s 2010 budget request to begin re-establishing a domestic pu-238 production capability. The Energy Department, while not an end user of the material, is by U.S. law the domestic manufacturer and steward of all things nuclear.

Congressional appropriators appear to have issue with this longstanding arrangement, however. Both the House and Senate versions of the energy and water bill, while supportive in principle of resuming pu-238 production, raised questions about funding contributions by the consumer agencies: NASA and, presumably, the Pentagon or the intelligence community. The conference report directed the White House to include a cost-sharing plan in its 2011 budget request for the program. Considering that the money in question all comes from the same place, lawmakers could have gotten their point across another way. They could have fenced off a portion of the requested funding pending receipt of a report on the department’s plan to initiate pu-238 production, to include cost sharing arrangements, for example. Or, the conferees could have at least adopted the House position, which, while hardly ideal, was better than nothing.

Every delay at the front end of the long process of resuming pu-238 production will defer what Congress and the White House agree is an important national capability, both for national security and scientific purposes. Although there are no specific NASA missions approved yet that would require new stocks of pu-238, uncertainty about when the material might become available will complicate planning for such missions. One can envision a self-perpetuating cycle whereby missions won’t get planned or funded because of questions surrounding pu-238 availability, thereby making it easier — and in a perverse way, logical — to continue deferring its production.

In fact, the National Research Council report said the pu-238 issue already was putting a crimp in NASA’s deep space exploration planning.

The Obama administration made an appeal to Congress when it became clear that its request for pu-238 production was in jeopardy. In a so-called statement of administration policy issued in July in response to the Senate’s version of the bill, the White House said it “strongly urges the Congress to restore funding to re-establish a domestic Pu-238 production capability, which is essential to make sure Pu-238 will be available when needed for planned NASA missions as well as future national security applications.”

That appeal fell on deaf ears, which is unfortunate, especially since lawmakers know full well that domestic production of pu-238 will have to be restarted sooner or later. In an all-too common display of posturing and short-sightedness, congressional appropriators have chosen later, never mind the fact that the consequences of inaction are already being felt.