NASA Research Reveals That Mercury is Active

Mercury is Active After All

It’s small, it’s hot, and it’s shrinking. Surprising new NASA-funded research suggests that Mercury is contracting even today, joining Earth as a tectonically active planet. Credit: NASA/JHUAPL/Carnegie Institution of Washington/USGS/Arizona State University

New research suggests that Mercury is contracting even today, joining Earth as a tectonically active planet.

Images obtained by NASA’s MErcury Surface, Space ENvironment, GEochemistry, and Ranging (MESSENGER) spacecraft reveal previously undetected small fault scarps— cliff-like landforms that resemble stair steps. These scarps are small enough that scientists believe they must be geologically young, which means Mercury is still contracting and that Earth is not the only tectonically active planet in our solar system, as previously thought.

The findings will be reported in a paper in the October issue of Nature Geoscience.

“The young age of the small scarps means that Mercury joins Earth as a tectonically active planet, with new faults likely forming today as Mercury’s interior continues to cool and the planet contracts,” said lead author Tom Watters, Smithsonian senior scientist at the National Air and Space Museum in Washington, D.C.

Large fault scarps on Mercury were first discovered in the flybys of Mariner 10 in the mid-1970s and confirmed by MESSENGER, which found the planet closest to the sun was shrinking. The large scarps were formed as Mercury’s interior cooled, causing the planet to contract and the crust to break and thrust upward along faults making cliffs up to hundreds of miles long and some more than a mile (over one-and-a-half kilometers) high.

Shrinking Mercury is Active After All

Small graben, or narrow linear troughs, have been found associated with small fault scarps (lower white arrows) on Mercury, and on Earth’s moon. The small troughs, only tens of meters wide (inset box and upper white arrows), likely resulted from the bending of the crust as it was uplifted, and must be very young to survive continuous meteoroid bombardment.

In the last 18 months of the MESSENGER mission, the spacecraft’s altitude was lowered, which allowed the surface of Mercury to be seen at much higher resolution. These low-altitude images revealed small fault scarps that are orders of magnitude smaller than the larger scarps. The small scarps had to be very young, investigators say, to survive the steady bombardment of meteoroids and comets. They are comparable in scale to small, young lunar scarps that are evidence Earth’s moon is also shrinking.

This active faulting is consistent with the recent finding that Mercury’s global magnetic field has existed for billions of years and with the slow cooling of Mercury’s still hot outer core. It’s likely that the smallest of the terrestrial planets also experiences Mercury-quakes—something that may one day be confirmed by seismometers.

“This is why we explore,” said NASA Planetary Science Director Jim Green at Headquarters in Washington, D.C. “For years, scientists believed that Mercury’s tectonic activity was in the distant past. It’s exciting to consider that this small planet – not much larger than Earth’s moon – is active even today.”

1 Comment on "NASA Research Reveals That Mercury is Active"

  1. Madanagopal.V.C. | October 2, 2016 at 12:47 am | Reply

    Mercury is still very hot and it is no doubt that tectonic activity should be more vigorous here rather than our cold Earth. Moreover tectonic plate movements are common in all the spherical planets since its core should be very hot and this is the reason why they blow into a sphere just like blowing a glass bulb in the factory. Thank You.

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