Going to Venus

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

2021-07-02 11:55:41

Credit: pixabay.com

Credit: pixabay.com

Hunting for our likes (human) in the universe in general and in our own solar system in particular has always been at the fore front of scientific community. Space missions to moon, to mars and now to Venus are taken up by scientists and engineers to come out with new findings.  Venus has long played second fiddle to its redder, smaller, and more distant sibling: Earth. Venus, the second planet from the Sun, lies, on average, 108 million km from the Sun, about  30%closer than the Earth. Venus is often referred to as our sister planet because of similarities in size, mass, density and volume. It is believed that both planets share a common origin forming at the same time out of a condensing nebulosity around 4.5 billion years ago.

That is why that Earth and Venus do often get called planetary twins. On the other side, Venus has no surface water, a toxic, heavy atmosphere made up almost entirely of carbon dioxide with clouds of sulphuric acid and at the surface the atmospheric pressure is over 90 times that of the Earth at sea-level. Given how inhospitable we’ve learned Venus to be, we’ve spent the majority of the last century pinning some of our biggest hopes of finding signs of extra-terrestrial life on Mars. Recently, it was announced that a peculiar gas called phosphine had been spotted in the clouds above Venus. The gas is produced by microbes here on Earth, and after most known non-biological processes were ruled out, the discovery has renewed hopes that there’s life on Venus. So, answering questions about the possibility of life there will require not one but several new missions that can directly study the planet.

Venus is extremely bright, and many of the large ground-based telescopes cannot properly observe it. This brightness, caused by the intense reflection of sunlight from its thick clouds and highlighted by its close proximity to Earth, basically blinds our instruments from making detailed observations of the planet. Similarly, going to Venus is also next to impossible as temperatures at the surface of Venus reach a scorching 464°C, and pressures are 89 times higher than on Earth. Another anomaly between the two worlds is the rotation of Venus. Firstly, its axis of rotation is inclined at 177.36 degrees (compared to 23.5 degrees on Earth). This means that Venus rotates in a retrograde direction from east to west, making the Sun rise in the west and set in the east. Further to this the rotation is very slow: a sidereal day on Venus lasts 243 Earth days. This is even longer than a Venusian year which is only 224.7 Earth days.

A pressing question about the Venus involves finding out how similar the planet may have been to Earth in the planets' early histories. Venus' size is similar to Earth's and its distance to the sun would have put the planet in the "habitable zone" - the location where liquid water could exist on the surface - when the sun was younger and dimmer. Although Venus is now a raging inferno. Scientists want to know whether (as some suspect) the planet had liquid water for 3 billion years, what kind of surface geology and rock types it has, the nature of its dormant plate tectonics (which might be key to sustaining life) and how similar Venus might be to rocky exoplanets very close to their parent stars.

Earlier missions

Till now, only the Soviet Union has successfully landed on the Venusian surface-its Venera 13 lander functioned for 127 minutes before succumbing to the elements in 1982. It’s not easy to justify spending hundreds of millions or even billions of dollars on a mission that could be over in a matter of hours and not give us what we need.  So an orbiter is the most sensible start. Unlike ground-based observations, orbiters can peer into the atmosphere and would have a better time observing how phosphine or other potential bio-signatures change over time or over what regions they are most concentrated. The last major Venus orbiter was ESA’s Venus Express, which studied Venus for eight years until engineers lost contact with it, likely because it ran out of fuel. Currently, the only spacecraft exploring Venus is Japan’s Akatsuki orbiter, which arrived in 2015 to study the planet’s climate and weather. It’s doing good science, but it doesn’t have any instruments that could really probe atmospheric chemistry and look for signs of organic life.

Proposed missions

Using cutting-edge technologies that NASA has developed and refined over many years of missions and technology programs and after technological feats making possible to touch the surfaces of moon and mars successfully, NASA has planned 2 Missions to Study World of Venus by 2030. Venus is Earth’s nearest planetary neighbour. It is astounding how little we know about Venus, but the combined results of these missions will tell us about the planet from the clouds in its sky through the volcanoes on its surface all the way down to its very core. The missions aim to understand how Venus became an inferno-like world when it has so many other characteristics similar to Earth– and may have been the first habitable world in the solar system, complete with an ocean and Earth-like climate. It is anticipated that data from these missions will be used by the broadest possible cross section of the scientific community.

Mission DAVINCI+ (Deep Atmosphere Venus Investigation of Noble gases, Chemistry, and Imaging) will measure the composition of Venus’ atmosphere to understand how it formed and evolved, as well as determine whether the planet ever had an ocean. The mission consists of a descent sphere that will plunge through the planet’s thick atmosphere, making precise measurements of noble gases and other elements to understand why Venus’ atmosphere is a runaway hothouse compared the Earth’s. In addition, DAVINCI+ will return the first high resolution pictures of the unique geological features on Venus known as “tesserae,” which may be comparable to Earth’s continents, suggesting that Venus has plate tectonics. The results from DAVINCI+ could reshape our understanding of terrestrial planet formation in our solar system and beyond.

Mission VERITAS (Venus Emissivity, Radio Science, InSAR, Topography, and Spectroscopy) will map Venus’ surface to determine the planet’s geologic history and understand why it developed so differently than Earth. Orbiting Venus with a synthetic aperture radar, VERITAS will chart surface elevations over nearly the entire planet to create 3D reconstructions of topography and confirm whether processes such as plate tectonics and volcanism are still active on Venus. VERITAS also will map infrared emissions from Venus’ surface to map its rock type, which is largely unknown, and determine whether active volcanoes are releasing water vapor into the atmosphere.