A Second Moon

In the late 1960s and early 1970s, NASA astronauts brought 842 pounds of rock and soil from the Moon to Earth. In addition to those samples, scientists have found more than 370 meteorites known to have come from the Moon, weighing a total of 489 pounds.

That’s impressive, but what if astronauts could bring the entire moon back to Earth?

Not that Moon. The other one.

On February 15^th, astronomers with the NASA-funded Catalina Sky Survey at the University of Arizona announced the discovery of a new moon orbiting Earth. Kacper Wierzchos, one of the astronomers who made the discovery, posted several images of the object, designated 2020 CD3. Analysis of its orbit indicated that Earth’s gravity captured it three years ago when it was a small asteroid orbiting the sun. It’s tiny, only 6 to 12 feet in diameter. While it is too small to see without a large telescope, it is also small enough to be captured in a ship and returned to Earth. It is a captured asteroid and studying its makeup goes a long way to helping us better understand the origin of our solar system.

2020 CD3 Image credit: Kacper Wierzchos, Catalina Sky Survey, NASA

Wierzchos said of the discovery “It's a big deal, as out of approximately one million known asteroids, this is just the second asteroid known to orbit Earth (after 2006 RH120, which was also discovered by the Catalina Sky Survey).”

2006 RH120 eventually left Earth orbit after only nine months due to gravitational tugs and radiation pressure from the sun. 2020 CD3 will likely also leave Earth orbit eventually, but there is currently no evidence that solar radiation pressure is affecting its orbit. And it has already been a second moon for three years. So perhaps it will stick around for a while.

The Catalina Sky Survey’s mission is to hunt for and catalog all near-Earth asteroids that may pose an impact risk to Earth. While 2020 CD3 would not be a significant risk to Earth on impact, due to its small size, discovering that it is now Earth’s second moon may be even more exciting.

Each month, I write an astronomy-related column piece for the Oklahoman newspaper. After it is published there, I post that same column to my blog page.

This is reprinted by permission from the Oklahoman and www.newsok.com.