German planetary researchers have created the most reliable map of silica (SiO2) to date using a new laboratory calibration. Concentrations across the surface of Earth’s moon and the first estimates of silica for Mercury. Their work is built around the Christiansen feature (CF), a mid-infrared spectral feature that changes predictably depending on the silica content of the material.
This colorful view of Mercury was created using images from MESSENGER’s color base map imaging campaign during its primary mission. These colors are not what Mercury looks like to the human eye; rather, the colors highlight chemical, mineralogical, and physical differences between the rocks that make up the planet’s surface. Image credit: NASA / Johns Hopkins University Applied Physics Laboratory / Carnegie Institution of Washington.
“Silica concentrations in planetary surface materials are a fundamental geochemical indicator used to infer the nature and evolution of planetary crusts,” said researcher Dr. Christian Lengli of the Max Planck Institute for Solar System Research and colleagues.
“It is a primary measure of rock composition and lithofacies definition, correlates with major mineral assemblages, and serves as a proxy for mineralogy and degree of magmatic differentiation.”
“However, determining silica concentrations on the Moon and Mercury using remote sensing observations has proven difficult.”
For the new study, the researchers synthesized seven types of glass spanning an extreme composition range from 0.5% to 97.6% silica.
They then used these glasses to refine the mathematical relationship between CF location and silica abundance.
“Glass beads perform a similar function to a calibration weight on a scale,” says researcher Dr. Iris Weber from the University of Münster.
“We know exactly how much it weighs, so we can correctly interpret the balance on the scales.”
“Similarly, glass beads allow us to draw correct conclusions from their infrared properties.”
Applying this calibration to global data from NASA’s Lunar Reconnaissance Orbiter Diviner instrument, the scientists created a silica map and determined that the moon is divided into silica-poor basalt layers (on average less than 46%) and silica-rich highlands (about 51%).
Their approach detected unusually high concentrations of silica (up to 76%) in unusual volcanic features such as Gruithuizen Dome, Hansteen Alpha, and the Russell Massif. These sites have long been suspected of being similar to rhyolite domes on Earth, but this has never been accurately quantified from orbit.
The authors validated their results against soil and rock samples from the Apollo, Luna, and Chang’e missions and found strong overall agreement.
According to the research team, the usefulness of this calibration extends beyond the moon.
Applying that to decades-old Earth-based infrared measurements of Mercury, the researchers estimate that Mercury’s innermost surface contains only about 37% silica, significantly lower than previous estimates derived from MESSENGER spacecraft data.
This discovery suggests that some of Mercury’s silicon may exist in the form of unusual metals or carbides, rather than typical silicate minerals.
“The moon is a kind of touchstone for us, an important conceptual stepping stone on our way to Mercury,” Dr. Lengli said.
“Our findings suggest that Mercury’s volcanic rocks formed from more deeply molten mantle material than previously thought.”
The team’s new method will be particularly valuable once the EU-Japan BepiColombo mission’s MERTIS instrument begins detailed observations of Mercury after it enters the science phase in 2027, and could also help characterize the surfaces of rocky exoplanets observed by NASA/ESA/CSA’s James Webb Space Telescope.
“We now hope to use data from ESA’s BepiColombo mission to confirm that Mercury’s surface has a low silicon dioxide content,” the scientists said.
“In November of this year, a probe consisting of two separable probes, each provided by ESA and JAXA, will enter orbit around this small planet.”
of result Featured in this month’s magazine planetary research.
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Christian Lenggly others. 2026.SiO2 There are many on the surfaces of the Moon and Mercury. planetary research 1(1);doi: 10.53480/bf74-m226
Source: www.sci.news
