Earth’s moon is hiding an enormous secret on its storied dark side. Deep below the moon’s South Pole-Aitken basin (the largest preserved impact crater anywhere in the solar system), researchers have detected a gargantuan “anomaly” of heavy metal lodged in the mantle that is apparently altering the moon’s gravitational field.
According to a study of the mysterious blob, published April 5 in the journal Geophysical Research Letters, the anomaly may be the heavy leftovers of the asteroid that crashed into the far side of the moon and created the giant South Pole-Aitken crater some 4 billion years ago. However, all that researchers can say for sure at this point is that the blob is big — likely weighing somewhere in the neighborhood of 2.4 quadrillion US tons (2.18 quintillion kilograms).
“Imagine taking a pile of metal five times larger than the Big Island of Hawaii and burying it underground,” lead study author Peter James, assistant professor of planetary geophysics at Baylor University’s College of Arts & Sciences, said in a statement. “That’s roughly how much unexpected mass we detected.”