Venus-Can it harbor life?
A comprehensive description of the recent discovery regarding Venus and the future of Venus Research and Exploration.
The search for life beyond Earth has revolved mainly around our red neighbour, Mars. NASA has launched multiple rovers over the years to examine Mars’ dusty surface for signs of water and other habitability hints.
Now, in a surprising twist, a team of astronomers led by Jane S. Greaves, of Cardiff University and the University of Cambridge, have observed signs of life in the clouds of our even closer planetary neighbour, Venus. The researchers were able to make the detection with the help of the James Clerk Maxwell Telescope (JCMT) in Hawaii and the Atacama Large Millimeter Array (ALMA) observatory in Chile. They have not found direct proof of life; they have announced discovering traces of phosphine gas molecules on Venus. This revelation has caused great excitement because, given the chemical and geological composition of Venus, this can imply the existence of life forms that release this substance through biochemical pathways.
Why is phosphine gas considered as a biomarker of life?
The detected presence of phosphine on Venus does convey the possibility of life there. A molecule of phosphine gas consists of a phosphorus atom surrounded by three hydrogen atoms. On Earth, it is produced due to industrial activity. Anaerobic bacteria that live in oxygen-sparse environments also produce phosphine. After calculating the amount of phosphine in Venus’ atmosphere (20 parts per billion), researchers have estimated whether this amount of phosphine can be produced by some chemical and physical pathways such as sunlight, volcanoes erupting, surface minerals, meteor strike, and lightning. The other mechanisms could, at most, produce only ten-thousandth of the amount of phosphine that has been detected. However, they do not rule out the possibility that some unknown natural processes (photochemical or geochemical reactions) can produce this biomarker.
How can life survive on a hostile planet like Venus?
Earth is a habitable planet with moderate temperatures, just right for life to sustain. Venus’ surface is a boiling hot landscape, with temperatures reaching 900 degrees Fahrenheit and an oppressive air drier than the driest places present on Earth. However, there is a narrow, temperate band within Venus’ atmosphere, between 48 and 60 kilometres above the surface, where temperatures range between 30 to 200 degrees Fahrenheit. With much controversy, scientists have thought that if life exists on Venus, this layer of the atmosphere, or cloud deck, is likely the only place where it would survive. And to everyone’s surprise, it just so happens that this cloud deck is where the team observed signals of phosphine.
All eyes on Venus
Before seriously considering this possibility, scientists want to make sure whether phosphine is present on Venus. As it can be seen in the figure below, the dip in Venus’s JCMT spectrum gave the first evidence of the presence of phosphine on the planet. In contrast, the more detailed spectrum from ALMA confirmed that phosphine really is present in the Venusian atmosphere. Some researchers are not yet convinced and are waiting for someone else to confirm it. This is because only one absorption line for phosphine has been identified. So, astronomers are now hoping to detect phosphine using other telescopes like the NASA Infrared Telescope Facility in Hawaii; the other is on NASA’s Stratospheric Observatory for Infrared Astronomy, a plane that carries a telescope. Observations in the infrared and other regions of the spectrum will help scientists identify more absorption lines associated with phosphine, which might be more convincing.
Three international scheduled missions: Europe and Japan’s BepiColombo spacecraft, on its way to Mercury, and the European Space Agency’s Solar Orbiter and NASA’s Parker Solar Probe, both on their way to the Sun, might help in studying the Venusian atmosphere as they will fly close to Venus in the coming months. Observations by these spacecraft will be helpful because they wouldn’t be constrained by Earth’s atmosphere. But scientists are not sure if the designed instruments can detect phosphine in the Venusian atmosphere. BepiColombo has chances of detecting the gas in a fly-by this October, and a better chance next August, with its infrared instrument. The Parker Solar Probe, too, might be able to make a detection, with a device designed to study solar particles. There is also a spacecraft currently orbiting Venus: Japan’s Akatsuki mission, which entered orbit in 2015 and is studying Venus’s weather and searching for volcanism. Although it lacks the instrumentation required to spot phosphine directly, it could help in other ways.
Future missions
Missions that are still in development could be slightly changed to work on the detection of phosphine. The Indian Space Research Organization plans to launch a Venus orbiter called Shukrayaan-1 by 2025. The United States and Europe are also contemplating missions to Venus that could provide useful data on the planet’s potential habitability or even directly search for life signs. A proposed NASA mission called VERITAS to study Venus is a possibility.
In the meantime, if astronomers can confirm the detection of phosphine, they will want to rule out other possible methods for its production before considering that living organisms are producing it. Some astronomers are sceptical that phosphine on Venus indicates the presence of biology rather than a new chemical process. Unless we get more data, it is challenging to confirm life forms on Venus.
