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What makes ISRO's Venus mission extremely challenging

Venus is not the most welcoming of planets

venus-northern-hemisphere-nasa-magellan-spacecraft-nasa Representational image | Shutterstock

As ISRO gets ready to work towards its planned Venus mission, scheduled for December 2024 launch, space and aerospace experts feel that though it is a fascinating mission, it is also expected to be one of the most challenging tasks that the national space agency has ever undertaken.

Venus is not the most welcoming of planets. It is scorching hot because a majority of its atmosphere is composed of carbon dioxide. Temperatures on the surface of Venus, owing to the consequent extreme greenhouse effect, can reach up to 870 degrees Fahrenheit (470 degrees Celsius). The surface is said to be hot enough to melt lead, and dappled with innumerable volcanoes. While most of these volcanoes are believed to be dormant, some may still be active.

Venus is also infamous for its extreme surface air pressure— about 90 times higher than the pressure at sea level on Earth.

Since ancient times, Venus has always captured the imagination of people. Experts point out that though mythologies present Venus as a beautiful planet, it is completely inhospitable and resembles depictions of hell. This is why Venus has to be studied to understand how the planet was formed, if it was hospitable at any point and the factors that may have led to it being inhospitable.

“Studying Venus helps get a better understanding of the evolution of the planet, especially the study of exoplanets. The proposed scientific payloads of Shukrayaan are amazing. Unlike Mars, Venus has a thick atmosphere. Visual imagining payloads will not help in understanding the sub-surface topologies. The synthetic aperture radar (SAR) payload on board Shukrayaan will throw more light on revealing the hidden secrets of the Venusian surface or subsurface. Studying the thick Venus atmosphere will also pave the way for future air balloon type missions which can float in the upper atmosphere where the conditions are more benign than that on the ground. Geologists and planetary scientists world over will be heavily benefited from the science that this mission will bring. Also, ISRO has chosen a two-tonne class satellite platform, which allows more scientific instruments, to bring out the best science possible from one single mission,” explained Rohan Ganapathy, CEO and CTO of Bellatrix Aerospace.

Venus has been an object of great interest and target of observation for millennia. The ancient Babylonians tracked its wanderings through the sky in records that date as far back as 1600 BC. The Greek mathematician Pythagoras was the first to discover that the brightest stars in the morning and evening sky were in fact the same object, Venus.

As per ISRO, December 2024 is a likely launch date for a mission to Venus. The date has been chosen keeping in mind the fact that Venus will be in close proximity to Earth in the year 2025. When Venus and Earth are in such close proximity, a spacecraft can be placed in Venus’ orbit with the least amount of propellant. The next similar window is slated only in 2031. ISRO is planning a number of experiments as part of the mission, including investigation of the surface processes and shallow subsurface stratigraphy, along with the active volcanic hotspots and lava flows. It also intends to study the structure, composition, and dynamics of the atmosphere and investigate solar wind interaction with the Venusian Ionosphere.

ISRO also wants to examine the Venusian surface, which is covered by dense clouds that make it impossible to view the planet's surface through a key instrument on the spacecraft—the high-resolution synthetic aperture radar.

“While Venus is not nearly the largest planet of the solar system, its proximity to Earth makes it the brightest of the planets in the sky. It also qualifies as the second brightest object in the night sky, after only the moon. In fact, a pilot aboard an Air Canada flight is known to have mistaken the dazzling planet for an oncoming aircraft. The pilot sent his plane into an emergency dive to avoid a midair collision, the Canadian air transportation officials reported earlier,” remarked Girish Linganna, space and aerospace expert and the director, ADD Engineering Components India Limited.

Linganna said winds swipe across Venus at nearly 450 miles an hour (724 kph) in its middle cloud layer. “The atmosphere of Venus is made mostly of poisonous sulphuric acid. Since Venus orbits the sun within Earth's orbit, the planet appears to have phases like the moon. When Venus is on the opposite side of the sun, it is in full phase, while it appears in a new phase when it is between the Earth and the sun. Despite the poisonous atmosphere, a chemical called phosphine was discovered in Venus's clouds recently. Incidentally, on Earth, phosphene is found to be produced by microbes. The study seemed to suggest that despite its extreme conditions, Venus might, after all, host life. Needless to say, the theory was disputed and alternate explanations were posited.”

He pointed out that landing on Venus' surface can be an extremely challenging affair. “A lander (or rover) must fall through approximately 35km (1,00,000ft) of the thick, murky lower atmosphere before the final couple of kilometers where the ground finally becomes visible from above. During descent, the temperature starts at a comfortable 20 degrees Celsius and shoots up to 450 degrees Celsius just before reaching the surface. (A standard kitchen oven runs at about 200 degrees Celsius.) Near the surface, the air is so thick that the lander will settle to the ground much like a stone settles in water—no retrorockets or sky cranes are required,” Linganna said.

Space experts observed though there have been more than 40 missions to Venus so far by different space agencies, India is just at the infancy of Venus exploration due to the short mission spans. “It is a great challenge to get closer to Venus as it has a dense atmosphere. We don't know the changes that have happened in the past few decades, and it is hard to predict about space as it always surprises us. This can turn out to be a hell of an entry into the Venus orbit. We have to wait and watch how this whole exploration program of Shukrayan-1 turns out to be. It is very exciting and I hope we make it successful considering neighbouring countries' experiences from the past. The ISRO chairman has cautioned against repeating experiments conducted by previous missions to Venus and focus on unique high impact outcomes as were achieved by the Chandrayaan-I and the Mars Orbiter Mission which is quite interesting to look forward to,” remarked Srimathy Kesan, founder and CEO, Space Kidz India.