Mercury Still Volcanically Active, NASA Spacecraft Finds

A NASA spacecraft has found evidence that the planet Mercury is still tectonically active.

NASA's MESSENGER (MErcury Surface, Space ENvironment, GEochemistry and Ranging) spacecraft captured images of steep cliffs called scarps on the surface of Mercury about 10 kilometers long, which resemble breaks in the planet's crust. Similar scarps could also be found on the planet, but all appear larger and more eroded and had been present since over 3.5 billion years ago, Science News reports.

However, the newly discovered scarps are different. According to Thomas Watters from the Smithsonian Institute in Washington, the cliffs were about less than 50 million years old, owing to their smaller sizes, sharp edges and lack of overlapping craters. The discovery, which was detailed in a paper published in Nature Geoscience, suggests that the planet's surface still fractures as it cools down and that some of the faults are active at present.

The images were captured by the MESSENGER spacecraft during the final 18 months of its mission when it flew closer to the surface of Mercury. The probe started to orbit Mercury in 2011 and ended with an intentional crash landing in April 2015.

Previous studies indicated that Mercury is gradually cooling despite its proximity to the sun. This cooling down causes the quakes and contractions on the planet. However, it is not clear whether these newly discovered scarps are related to the quakes.

An earlier study published in the Geophysical Research Letters suggested that Mercury ceased to be volcanically active about 3.5 billion years ago and that the planet has stopped evolving altogether. According to the study author Paul Byrne, Mercury has a smaller mantle and so it lost its heat much earlier than Venus, Mars, and Earth.

A close inspection of the planet will provide more information about its evolution and volcanic activity. The European-Japanese BepiColombo spacecraft, which is the second mission to Mercury, is slated to launch in 2018 and will arrive on the planet in 2024. It will have the same altitude as the MESSENGER but it will probe Mercury's southern hemisphere and allow scientists to get a better view of the planet's faults.