About 800 million years ago, a flurry of little ones asteroids it strucked with Moon, hitting the lunar surface with groups of craters. But the moon was not the only victim of this cosmic bombardment.
If the moon experienced multiple asteroid strikes during this time, its close neighbor and parent planet – land – it was probably also marked by the same cosmic “storm”, even if time has long since erased all traces of those ancient impacts. And that massive bombardment may have turned Earth into a giant snowball, the researchers reported in a new study.
Judging by the size and number of lunar craters, that asteroid storm would have been substantial. Scientists estimated that the collective weight of the asteroids that hit Earth and the Moon may have been up to 60 times the mass of the asteroid that crashed into what is now Mexico and formed the Chicxulub crater, ending the reign of the dinosaurs.
Related: 5 weird and cool things we’ve recently learned about the moon
Even when viewed from Earth without much magnification, the moon’s face is clouded by thousands of craters, created by the space rocks that buzzed at first Solar system. By studying the size and grouping of impact craters on different parts of the lunar surface, scientists can approximate the ages of these scars, a technique known as “crater chronology,” lead author of the study, Kentaro Terada, professor at Department of Earth and Space. Science at Osaka University in Japan, he told Live Science in an email.
For the new study, Terada and his co-authors analyzed lunar data collected by the Selenological and Engineering Explorer mission of the Japanese space agency (SELENE), launched in 2007. (This probe quickly became known as “Kaguya” after Kaguya-hime, a moon princess in a popular Japanese folk tale, sister site of Live Science Space.com reported that year).
Kaguya mapped the enigmatic far side of the moon – the hemisphere that always moves away from Earth and is sometimes mistakenly called the “dark side” even though it receives sunlight – and on February 10, 2009, Kaguya captured an impressive film of Earth outshining the sun, the first view of the moon of such an event. Upon completing her mission, Kaguya was sent to the moon in a controlled crash on June 10, 2009, Space.com reported.
Scientists suspected that Kaguya’s observations of lunar craters could reveal a great deal about ancient impacts on Earth. Craters on the moon do not erode as they do on Earth; while asteroid impacts on Earth that are more than 600 million years old resist nothing by Volcanic activity and erosion, very old impacts on the moon remain well preserved, Terada said in the email.
Counting craters
Using Kaguya’s data, the researchers investigated 59 large lunar craters ranging from 12 to 58 miles (20 to 93 kilometers) in diameter. Then, on ejection of the large craters, the circle of surrounding material ejected by the impact, the study authors counted the number of smaller craters measuring from 300 feet (0.1 km) to 0.6 miles (1 km) in diameter. Scientists approximate the age of surfaces in the solar system by calculating the density of their craters.
The Apollo 11 mission previously collected soil samples from one of those large craters, Copernicus, which dates back some 800 million years. And eight of the large craters had a similar number of smaller craters in their ejection, hinting that they formed at the same time, likely as a result of an asteroid shower, Terada explained.
Because Earth and the moon have coexisted as cosmic partners for approximately 4.5 billion years, “this new finding provides us with a crucial insight into the Earth-Moon system,” the scientists wrote in the study. “Asteroid rains must have occurred not only on the moon but also on Earth,” they said.
Because the moon maintains an almost pristine record of these ancient impacts, scientists can look at the moon as “a witness to the history of the solar system,” shedding light on Earth’s missing impact history, Terada said.
Based on the orbits of known asteroid groups about 800 million years ago, scientists suspected that the storm was caused by a disruption of Eulalia, a rocky, carbon-rich body in the asteroid belt of our solar system, measuring approximately 40 kilometers (25 miles). in diameter. When scientists modeled the size and number of projectiles that crashed into the moon and Earth, they calculated that the mass of space debris would have totaled millions of billions of kilograms, according to the study.
This offers an intriguing new perspective on dramatic climate change in Earth’s distant past that appeared between 800 and 700 million years ago, the authors wrote.
During this glacial period, known as “Snowball Earth, “the planet suffered a deep global freeze, its entire surface covered in ice from pole to pole. Scientists suspected that volcanoes or other” Earth works “caused a great cooling, but this new lunar evidence suggests that the trigger it may have originated in space, and the so-called Snowball Earth may have resulted from an asteroid bombardment.
“The chronology of the lunar crater provides a new insight into the external forcing of asteroids that could have fueled global environmental change,” Terada said.
The findings were published online July 21 in the journal. Nature.
Originally published in Live Science.
