The discovery of phosphine on Venus this week made waves across the astronomical community and beyond. We all want to know what is creating this peculiar gas. Is it a living organism or some chemical processes the like of which we have never seen on Earth? There are many discussions of sending missions there, but coincidentally a mission will already be there in just a few weeks.
BepiColombo is a joint European-Japanese mission on its way to study Mercury. On its way there, it will fly by Venus twice, the first time on October 15, 2020, and the second on August 11, 2021. The team will test its instruments to check everything is working well and, in an attempt to catch two birds with one stone, study the clouds of Venus.
One instrument in particular should have the potential to spot phosphine. The MErcury Radiometer and Thermal Infrared Imaging Spectrometer (MERTIS) has the range to observe at least two emission lines that are unique to phosphine. “We possibly could detect phosphine,” ESA's Johannes Benkhoff, BepiColombo's project scientist, told Forbes. “But we do not know if our instrument is sensitive enough.”
The spacecraft is also not in an ideal position to study the planet with the detail and attention potentially needed for the sought-after phosphine detection. The spacecraft will pass at about 10,660 kilometers (6,260 miles) from the planet, but the position of MERTIS' main camera won’t be in the right place to see Venus. This detection job will have to be conducted by the calibration camera, according to New Scientist.
A few weeks until the flyby is not enough time to make adjustments, but the team will have another chance to take a good look at Venus. In August 2021, BepiColombo will be only 550 kilometers (340 miles) from the planet when it passes by again. This should be enough time to prepare the spacecraft for a better chance to see phosphine.
If neither of these two observations is successful, don't worry too much. There are observation proposals from telescopes on Earth and several missions proposed to explore the planet. Two of the four finalists of NASA’s Discovery Program, DAVINCI+ and VERITAS, are missions to study Venus. The European Space Agency and the Indian Space Agency are also looking into missions to Venus. Detailed answers on the origin of phosphine might be just a few years away.