NASA is putting the number of potentially hazardous asteroids and comets at 20,000 in a report that will be released later this week, according to an AP story now circulating. And the report, reviewed at a Planetary Defense Conference in Washington yesterday, pegs the cost of finding 90 percent of these objects at $1 billion. That’s bad news for those worried about Earth-crossers. For AP quotes NASA Ames director Simon Worden: “We know what to do; we just don’t have the money.”

And as Larry Klaes wrote me this morning, “But just imagine the bill after a big space rock hits Earth.” NASA is already tracking some 769 objects in a search now described as behind schedule. From the story:

One solution would be to build a new ground telescope solely for the asteroid hunt, and piggyback that use with other agencies’ telescopes for a total of $800 million. Another would be to launch a space infrared telescope that could do the job faster for $1.1 billion. But NASA program scientist Lindley Johnson said NASA and the White House called both those choices too costly.

A cheaper option would be to simply piggyback on other agencies’ telescopes, a cost of about $300 million, also rejected, Johnson said.

“The decision of the agency is we just can’t do anything about it right now,” he added.

Deflection, which we often discuss in these pages, isn’t an option for objects we never see in the first place. Shouldn’t asteroid tracking receive higher budgetary priority? The public, perhaps jaded by alarmist rhetoric on too many fronts, seems to perceive this as only a science fiction scenario. Yet the real dimension of the threat won’t be known until we map the dangerous Earth-crossing materials and know where we stand.