Wrinkles on the moon could reveal secrets regarding devastating impacts that also ravaged Earth and other planets in their early days.
These impacts could have scoured life from the young Earth — but they might have also planted the ingredients for life as well, scientists said today at a European conference.
The researchers focused on giant basins on the moon believed to be wounds from the "lunar cataclysm," a time 3.8 billion to 4.2 billion years ago when the moon suffered heavy bombardment from asteroids or comets. There are roughly 50 recognizable lunar basins more than 186 miles (300 kilometers) wide, most of which are thought to date from then.
To learn more about these basins, the researchers peered at pictures taken by a microcamera on SMART-1, a European Space Agency satellite that orbited the moon from 2004 to 2006. They combined data from these images with records from the U.S. Clementine space probe, which looked at visible, ultraviolet and infrared light from the moon during 1994 and measured its gravitational field to determine the makeup and concentration of minerals in the lunar surface.
Researchers examined the circular Humorum basin. Clementine suggested it had a concentration of mass within a small area, a hint that a massive impact pounded the surface there long ago.
SMART-1 revealed wrinkles in the basin suggesting it was in fact caused by an impact. These include concentric "graben," or elongated, trench-like features around the basin's edge, which are formed due to the presence of a mass concentration. "When you put some mass on your own skin, you can see wrinkles pop up, and this is what we see with the Humorum," SMART-1 principal scientist Bernard Foing told Space.com.
The researchers had searched for another hint of an impact, known as radial stress faults-cracks that would have radiated out like spokes in a wheel. However, the impact on the Humorum's thin crust apparently led to massive lava flows that flooded the basin and obliterated these cracks. Still, Foing and his colleagues did find other signs of an impact-strike-slip faults, where the ruptures are vertical and one side slides past the other.
"It is now possible to study fine, small-scale geological features that went undetected earlier," Foing said.
The researchers also looked at the Procellarum basin. Clementine showed it had no sign of mass concentration, and the SMART-1 images confirmed it did not have any wrinkles suggesting an origin from an impact. Instead, it may have formed due to tectonic activity 3.84 billion years ago.
Foing added the cataclysm that pounded the moon also likely ravaged Earth and the rest of the inner solar system. "That was about the same time life is thought to have originated on Earth," he said. "Those are odd conditions for life to emerge. Maybe life managed to endure those challenges, or maybe those asteroids or comets brought some of the ingredients of life with them, such as water, or carbon, or organics."
Foing and his colleagues detailed their findings at the European Planetary Science Congress.