The ESA/JAXA BepiColombo mission captured its first images of its destination planet Mercury as it swooped past in a close gravity assist flyby.
The closest approach occurred on October 1, 2021, at 23:34 UTC, at an altitude of 199 km above the planet’s surface. During the encounter, images from the spacecraft’s monitoring cameras were collected, as well as scientific data from a variety of instruments. The images were already downloaded on Saturday morning, and a selection of first impressions is presented here.
BepiColombo captured this view of Mercury on October 1, 2021, as the spacecraft flew past the planet for a gravity assist maneuver. The image was taken at 23:44:12 UTC by the Mercury Transfer Module’s Monitoring Camera 2, when the spacecraft was about 2418 km from Mercury. Credit: ESA/BepiColombo/MTM, CC BY-SA 3.0 IGO
“The flyby was flawless from the spacecraft point of view, and it’s incredible to finally see our target planet,” says Elsa Montagnon, Spacecraft Operations Manager for the mission.
The monitoring cameras take black-and-white snapshots with a resolution of 1024 x 1024 pixels and are positioned on the Mercury Transfer Module to capture the spacecraft’s structural elements, such as its antennas and magnetometer boom.
Images were taken starting about five minutes after the close approach and lasting up to four hours. Because BepiColombo arrived on the planet’s nightside, conditions were not ideal for taking images directly at the closest approach, so the closest image was captured from a distance of about 1000 kilometers away.
Several large impact craters can be seen in many of the images.
BepiColombo captured this view of Mercury on October 1, 2021, as the spacecraft flew past the planet for a gravity assist maneuver. This image was taken at 23:44:57 UTC by the Mercury Transfer Module’s Monitoring Camera 3, when the spacecraft was 2687 km from Mercury. Credit: ESA/BepiColombo/MTM, CC BY-SA 3.0 IGO
“It was an incredible feeling seeing these almost-live pictures of Mercury,” says Valetina Galluzzi, co-investigator of BepiColombo’s SIMBIO-SYS imaging system that will be used once in Mercury orbit. “It really made me happy meeting the planet I have been studying since the very first years of my research career, and I am eager to work on new Mercury images in the future.”
“It was very exciting to see BepiColombo’s first images of Mercury, and to work out what we were seeing,” says David Rothery of the UK’s Open University who leads ESA’s Mercury Surface and Composition Working Group. “It has made me even more enthusiastic to study the top quality science data that we should get when we are in orbit around Mercury, because this is a planet that we really do not yet fully understand.”
BepiColombo captured this view of Mercury on October 1, 2021, as the spacecraft flew past the planet for a gravity assist maneuver. The image was taken at 23:40:27 UTC by the Mercury Transfer Module’s Monitoring Camera 3, when the spacecraft was 1183 km from Mercury. Credit: ESA/BepiColombo/MTM, CC BY-SA 3.0 IGO
Although the cratered surface of Mercury appears to be similar to that of Earth’s Moon at first glance, Mercury has a very different history. BepiColombo’s two science orbiters – the ESA’s Mercury Planetary Orbiter and the JAXA’s Mercury Magnetospheric Orbiter – will study all aspects of the mysterious Mercury, from its core to surface processes, magnetic field, and exosphere, to better understand the origin and evolution of a planet close to its parent star. For example, it will map Mercury’s surface and analyze its composition to learn more about the planet’s formation. According to one theory, it began as a larger body that was then stripped of most of its rock by a massive impact. This left the Planet with a relatively large iron core, where its magnetic field is generated, and only a thin rocky outer shell.
Mercury has no equivalent to the ancient bright lunar highlands: its surface is dark almost everywhere and was formed billions of years ago by massive outpourings of lava. These lava flows bear the scars of craters formed by asteroids and comets crashing onto the surface at speeds of tens of kilometers per hour. Younger lava flows have flooded the floors of some of the older and larger craters, and there are over a hundred sites where volcanic explosions have ruptured the surface from below.
BepiColombo captured this view of Mercury on October 1, 2021, as the spacecraft flew past the planet for a gravity assist maneuver. The image was taken at 23:41:12 UTC by the Mercury Transfer Module’s Monitoring Camera 2 when the spacecraft was 1410 km from Mercury. Credit: ESA/BepiColombo/MTM, CC BY-SA 3.0 IGO
BepiColombo will analyze these themes in order to better understand this mysterious planet, building on data collected by NASA’s Messenger mission. It will give answers such as: What are the volatile substances that violently transform into gas to power volcanic explosions? How did Mercury keep these volatiles despite the fact that most of its rock had been stripped away? How long did the volcanic activity last? How quickly does the magnetic field of Mercury change?
“In addition to the images we obtained from the monitoring cameras we also operated several science instruments on the Mercury Planetary Orbiter and Mercury Magnetospheric Orbiter,” adds Johannes Benkhoff, ESA’s BepiColombo project scientist. “I’m really looking forward to seeing these results. It was a fantastic night shift with fabulous teamwork, and with many happy faces.”
The main science mission of BepiColombo will begin in early 2026. It is using nine planetary flybys in total: one at Earth, two at Venus, and six at Mercury, along with the spacecraft’s solar electric propulsion system, to help steer into Mercury orbit. The next Mercury flyby will occur on June 23, 2022.
READ MORE: Why Isn’t Our Moon a Planet?
