Phosphine is a molecule that consists of one phosphorus and three hydrogen atoms. It is a very toxic gas. The only way phosphine is produced on Earth is by anaerobic bacterias that do not require oxygen for growth. We know that phosphine is common in Jupiter and Saturn's atmospheres and scientists believe that under extreme pressure and temperature this gas can be produced in a non-organic way. Phosphine was discovered in the atmosphere of Venus on 14 September 2020 by the James Clerk Maxwell Telescope JCMT at Mauna Kea Observatory in Hawaii. The result of the study shows that there is a lot of Phosphine in the atmosphere. The UV light from the Sun should destroy the molecules and that suggests that something is producing new Phosphine and that process cannot be explained by chemical reactions. Perhaps there are extreme conditions on Venus that could produce this gas, in a way that we don’t know about yet or it is a sign of life.
Image credit: NASA/JPL-Caltech
At 50-60 kilometers altitude in Venus' atmosphere, the pressure is the same as Earth and also the temperature. Perfect conditions for airborne bacterial life to thrive and it was just at that altitude the Phosphine gas was discovered. The surface at Venus is about 465°C and the pressure 90 times earth. The interest of sending missions to Venus to search for life has been low before the findings. The focus has been on Mars because the planet's surface has better conditions for that.
A Japanese space probe Akatsuki has since 2010 been studying the atmosphere of Venus and in a few years, we will get data from Venus upper atmosphere, which could give us an explanation of what is producing Phosphine.
Several missions to Venus have been conducted in the past. Actually Venus was the first planet that was visited by a space probe in 1962, Mariner 2 flew within 34,400 kilometers of the surface of Venus. Venera was a series of probes developed by the Soviet Union to study Venus. Venera 7 was the first probe to land on Venus in 1970. It sent data to Earth for 23 minutes before it stopped working because of the heat.
In light of the new findings, NASA said we should prioritize Venus for new missions. The missions that have been proposed before the findings are:
The Venera-D spacecraft was proposed to Roscosmos in 2003. It would be launched in 2026 or 2031 it would include a lander. NASA is working with Russia on the mission concept.
India's ISRO is developing the Shukrayaan-1 orbiter. It is proposed to be launched in 2023