While Earth's volcanoes have continued to fume throughout most of its history, volcanoes on Mercury have been shut down for billions of years. Though Mercury’s volcanoes have long since gone extinct, a few clues on its surface have shed light on what the planet may have been like back when it was volcanically active over 3.5 billion years ago.
One such clue is silicon dioxide, otherwise known as silica — on Earth, we know it as the primary component of sand. While astronomers don’t have silica samples from Mercury at the ready, they’ve still managed to determine the silica content of Mercury’s surface by using tiny lab-made glass beads, adding an unexpected twist to the origin of Mercury’s volcanic rocks, according to a study in Planetary Research.
“Our findings suggest that the volcanic rocks on Mercury formed from more deeply melted mantle material than previously assumed,” said study first author Christian Renggli, a planetologist at the Max Planck Institute for Solar System Research, in a statement.
How Mercury's Volcanoes Shut Down
While it isn’t yet fully understood how Mercury’s volcanoes shaped the planet’s appearance today, astronomers do know one crucial detail: Mercury has been gradually shrinking ever since it formed 4.5 billion years ago. This process, called “global contraction,” is driven by the constant cooling of Mercury's interior.
Explore All OptionsMercury is still contracting today, as indicated by young scarps on its surface. It’s believed that these cliffs formed relatively recently from the planet’s crust pushing together and thrusting upward, a result of global contraction, according to the Smithsonian Institution.
This gradual shrinking likely shut off surface volcanism on Mercury around 3.5 billion years ago, according to North Carolina State University. Our moon, which was also volcanically active in the distant past, went through a similar experience, its volcanoes becoming dormant because of contraction.
Read More: Volcanic Activity on Mars Could Help in the Search for Life on Other Planets
Calibrating with Glass Beads
The new study has taken a closer look at Mercury’s silica content to better understand the planet’s previous volcanic activity. But since no landers have touched down on Mercury, and therefore no rock samples have ever been collected, the researchers had to instead rely on an indirect approach to assess infrared radiation on Mercury, which can provide insight into the surface’s silica content.
To determine the silica content of Mercury's surface, the researchers created tiny glass beads — only about half a millimeter in size — with precisely defined proportions of silica and determined the exact properties of their infrared radiation.
“The glass beads serve a similar function to calibration weights on a scale,” said study author Iris Weber, a professor of geological planetology at the University of Münster, in the statement. “Their weight is known precisely. They therefore allow us to correctly interpret the scale’s balance. Similarly, the glass beads allow us to draw the correct conclusions from the properties of the infrared radiation.”
Lacking Silica on the Surface
Having used the glass beads as a sort of calibration, the researchers then tested the relationship between silica and infrared radiation on the moon; NASA’s Lunar Reconnaissance Orbiter has been measuring the moon’s infrared radiation since 2009. This data allowed the researchers to create the first complete map of silica content of the moon’s surface, which was verified through rock samples that have been brought back to Earth.
“The moon is a kind of touchstone for us — and an important conceptual stepping stone on our way to Mercury,” said Renggli.
These steps ultimately led researchers to use the same approach on Mercury, analyzing its infrared radiation to find that silica is up to 25 percent less abundant on Mercury's surface than previously thought. This further highlights the idea that Mercury’s volcanoes likely behaved differently than Earth’s comparatively silica-rich volcanoes.
The researchers expect the low silica content of Mercury's surface to be confirmed by BepiColombo, a mission jointly operated by the European Space Agency and the Japan Aerospace Exploration Agency. The spacecraft, which will enter orbit around Mercury in November 2026, could help open a new window into the planet's volcanic history with measurements of its surface.
Read More: Space Volcanoes Tell the Explosive History of Mars, Venus, and Multiple Moons
Article Sources
Our writers at Discovermagazine.com use peer-reviewed studies and high-quality sources for our articles, and our editors review for scientific accuracy and editorial standards. Review the sources used below for this article:
- This article references information from a study published in Planetary Research: The SiO2 abundance on the surfaces of the Moon and Mercury
- This article references information from the Smithsonian Institution: Mercury Joins Earth As Tectonically Active Planet
- This article references information from North Carolina State University: Mercury’s Volcanic Activity – or Lack of it – Could Help Us Find Other Earth-like Worlds
