The asteroid that formed moon’s Imbrium Basin, one of the largest craters in the solar system, might have been bigger than previously calculated. Researchers from Brown University have evaluated geological features on the moon to make new calculus. The Imbrium Basin was created 3.8 billion years ago after a massive protoplanet-sized asteroid collided with the moon.

Researchers have proposed that the asteroid was ten times more massive than previously thought. Pete Schultz, a professor of planetary sciences at Brown University, stated that the moon could offer us clues to understand the entire solar system and what was happening 3.8 billion years ago. Detailed results of the geological investigation were published Thursday in the journal Nature.

 The Imbrium Basin has been an object of study since the 19th Century. Photo Courtesy of Robert Reeves
The Imbrium Basin has been an object of study since the 19th Century. Photo Courtesy of Robert Reeves

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

Researchers had previously calculated the size of the asteroid using computer models. New findings demonstrate that the rocky body was two times larger in diameter.

The study suggested that the early Solar System was full of asteroids with the same size as a protoplanet. Researchers have also analyzed impact basins on Mars and Mercury, using the Vertical Gun Range at the NASA Ames Research Center.

Study details and other theories: geological features of the moon can tell us a lot

The Imbrium Basin is 750 miles in diameter and is located in the northwestern quadrant of the Moon’s face, wrote the authors of the study. Massive grooves and gashes that can be seen from earth surround the crater. All these features formed the Imbrium Sculpture.

Researchers have also found a second group of holes, which was apparently formed by pieces of the asteroid that impacted the moon. These grooves provided data to calculate the estimated size of “the impactor.”

NASA’s Vertical Gun Range is powerful enough to fire small projectiles at up to 16,000 miles per hour, said Brown University in a press release. The technology is equipped with high-end cameras that register the dynamics of the ballistics. The same cameras are capable of recording objects that travel up to one million frames per second. As a result, the team was able to study the pattern of debris, Prof Schultz told the BBC’s Science Program.

Schultz, who is also a professor of earth and environmental sciences, conducted experiments with low-angle impacts. He, alongside David Crawford of the Sandia National Laboratories built a new computer model that took into account the evaluated geological features. Professor Schultz could later determine the size of the impactor, after analyzing the trajectory of chunks that it released. Final estimations suggested that the celestial body had a diameter of 150 miles. That size is enough to classify the impactor as a protoplanet.

During this period, the moon was closer to the Earth that today.The asteroid could have had 186 miles across, although Professor Schultz preferred to suggest a “low-end estimate.” He told the BBC that the object was traveling at a speed of up to 40,000mph at the time it collided with the moon, at an angle of 30 degrees.

Shultz: lost giants might have formed large basins on the Moon

The team from Brown University has suggested that early impactors spread all around the old surface of the moon. This material merged with the soil and rock. The new theory could explain why samples obtained by the Apollo explorers had elevated levels of meteoritic content.

The Apollo 16 mission “landed downrange from the Imbrium impact”, wrote researchers. Chunks from these lost giants that collided with the moon could have been part of the Late Heavy Bombardment, which took place 3.8 billion years ago.  The Late Heavy Bombardment is a period in which thousands of craters were formed on the Moon and Mercury. Celestials bodies that impacted the moon could have broken in the Moon and later escaped to other places in the Solar System as a result of gravity.

Chunks of asteroids would have traveled around the orbits of the Earth and the moon, creating huge craters of up to 12.4 miles of diameter. Authors said that space investigation involving the moon is “fantastic,” because the natural satellite can provide extensive information about the Solar System.

“These chips off the old blocks could have contributed significantly to the impact record we see on the Moon and other terrestrial planets. The scarred face of the moon can tell us quite a lot about what was happening in our neighborhood 3.8 billion years ago,” concluded Professor Schultz.

Source: Brown University Press Release