Mercury Volcanic Activity 3.5 Billion Years Ago Shows Outcome When Rocky Planets Contract, Cool

First Posted: Aug 11, 2016 06:44 AM EDT

Mercury's volcanic activity is suggested to have ended about 3.5 billion years ago according to a paper published at the Geophysical research Letters journal. Scientists believe that these findings could lead them to geological evolution and discover what happens when rocky planets contract and cool.

The team, with planetary geologist and NC State assistant professor, Paul Byrne, explains that volcanic activity on rocky planets come in two types, explosive and effusive. The explosive volcanic activity is a violent event while the effusive volcanism refers to a widespread lava flow that slowly pours out over a landscape. The team believes that the effusive volcanic activity is the key process in the crust formation of rocky planets such as Mercury, Nature World News reported.

Determining the ages of effusive volcanic deposits could lead scientists to a planet's geological history, NC State News reported. Records claims that effusive volcanism was active a few hundred million years ago on Venus while it stopped a few million years ago on Mars and still takes place on Earth today. However, the duration of effusive volcanic activity on Mercury had not been known until today.

Scientists were able to determine when the effusive volcanic activity stopped on Mercury using the data gathered from the NASA Messenger mission. Scientists do not have physical samples from the planet that could be used for radiometric dating so they made use of Mercury's surface images. They used the crater size-frequency analysis wherein the craters' numbers and sizes are plotted into established mathematical models. This allowed them to calculate the ages of effusive volcanic deposits on the planet.

Mercury's deposit analysis resulted to a conclusion that the major volcanic activity stopped billion years ago, which is also the earliest in the inner solar system. Byrne says that the smallest planet in the solar system has a smaller mantle. The radioactive decay of the mantle produces heat compared to its neighbors. Since Mercury began to contract, its crust sealed off any conduits that magma could use to reach the surface.

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