From Earth to Moon — And Back Down Again — the Relentless Hunt for Dangerous Asteroids

Tonight a small robotic spacecraft named Lucy — after the famous “extraterrestrial” 400-million-year-old fossil — will take its first “handshake” with a target: a 1.4-mile asteroid.

The object is known as “31A,” or Trojan Star for short, and it’s to be traveling at 40,000 miles per hour (which is as fast as a Saturn rocket). Thirty-six-year-old Lucy is a telescope-guided craft — the first one capable of getting so close to a celestial body.

While most asteroids are dark, hard objects, 31A is a glowing, full-color “disc” that looks like a vast fossil pockmarked with “new” craters. Scientists have not yet realized the asteroid’s genesis.

It is not surprising that Lucy is going so fast — the surface of 31A is rarely subjected to sunlight, allowing for an incredible amount of distance between what scientists know (or “sight”) and what is “in the field of view” of the telescope (in this case, a 5-meter telescope in Puerto Rico). While scientists in space wonder about what 31A’s origin might be, Lucy will be breaking close to its dangerous neighbor.

“While Lucy was in our system we received reports of 27 near-Earth asteroids that passed closer than one Earth orbit,” said astronomer Michael Vickrey, of the University of Utah in Salt Lake City, where one of the US’s two Lucy-cores, on loan from NASA’s Jet Propulsion Laboratory, is based. “And 31A is one of the closest passes of any of those asteroids.”

While they are usually found within 90 million miles of the earth, 31A will come a mere five million miles away from us. That’s more than seven times the distance between Earth and the moon, which will come even closer — about 60 million miles — on Saturday.

People call these objects “dark” asteroids because of their weathered surface or low orbit, but this is rare. Once a handful are discovered, there are millions more that go undetected because they are so small. Today, NASA has a sort of watch-list. A recent report estimated that there are 2,000 dark asteroids and dark comets, a vast majority that could be lying within the asteroid belt.

But moon rocks find their way into our hands all the time — just this year, an orange-dusted chunk of rock weighing about 2 pounds was found on the moon.

As for the planning for 31A, it is not necessarily a spur-of-the-moment decision. A study of whether 31A was a threat was concluded with considerable deliberation before sending the craft there, and NASA will be reporting back on the asteroid’s motion and internal composition in five years.

“We have consulted with a lot of people,” said Vickrey. “We’ve had meetings with our international team and NASA. What has been really important is to give space missions a long-term strategy.”

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