Mercury's surface holds far less silicon dioxide than thought

Overview

Updated 6 hours ago

Mercury's surface holds about 37 percent silicon dioxide by mass, up to 25 percent less than earlier estimates. That gap points to a hotter volcanic past, with lava rising from deeper mantle regions melted at extreme temperatures.

No lander has touched Mercury and no sample has ever been returned, so every claim about its surface comes from remote sensing. BepiColombo, a joint European Space Agency and Japan Aerospace Exploration Agency mission, enters Mercury orbit in November and carries an infrared instrument built to measure this exact quantity.

Why it matters

If confirmed, Mercury's deep, hot melting rewrites models of how the innermost planet's crust formed and how differently it evolved from Earth.

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Key Indicators

37%

Silicon dioxide on Mercury's surface (by mass)

New lab-calibrated infrared estimate, down from the 49–60% range based on MESSENGER data.

25%

Maximum reduction from previous estimates

The gap between 37% and the low end of the old 49–60% range.

8.5 µm

Christiansen Feature wavelength used for estimate

Infrared spectral feature that directly constrains silicon dioxide content.

Nov 2026

BepiColombo Mercury orbital insertion

Scheduled for November 21, 2026, with full science operations from April 2027.

4.1–3.5 bya

Mercury's volcanic era

Lava plains and explosive vents formed during this window, per MESSENGER findings.

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People Involved

Christian Renggli

Lead author of the Planetary Research study; head of the Experimental Laboratory Magma Ocean research group at the Max Planck Institute for Solar System Research

Leading follow-up work ahead of BepiColombo's arrival

Organizations Involved

Max Planck Institute for Solar System Research

Research Institute

Led the new silica study; home of the Experimental Laboratory Magma Ocean group

German planetary science institute that led the new Mercury surface composition study with the Universities of Münster and Göttingen.

BepiColombo (ESA/JAXA joint mission)

Space Mission

Approaching Mercury; orbit insertion scheduled November 21, 2026

Two-probe ESA/JAXA mission on an eight-year cruise; its MERTIS infrared instrument will test the new low-silica estimate.

NASA MESSENGER mission

Space Mission

Completed 2015; its data underpin the older silica estimates now being questioned

First spacecraft to orbit Mercury (2011–2015); its elemental ratio data produced the 49–60% silica estimates now being revised.

MERTIS instrument team (DLR / University of Münster)

Instrument Development Team

Will collect the confirming measurements from April 2027

Built the Mercury Radiometer and Thermal Infrared Spectrometer that will test the new silica estimate at high resolution.

Timeline

March 2011 April 2027

8 events Latest: Today

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April 2027
MERTIS full science operations begin
Upcoming Mission Milestone

MERTIS infrared instrument maps Mercury's mineralogy, covering the Christiansen Feature used in the new calibration.
April 1st, 2027
November 2026
BepiColombo scheduled to enter Mercury orbit
Upcoming Mission Milestone

Orbital insertion date; full science operations follow in April 2027.
November 21st, 2026
September 2026
Low-silica finding gains wide attention
Today Discovery

News of the hot volcanic past spreads as the study reaches broad audiences.
Today
BepiColombo probes separate from transfer module
Mission Milestone

Both science probes detach from the transport module, starting the final approach phase.
September 3rd, 2026
August 2026
New silica study published
Discovery

Planetary Research journal reports 37% silicon dioxide on Mercury's surface, up to 25% below older estimates.
August 1st, 2026
October 2018
BepiColombo launches
Mission Milestone

Joint ESA/JAXA mission lifts off from Kourou, French Guiana, on an eight-year cruise.
October 20th, 2018
April 2015
MESSENGER mission ends
Mission Milestone

Spacecraft impacts Mercury's surface after four years of orbital observations.
April 30th, 2015
March 2011
MESSENGER enters Mercury orbit
Mission Milestone

First spacecraft to orbit Mercury; begins mapping surface composition from elemental ratios.
March 18th, 2011

Scenarios

BepiColombo Confirms Mercury's Low-Silica Crust

Likely Resolves by End of 2027

Discussed by: Christian Renggli and the Max Planck research team; the study authors expect MERTIS to verify the low value

MERTIS begins full operations in April 2027 and maps the Christiansen Feature across Mercury's surface. If its measurements show silica near 37 percent by mass, the deep-melting model solidifies. The crust would record mantle material melted at greater depths and higher temperatures than Earth's volcanic rocks.

MERTIS Revises Silica Estimate Back Upward

Possible Resolves by End of 2027

Discussed by: Planetary scientists noting the new infrared calibration method is untested at Mercury's high surface temperatures

If MERTIS data show silica well above 37%, closer to the MESSENGER-era 49–60% range, the infrared calibration method may need adjustment for Mercury's surface conditions. The lab experiments used to calibrate the method might not fully replicate the planet's thermal environment, pushing the estimate off.

Oxygen-Loss Theory Gains Ground on Mercury's Low Silica

Possible Resolves by Q2 2028

Discussed by: The study authors, who note Mercury could have gradually lost oxygen over billions of years

Rather than deep mantle melting alone, the low silica could reflect oxygen escaping from Mercury's surface over time. Follow-up studies tracking surface chemistry, atmospheric escape, or isotopic ratios could separate the two mechanisms. If the oxygen-loss path gains support, the story shifts from 'hotter interior' to 'leaky planet.'

Historical Context

3 moments from history that rhyme with this story — and how they unfolded.

July 1969 – December 1972

Apollo lunar samples recalibrate remote sensing (1969–1972)

Before Apollo returned Moon rocks, telescopic and early orbital remote sensing gave rough estimates of lunar surface composition. Apollo samples provided direct measurements that differed substantially from predictions in key elements, forcing recalibration of every remote-sensing technique used to study the Moon.

Then

Lunar remote sensing got anchored to real samples; calibration curves were redrawn.

Now

Established the principle that remote sensing needs independent calibration. For bodies without samples, calibration must come from laboratory experiments and cross-checking instruments.

Why this matters now

Mercury has never had a rock sample returned. The new infrared calibration, tested in the lab, is the closest scientists can get to a ground-truth anchor for an unreachable surface.

August 1990 – October 1994

Magellan's radar mapping overturns Venus assumptions (1990–1994)

NASA's Magellan spacecraft mapped 98 percent of Venus with synthetic aperture radar, revealing a volcanic surface completely unlike the picture built from Earth-based radar and earlier flybys. It showed young resurfacing, vast volcanic plains, and shield volcanoes.

Then

Overturned prior understanding of Venus's geology, showing a planet resurfaced by volcanism.

Now

Demonstrated that orbital instruments can drastically revise surface understanding built from less direct methods.

Why this matters now

Like Magellan at Venus, BepiColombo's direct instruments may substantially revise the MESSENGER-era estimates for Mercury — in either direction.

March 2011 – April 2015

MESSENGER reshapes Mercury's story (2011–2015)

MESSENGER was the first spacecraft to orbit Mercury, after Mariner 10's 1970s flybys. Its instruments measured elemental abundances that scientists used to estimate surface silica at 49–60 percent. It also revealed lava plains over a kilometer thick, pyroclastic vents, and explosive volcanic features called hollows.

Then

Produced the most detailed view of Mercury's surface chemistry ever, replacing decades of flyby-era guesses.

Now

Its elemental-ratio estimates became the standard reference for Mercury's composition. Those estimates are now being challenged by the new infrared work.

Why this matters now

The old silica numbers came from MESSENGER's elemental-ratio method. BepiColombo's MERTIS uses a different, direct infrared approach, providing an independent check of a decade-old estimate.