(CN) – Massive basins formed billions of years ago on Earth’s moon were assumed to be static geological formations, but a NASA study of the lunar bowls has found that they hold clues that the moon is actively transforming.
The moon, which does not have tectonic plates, only experiences tectonic action as it slowly loses heat from when it was formed nearly 4.5 billion years ago. The loss of heat over millions of years is causing its interior to shrink, wrinkling the surface and creating distinctive ridge lines and basins.
Previous studies have estimated that the moon’s basins all stopped contracting around 1.2 billion years ago and that geologic activity faded before dinosaurs roamed Earth.
However, a recent NASA study found that the surface is still being shaped by geological activity.
The study was led by Nathan Williams, a researcher at NASA’s Jet Propulsion Laboratory in Pasadena, California, and published March 7 in the scientific journal Icarus. It analyzed more than 12,000 images of lunar basins – called mares – taken by NASA’s Lunar Reconnaissance Orbiter Camera.
In at least one basin, the spacecraft found “wrinkle ridges,” which are curved hills and shallow trenches created by surface contraction as the moon loses heat and shrinks.
“The moon is still quaking and shaking from its own internal processes,” Williams said in a statement Monday. “It’s been losing heat over billions of years, shrinking and becoming denser.”
Researchers compared the effect to a car tire in winter that becomes denser and loses its hard surface as the temperature drops and the air inside the tire contracts.
Previous studies have found similar surface formations in the moon’s highlands, but wrinkle ridges have never been seen in basins before now.
Williams and his co-authors focused their analysis on images taken in a region near the moon’s north pole called Mare Frigoris, or the Cold Sea.
Researchers said in the study that as the ground under Mare Frigoris has shifted, massive ridges have formed, snaking along the ground for several miles. The longest ridge stretches for 250 miles – longer than the distance between New York City and Washington, D.C. – and rises as much as 1,000 feet.
Researchers estimate that some of the ridges were formed in the last billion years, while others “may be no older” than 40 million years old.
NASA says it can estimate how old a ridge is by examining the amount of debris flung up by meteors hitting the surface and covering nearby terrain, altering the landscape in a process called “impact gardening.”
Craters collect more debris the longer they are around, and craters smaller than the size of a football field would typically fill to the brim in under a billion years, according to scientists.
Williams examined images of ridges inside small, unfilled craters, which led him to deduce that the ridges emerged within the past billion years.
Researchers said they hope to glean more information about Earth and its moon by examining lunar geological activity such as moonquakes, which NASA instruments first recorded in 1969.
In April, a spacecraft designed to probe the depths of Mars’ surface as part of a study of the origins of the universe recorded the first Martian quake ever detected.