Researchers find signs of recent tectonic activity on the moon

Tuesday, 21 February 2012 09:04

Human understanding has progressed a long way from seeing the moon as a deity traveling through the sky or a big wheel of cheese. But many of the details of the moon, from its formation to its current internal workings, remain a mystery to a large degree.

ArsTechnica reports that one new paper, however, finds evidence that could reshape perceptions of the moon. Led by Thomas Watters from the Smithsonian Institute in Washington, D.C., the group published recent findings in the journal Nature Geosicence drawing on data from the Lunar Reconnaissance Orbiter.

Designed as part of plans to develop a base on the moon, the LRO has been using a variety of new tools to make a detailed, three-dimensional map of the surface of the moon, placing a particular emphasis on potential safe landing points.

But the group led by Watters noted an entirely different feature in some of the early images being sent back from the satellite, in particular a series of ravines they believe are indicative to recent geological activity.

Space.com reports that these ravines, known as graben, are marked by the two cracks to their sides. Located in the darkened stretches of rock known as mare basalts, the scientists believe that they must indicate recent tectonic activity simply because they are largely unmarred by craters, as would be expected of any long-standing geological feature. Some of them even run cleanly through presumably pre-existing craters.

"We think they're less than 50 million years old, but they could be 10 million years old, could be 1 million years old, could have happened 40 years ago," Watters told Space.com. "The intriguing picture that's emerging of the moon is that there is recent geological activity going on."

Watters' group suggest that these findings could serve as evidence against the traditional conception of the moon's formation. Most scientists have imagined that moon resulted from a collision between the Earth and an object roughly the size of Mars, which launched a ball of molten rock into orbit around the planet. This ball then slowly cooled and contracted into the moon seen orbiting the Earth today.

But a contracting crust leads to wrinkles and cliffs. The graben found by the LRO should only be produced by the expansion of the lunar surface, cracks forming as the rock swells. This suggests that, while the moon is undoubtedly cooling overall, some parts of the crust may still be expanding.

This view is supported by information provided by the seismometers placed on the surface of the moon by the Apollo missions in the 1970s. Space.com reports that data show the moon retains a molten outer core, surrounded by a layer of partially melted material, active enough to cause more than 6,000 deep moonquakes over the eight years in which the seismometers were active.

"The moon may not only have been tectonically active recently, but may still be tectonically active today," Watters said.

If this is the case, it could support alternative ideas for the moon's creation, such as the theory that two smaller moons collided, leading to inconsistent heating of the moon's surface.

Space Daily reports that new evidence could help to explain the relative lack of volcanic activity as well. A group of researchers led by VU University Amsterdam's Mirjam van Kan Parker and Wim van Westrenen used intense X-rays to analyze the density of artificially created moon magma, using different samples of moon rocks.

The experiment found that a certain kind of magma, composed of certain titanium-rich rocks, formed a magma just as dense as the surrounding rocks, making it less likely to travel to the surface.