WASHINGTON — Legislators posed a difficult hypothetical to NASA officials Tuesday: What could we do if we found out there was a meteor on a collision course with Earth, and it was only three weeks from slamming into the planet?

"Pray," was the answer from NASA chief Charles Bolden, speaking Tuesday before a the House Committee on Science, Space and Technology.

Scientists have virtually no way of detecting some of the smaller asteroids and meteors that cross the orbit of our planet, things the size of the meteor that exploded over a Russian city in February, injuring more than 1,000 people. The same day, as 150-foot asteroid known as 2012 DA14 flew within a few thousand kilometers of Earth.

While there are systems in place to detect larger objects — the kinds of things that could vaporize a continent or end all life on the planet — small objects are another matter. Still, those "small" objects can cause devastation. According to Donald Yeomans, leader of NASA's near-earth object program, the meteor that exploded over Chelyabinsk could have hit the city with the force of 20 Hiroshima bombs.

"The reason I can't do anything in the next three weeks is because for decades we have put it off," Bolden told the Committee Tuesday.

In 2005, NASA was directed to detect and catalogue at least 90 percent of objects over 87 miles in diameter. The have reached about 10 percent of that goal. Bolden also blamed lack of funding for the lack of an early-warning system and for the lack of a catalogue of large near-earth objects. He said the "bottom line is, the funding did not come."

"Our estimate right now is, at the present budget levels it will be 2030 before we're able to reach the 90-percent level as prescribed by Congress," Bolden said.

Related:

Asteroid buzzes, misses Earth — unlike meteor

A 150-foot asteroid hurtled through Earth's backyard Friday, coming within an incredible 17,150 miles and making the closest known flyby for a rock of its size. In a chilling coincidence, a meteor exploded above Russia just hours before the asteroid zoomed past the planet.

That fact caused dismay among some congressmen, with Rep. Lamar Smith, R-Texas, saying he was not reassured by the 10 percent figure. Meteors as large as 87 miles would cause utter global devastation. But even meteors as small as 100 to 150 meters could level a city and kill millions of people.

Any chance of a strike is small — but the risks are still there.

"The odds of a near-Earth object strike causing massive casualties and destruction of infrastructure are very small," said John Holdren, a science advisor to President Obama. "But the potential consequences of such an event are so large that it makes sense to take the risk seriously."

Holdren said it would cost roughly $100 million each year to set up and maintain a detection system in orbit. Actually stopping an asteroid, including the possibility of a manned trip to an asteroid, would cost roughly $2 billion in the next 12 years, he said.

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