An asteroid, even possibly a protoplanet, as long as the state of New Jersey struck Earth’s moon some 3.8 billion years ago, and helped to create the features most people recognize as the right eye of the “man in the moon,” according to an article on eurekalert.org.

Brown University Earth, Environmental and Planetary Sciences professor Pete Schultz, said in a paper published in the journal Nature, the collision caused the formation of the Imbrium crater, one of the moon’s most recognizable markings.

“We show that Imbrium was likely formed by an absolutely enormous object, large enough to be classified as a protoplanet,” said Schultz.  “This is the first estimate for the Imbrium impactor’s size that is based largely on the geological features we see on the Moon.”

Schultz added the previous estimates of the size of the object that struck the moon were only about 50 miles in diameter, but the new research suggests the asteroid was likely three times that size.  The determination also helped to solve one of the mysteries that have long surrounded the Imbrium.

The crater itself is found on the northwestern quadrant of the moon, measuring about 750 miles across, and is visible from the Earth.  With even small telescopes, an amateur astronomer can see the grooves and gashes that surround the crater that were created as the rocks were expelled upon impact.  These features radiate from the center of the crater, similar to the spokes on a wheel, and are concentrated on the southeast side of the crater.

But a second set of grooves, appearing to come from a region to the northwest, have long puzzled astronomers.  Saying no one was quite sure of the origin of the the second set of grooves, Schultz conducted experiments with the Vertical Gun Range at NASA’s Ames Research Center to surmise the second set was caused by a part of the impacting object that sheared off, and continued on its way.  Schultz used the size of those grooves to determine the size of the impacting object.

The models that Schultz and colleague David Crawford of the Sandia National Laboratories generated revealed the physics that took place with such an impact.  These models also suggest the thousands of chunks that broke off and continued could account for a number of the impacts during the period known as the Late Heavy Bombardment, between 3.8 and 4.0 billion years ago.

Schultz added, “These chips off the old blocks could have contributed significantly to the impact record we see on the Moon and other terrestrial planets.”