This article at Slate says so, but there are some unfounded assumptions in it:

What should be NASA’s most important task — keeping the Earth, and America, safe from asteroid and comet impact — is barely mentioned in its latest strategic plan, released earlier this week. Planning for a mission to deflect a potential cataclysm is left to private organizations like the B612 Foundation, in which a number of engineers and scientists with years of experience with NASA are involved. It’s even headed by former astronaut Ed Lu. But this is too important a task to be left to philanthropists and retirees like the B612 crowd. However laudable their efforts, they lack the resources and capability that the government has. Keeping its citizens safe is the foundational responsibility of government. And in this respect, NASA has been heedless of its responsibilities.

This is just another example of “Space = NASA” thinking. In fact, the reason that there is nothing in NASA’s strategic plan about this is that it has no charter about planetary protection, and it is not currently its “responsibility.” If you think otherwise, go look at the Space Act, and tell me where it is.

In fact, it’s not at all clear that NASA is the right place for this to happen, particularly given all its chronic organizational dysfunction. I would submit that there is currently no government agency chartered to protect the planet. I think I’m going to write up an op-ed or two declaring that it’s time to fundamentally reorganize the federal space establishment, including the formation of the Space Guard.

[Update a while later]

To elaborate, let’s go into the objectives of the agency (just typing out loud here):

(1) The expansion of human knowledge of the Earth and of phenomena in the atmosphere and space.

(2) The improvement of the usefulness, performance, speed, safety, and efficiency of aeronautical and space vehicles.

(3) The development and operation of vehicles capable of carrying instruments, equipment, supplies, and living organisms through space.

(4) The establishment of long-range studies of the potential benefits to be gained from, the opportunities for, and the problems involved in the utilization of aeronautical and space activities for peaceful and scientific purposes.

(5) The preservation of the role of the United States as a leader in aeronautical and space science and technology and in the application thereof to the conduct of peaceful activities within and outside the atmosphere.

(6) The making available to agencies directly concerned with national defense of discoveries that have military value or significance, and the furnishing by such agencies, to the civilian agency established to direct and control nonmilitary aeronautical and space activities, of information as to discoveries which have value or significance to that agency.

(7) Cooperation by the United States with other nations and groups of nations in work done pursuant to this chapter and in the peaceful application of the results thereof.

(8) The most effective utilization of the scientific and engineering resources of the United States, with close cooperation among all interested agencies of the United States in order to avoid unnecessary duplication of effort, facilities, and equipment.

(9) The preservation of the United States preeminent position in aeronautics and space through research and technology development related to associated manufacturing processes.

Now (1) could clearly include looking for rogue asteroids.

(2) and (3) aren’t relevant.

(4) could potentially encompass looking into things like gravity tractors and other means of diversion, if you want to consider not being slammed by a space rock a “potential benefit,” but it doesn’t say that the agency would actually execute such plans.

(5) is too vague to be useful for this (as it always is).

(6) could include telling the DoD about asteroid diversion techniques, assuming that you consider diverting an asteroid a national defense activity, rather than simply managing nature (e.g., flood control or forest management to prevent major fires).

(7) could apply, but it would just be an excuse to get together with other countries to do whatever NASA wanted, not because it’s intrinsically in its wheelhouse.

(8) doesn’t really seem applicable, nor does (9) unless you consider learning how to herd asteroids the development of a new manufacturing process.

Really, folks, it wasn’t what Congress had in mind when they created the agency, and nothing they’ve done to amend it since has substantially changed that. If we’re serious about asteroids, we need to set up an agency that will be focused on that, and not diverted by a bunch of other politically driven things.

One other point. Ed Wright notes in comments: “The National Academy of Sciences bashed the idea of a manned asteroid mission in its recent report on NASA priorities. They see asteroids solely as objects of scientific study and believe unmanned missions are good enough for that.”

The other unfounded and unexamined assumption is that we too strongly correlate space with science. This is probably one of the biggest policy myths that has been holding us back for decades, because the whole idea of a civil space agency developed out of the International Geophysical Year in 1958, and since then, everyone has assumed that NASA’s primary job is to do science. It’s been almost impossible to break out of that mindset and think in terms of space development and settlement. I’m not sure that we’ll ever be able to sever the connection, so it would be better to establish new national goals for space, one of which would be planetary protection, but another would be to enable space commerce including transportation (e.g. search and rescue, constabulary duties, etc.), and set up a new agency (Space Guard) that won’t be distracted by “science” and about whom the National Academy will have nothing to say, to execute them.