The largest impact basins on the Moon in the visible side (left) and hidden (right). Credit: National Institute of Advanced Industrial Science and Technology.
The largest dark spot the moon, known as the Ocean of Storms ("Oceanus Procellarum"), has about 3,000 kilometers in diameter and can be a huge scar cosmic impact, researchers say.
The visible side of the Moon is somewhat different from the dark side. The vast plains of volcanic rock called "seas" cover almost a third of the visible side, but the dark side has only a few seas.
Researchers have proposed several explanations for the wide disparity between visible and hidden side of the moon, but now a team of scientists from Japan says that a huge collision may explain the dual nature of the Moon.
The researchers analyzed the composition of the lunar surface using data from Japanese lunar orbiter Kaguya / Selene. These data revealed that a variety of low-calcium pyroxene mineral concentrates around the Ocean of Storms and large impact craters as Aitken and Imbrium basins. This type of pyroxene is related to the merger and excavating lunar mantle material, and suggests that the Ocean of Storms corresponds to the remains of a cataclysmic impact.
This collision would have created "a sea of magma than 3,000 kilometers across several hundred kilometers deep," said lead study author Ryosuke Nakamura, planetary scientist at the National Institute of Advanced Industrial Science and Technology in Tsukuba, Japan.
Researchers say that collisions large enough to create the Ocean of Storms and other giant impact basins on the Moon would have left completely uncovered the original crust on the near side of the Moon. The bark that later formed there from molten rock product of these impacts would be very different from the dark side, explaining why its halves are so different.
The discovery provides the first evidence that the basin consists Procellarum was the remnant of a giant impact that could be confirmed by future missions lunar sample return, such as Moonrise, a proposed NASA mission to send an unmanned probe to collect moondust and return to Earth.
"Earth's neighbor probably experienced similar magnitudes impacts in the same period," said Nakamura. "This would have had a great effect on the onset of the formation of the continental crust of the Earth and the beginning of life."