In an astonishing new reveal, the BepiColombo spacecraft has captured Mercury in an unprecedented light—specifically, mid-infrared wavelengths. This remarkable achievement occurred during its fifth flyby of the innermost planet of our solar system on December 1st, marking a significant milestone in our understanding of Mercury.

Flying past Mercury at a distance of approximately 37,626 kilometers (about 23,400 miles), this flyby allowed scientists to utilize the Mercury Radiometer and Thermal Infrared Spectrometer (MERTIS) for one of the first times to analyze the planet's northern hemisphere. Mid-infrared light, invisible to the naked eye, is crucial for providing insight into the temperature and mineral composition of Mercury's scorching surface.

This December flyby was not the closest encounter BepiColombo has had with Mercury; that honor belongs to its September 4 pass, which skimmed only 165 kilometers (103 miles) above the planet's rugged terrain. As BepiColombo progresses toward its ultimate goal—settling into orbit around Mercury in late 2026—its upcoming encounters will reduce the distance to a mere 590 kilometers (370 miles) at closest approach.

Over the course of six planned flybys—two already completed, with the last scheduled for January 2025—BepiColombo is gathering vital data to refine its scientific objectives for its future orbital operations. One of the pivotal questions driving this research is understanding the unique geological evolution of Mercury, especially given its proximity to the sun's intense heat and gravitational forces.

MERTIS stands at the forefront of this investigation. It has been meticulously designed to analyze how different minerals emit mid-infrared radiation when heated. A dedicated team has spent nearly 20 years experimenting with various minerals, reaching temperatures exceeding 400 degrees Celsius (752 degrees Fahrenheit) in a laboratory setting, crafting a comprehensive database of these minerals' thermal profiles. This database is essential for making comparisons with the data collected from Mercury's surface, enabling scientists to identify material compositions and assess terrain features.

"Interestingly, we found that Mercury's surface shows a surprising deficiency in iron. This motivated us to explore synthetic and natural minerals known for their lack of iron," said Solmaz Adeli, project lead at the German Aerospace Center.

During this latest flyby, MERTIS imaged a vast area of Mercury, capturing intriguing features such as expansive volcanic plains and portions of the Caloris Basin—a massive impact crater's rocky plain. The images also featured the infamous Bashō Crater, which has been previously photographed by earlier missions, including Mariner 10 and Messenger.

Dr. Adeli expressed the exhilaration of analyzing the new data: "The moment we distinguished impact craters in the MERTIS flyby data was breathtaking! There is an entire dataset brimming with discoveries, revealing surface features that have never been seen before in such detail."

While MERTIS provided initial images with a resolution of 26 to 30 kilometers (16 to 19 miles), researchers eagerly await the finer details that will come once BepiColombo enters its planned orbit. At that stage, MERTIS will be capable of mapping Mercury's surface at a precision of 500 meters (547 yards), revealing a complete picture of its geological history.

In summary, BepiColombo's groundbreaking discoveries hold the potential to redefine our understanding of Mercury, offering insights that could change the narrative of how rocky planets form and evolve in our solar system. As the spacecraft approaches its ultimate mission, the universe holds its breath in anticipation of the insights yet to come.