Last week, the BepiColombo spacecraft flew past Mercury for the fifth time, showing the planet in mid-infrared light for the first time. The images showed details of the temperature and composition of the planet closest to the Sun.
BepiColombo was launched in October 2018 and is scheduled to arrive at Mercury in November 2026, about a year later than originally planned. In early September, BepiColombo made its closest flyby of Mercury and its fourth gravitational acceleration, and now, during its fifth flyby of the planet, the spacecraft has received new data on the planet, which is hot during the day and cold at night.
The spacecraft collected new data about Mercury using the Mercury Radiometer and Thermal Infrared Spectrometer, or MERTIS. The instrument has captured details of Mercury in the mid-infrared wavelength range, in which details of the planet’s surface temperature, roughness, and mineral constituents become apparent.
“After almost two decades of development, laboratory measurements of hot rocks similar to those found on Mercury, and countless tests of the entire sequence of events during the mission, the first MERTIS data from Mercury are now available,” said Jörn Helbert, who helped develop the instrument as a co-investigator at the German Aerospace Center, in an ESA press release. “This is fantastic!”
The images show Basho Crater, an impact crater previously observed by the Mariner 10 and Messenger missions. In visible light, the crater stands out as a relatively pronounced spot on the planet’s surface. It is also visible in the mid-infrared.
“The moment we first looked at the MERTIS flyby data and were able to immediately distinguish the impact craters was breathtaking,” said Solmaz Adeli, a researcher at the Institute for Planetary Research at the German Aerospace Center, in the same release. “There’s so much new in this dataset – we’re going to see surface features that have never been observed in this way before.”
“We have never been so close to understanding the global mineralogy of Mercury’s surface with MERTIS ready for BepiColombo’s orbital phase,” Adeli added.
MERTIS data indicate that the Mercury surface had a temperature of 788° Fahrenheit (420° Celsius) during the flyby. Testing different minerals in the laboratory and observing how they glow in the mid-infrared can indicate the exact chemical cocktail present in the sediments on the planet’s surface.
Although BepiColombo’s arrival in Mercury’s orbit has been delayed, recent observations provide an up-close look at the planet, which scientists will be able to see in two years.
