Looking for Life on Venus

Dr. S. S. VERMA; Department of Physics, S.L.I.E.T., Longowal; Distt.-Sangrur (Punjab)-148 106

2020-09-20 14:18:05

Credit: pixabay.com

Credit: pixabay.com

Based on the mythologies of the concept of life in almost all cultures, man has always believed in a philosophy that he is not alone in this universe and life must be there somewhere else. Thus, searching for life (just like earth) anywhere else in the universe is an everlasting goal of science and technology well supported by the public and planners view and aspiration.  Science and technology people are always busy in finding the possible signs of alien life anywhere else.

Various space explorations do have the core concept behind to look for such signs of aliens. Electronic signals are not only propagated but signals prevailing in the space are also being intercepted and analysed to search for any extra-terrestrial communication. Science and technology no doubt has progressed to such a level that investigating tools are exploring different parts of the universe in search of life signals. Recently, the detection of phosphine in Venus’ clouds is a big deal towards finding out if it’s a sign of life.

Venus, a second nearest to the sun, planet in our solar system is termed a symbol of love and beauty in mythology and is the second-brightest natural object in the night sky after the Moon. Venus can cast shadows and sometimes can be visible to the naked eye even in broad daylight. Venus lies within Earth's orbit so never appears to venture far from the Sun and either sets in the west just after dusk or rises in the east a bit before dawn. Venus orbits the Sun every 224.7 Earth days and with a rotation period of 243 Earth days, it takes longer to rotate about its axis than any other planet in the Solar System. Venus does so in the opposite direction to all but Uranus meaning the Sun rises in the west and sets in the east for Venus. Venus does not have any moons just like Mercury; a distinction among planets in the Solar System. Venus, as one of the brightest objects in the sky, has been a major fixture in human culture for as long. It has not only been made sacred like to gods in many cultures but has been a prime inspiration for writers and poets as the "morning star" and "evening star". Venus was the first planet to have its motions being plotted across the sky, as early as the second millennium BC. 

Venus is an earthly planet and is sometimes even called as Earth's "sister planet" because of their similar size, mass, proximity to the Sun, and bulk composition. Though, it is radically different from Earth in other respects and has the densest atmosphere of the four terrestrial planets, consisting of more than 96% carbon dioxide. The atmospheric pressure at the planet's surface is about 92 times the sea level pressure of Earth, or roughly the pressure at 900 m (3,000 ft) underwater on Earth. Venus has the hottest surface of any planet in the Solar System with a mean temperature of 737 K, even though Mercury is closer to the Sun. Venus is shrouded by an opaque layer of highly reflective clouds of sulphuric acid, preventing its surface from being seen from space in visible light. It is imagined to have had water oceans in the past which might have vaporized through the photo dissociation process as the temperature rose due to a runaway greenhouse effect. The free hydrogen might have been swept into interplanetary space by the solar wind because of the lack of a planetary magnetic field. Venus' surface is a dry desert scape interspersed with slab-like rocks and is periodically resurfaced by volcanism. Due to its proximity to Earth, Venus has been a prime target for early interplanetary exploration. Venus has already attracted the attention of astronomers and planetary scientists and explorers and  was the first planet beyond Earth visited by a spacecraft  Mariner 2 in 1962, and the first orbiter to be successfully landed on by Venera 7 in 1970. The thick clouds on Venus' atmosphere rendered observation of its surface impossible in visible light.  The first detailed maps of Venus did not emerge until the arrival of the Magellan orbiter in 1991. Further plans have been proposed for rovers or more complex missions, but they are hindered by Venus' hostile surface conditions.

The possibility of life on Venus became a topic of research when in September 2020 phosphine gas, a biomarker, was detected in its clouds, in concentrations higher than can be explained by any known abiotic source. Phosphine (PH?) is a toxic gas made up of one phosphorus and three hydrogen atoms. This gas is commonly produced by organic life forms and difficult to make on rocky planets. It was discovered in the middle layer of the Venus atmosphere which raises the tantalizing possibility that something is alive on our planetary neighbour. With this discovery, Venus joins the high ranks of other three terrestrial planetary bodies i.e., Mars, the icy moons Enceladus and Europa where life may once have existed, or perhaps might even still do so today. This discovery about Venus is one of the most exciting and opens up a new set of possibilities for further exploration in search of life in the Solar System.

The discovery team identified phosphine at Venus with the use of two different telescopes, helping to confirm the initial detection.  Phosphine gas can also be generated from several processes that are unrelated to life, such as lightning, meteor impacts or even volcanic activity. However, the quantity of phosphine detected in the Venusian clouds seems to be far greater than these processes are capable of generating, letting the team rule out numerous inorganic possibilities.  Taking into record the unexplored Venus surfaces so far due to its inhospitable atmospheres, planetary scientists are forwarding two possibilities to explain the detection of phosphine gas. Which indicates that either there is some sort of life in the Venus clouds-generating phosphine or there is unexplained and unexpected chemistry taking place there.  To confirm it further, more information about the abundance of PH? in the Venus atmosphere is needed, and we can learn something about this from Earth. The existing telescopes capable of detecting phosphine around Venus can be used for follow-up observations, to both definitively confirm the initial finding and figure out if the amount of PH? in the atmosphere changes with time. There is now a huge opportunity to carry out lab work to better understand the types of chemical reactions that might be possible on Venus and for which very limited information is available at present.

Spacecraft equipped with spectrometers that can detect phosphine from orbit could be dispatched to Venus with the express purpose of characterizing where, and how much, of this gas is there. Because spacecraft can survive for many years in Venus’ orbit and could transmit continuous observations with a dedicated orbiter over a much longer period than with telescopes on Earth. But even orbital data can’t tell the whole story and to fully understand what’s happening at Venus, we have to actually get into the atmosphere with the help of aerial platforms. Capable of operating above much of the acidic cloud layer - where the temperature and pressure are almost Earth-like - for potentially months at a time, balloons or flying machines could take detailed atmospheric composition measurements and these machines could even carry the kinds of instruments being developed to look for life. At that point, humanity might finally be able to definitively tell about the possibility of life on Venus. Thus, Venus being a compelling exploration target, with tantalizing evidence that the planet once had oceans and perhaps even suffered a hellish fate at the hands of its own volcanic eruptions with the detection of a potential biomarker in its atmosphere, scientists now have major reason to return to the exploration of Venus for a possibility of life.