NASA Abandons Asteroid Capture Dreams, Will Settle for a Boulder

"I'm going to have multiple targets when I get there, is what it boils down to," Lightfoot said. "That was the better value, in my opinion, for what we're trying to do."

It's also important to note that while the boulder approach will cost an estimated $1.25 billion, the Moon orbit scenario had its own additional costs that could have pushed the agency's wallet. After the small asteroid was successfully redirected, NASA would still have to drop the cash for additional launches to put equipment-toting astronauts on it.

Still, some experts are skeptical that any ARM is worth any cost at all. After all, NASA and Canada are already invested in the OSIRIS-REx mission, which aims to return about 60 grams of samples from the asteroid Bennu by 2023. And Bennu also happens to be one of the three asteroid candidates that NASA is considering for the ARM.

Meanwhile, JAXA, Japan's space agency, just launched Hayubusa 2, which will be bringing several grams of asteroidal material back to Earth in 2020.

It may be that NASA has its hands in too many cookie jars at one time. We won't know for sure that ARM will be worth it until results are in - long after the mission's spacecraft returns with a big old hunk of space rock in tow.

For more great nature science stories and general news, please visit our sister site, Headlines and Global News (HNGN).

- follow Brian on Twitter @BS_ButNoBS