Europe and Japan’s BepiColombo spacecraft has successfully completed a flyby of Venus on its way to Mercury – which included an effort to look for phosphine, a possible biosignature, in the atmosphere.
Overnight at 11:58pm Eastern Time yesterday, October 14, the spacecraft flew 10,720 kilometers above the surface of Venus. The flyby is one of several being used to slow the spacecraft so it can enter orbit around our Solar System’s innermost planet, Mercury, in late 2025.
While the flyby is predominantly designed for trajectory reasons, it was also an opportunity for the mission teams to test their instruments and cameras. This included taking images of Venus, and more excitingly, using an instrument to look for possible signs of life in the atmosphere of the planet.
Last month, scientists announced the possible discovery of phosphine on Venus, a potential signature of life. On Earth, phosphine can be produced by certain anaerobic microbes. It’s thought the same could be true in the atmosphere of Venus, where airborne microbes float above the harsh conditions on its surface.
BepiColombo, launched in October 2018, was always planned to fly past Venus now. But the fortuitous timing meant the team could tailor the flyby somewhat to follow-up Earth-based observations to look for more evidence of phosphine at the planet itself.
“We possibly could detect phosphine,” Johannes Benkhoff from the European Space Agency (ESA), BepiColombo’s Project Scientist, told me last month. “But we do not know if our instrument is sensitive enough.”
The instrument the team are using to look for phosphine is called called MERTIS (MErcury Radiometer and Thermal Infrared Spectrometer). Designed to study the composition of the surface of Mercury, it may also be able to study the atmospheric composition of Venus.
However, this October flyby came very soon after the announcement of phosphine. As such, the team aren’t confident they had time to prepare the spacecraft to look for it. More promising is the spacecraft’s next flyby of Venus, in August 2021, when they will have much more time to prepare and the spacecraft will flyby much closer.
Aside from looking for phosphine, BepiColombo ran through a number of other tests too. With most of the team working remotely due to COVID-19, a small group of a handful of people oversaw operations from ESA’s mission control center in Darmstadt, Germany.
“The flyby itself was very successful,” Elsa Montagnon, ESA’s BepiColombo Spacecraft Operations Manager, said in a statement.
The spacecraft is actually comprised of two spacecraft, ESA’s Mercury Planetary Orbiter (MPO) and the Mercury Magnetospheric Orbiter (MMO) from the Japanese space agency (JAXA). While travelling together, the two will separate when they arrive at Mercury to carry out their separate missions.
ESA said that seven of the 11 instruments on the MPO, and three of the five instruments on Mio, were used during the Venus flyby. Now the team will be looking through the data they have collected, to see what sort of things they have learned about Venus.
“We hope to be able to provide some atmosphere temperature and density profiles, information about the chemical composition and cloud cover, and on the magnetic environment interaction between the Sun and Venus,” Benkhoff said in the statement.
In total BepiColombo is using nine flybys to reach Mercury orbit, which includes one of Earth (performed in April 2020), two of Venus, and six of Mercury. Last night’s flyby is the second of those nine, and now the spacecraft is well on its way to reaching Mercury.