Calling on the neighbours: ISRO's upcoming Venus, Mars missions explained

In the past decade and a bit, India has not only landed on the moon on a shoestring budget—a great achievement on its own—but has also successfully orbited Mars, the only country to do so in its first try.

Buoyed by the success and worldwide recognition, the Indian Space Research Organisation has now set its sights on landing on the red planet, as well as orbiting the hostile neighbour Venus, often called earth’s twin.

The Union cabinet approved Shukrayaan (Venus Orbiter Mission) in September 2024 with a budget of Rs1,236 crore, much lower than those of similar foreign missions. Two years later, after completing its preliminary design review this April, the spacecraft is now on track to be launched on March 29, 2028.

On July 19 the same year, it is expected to enter a specialised elliptical orbit ranging from 500km above the Venus surface at its closest point to 60,000km at its farthest, positioning its instruments perfectly to capture data from varying altitudes. The launch vehicle is likely to be ISRO’s powerful LVM-3 rocket, which also launched Chandrayaan 3.

Mangalyaan 2, on the other hand, is expected to be launched in 2030, and will build on the previous mission. “Globally, the game has moved from ‘is Mars habitable’ to ‘bring rocks home and get ready for people,” Sam Richards, director of the UK’s Meridian Space Command, told THE WEEK. “America and Europe are working on sample return, China is going for its own, Japan is targeting the martian moon Phobos. India’s next mission plays a different role: proving it can land on Mars, which only the Americans and Chinese have pulled off. Getting down through the martian atmosphere is the hardest few minutes in spaceflight, and it is littered with wreckage from agencies that got it nearly right. One note of caution: Mars launch windows only come around every couple of years, so I’d treat any published dates as ambitions rather than promises.”

Why Venus?

“Venus is suddenly popular again,” said Richards. “India’s mission, NASA’s DAVINCI and VERITAS, and ESA’s (European Space Agency) EnVision, they are all chasing the same basic question: Venus and earth started out as near twins, so what went wrong? India’s mission will look at the surface and what’s underneath it, the atmosphere, and how the planet interacts with the sun.”

Venus has always puzzled scientists—the planet is permanently wrapped in clouds, made of corrosive sulphuric acid, which means radars or probes that have given us data so far did so in a couple of hours before being cooked. It’s the closest planet to earth, but, in many ways, we know the surface of Pluto better.

Richards said Shukrayaan would reveal a lot more than earlier missions. “The headline is the radar that looks beneath the surface, which nobody has done on Venus before,” he said. “Older missions tended to do one thing, or look at one region. This one carries 19 instruments and watches the whole planet over time, so it can catch things like active volcanoes actually erupting rather than just evidence that they once did.”

Think of it like using X-rays to see through skin and examine bones—the radar will see through the dense atmosphere to study mountains, valleys and geological features.

Together, missions such as Shukrayaan, DAVINCI and Russia’s proposed Venera-D aim to unlock Venus’s atmospheric mysteries, geological evolution, volcanic activity, climate history and interactions with solar wind.

“India’s contribution is especially significant because multiple independent missions observing the same planet from different perspectives will generate complementary datasets, enabling scientists to build the most comprehensive understanding of Venus ever achieved,” said Srimathy Kesan, the founder of Space Kidz India, an aerospace company in Tamil Nadu.

Both earth and Venus were born from the same solar nebula, and have similar size, mass and rocky compositions. Yet, today, earth supports life while Venus doesn’t. Understanding why could be one of the greatest scientific revelations of the century.

“Venus offers us a natural laboratory to study the long-term effects of greenhouse warming, atmospheric evolution, planetary climate change, water loss and geological transformation,” said Kesan. “Every discovery made on Venus ultimately enhances our understanding of earth’s past, present and possible future. In many ways, it is a mirror reflecting what earth might have become under different conditions.”

But there are also major differences. For instance, Venus has no moons and rotates slowly in the opposite direction of most planets, making its day longer than its year. A day on Venus is 243 earth days; a year is 225. The sun rises in the west and sets in the east.

“Venus has an average surface temperature hot enough to melt lead,” said space expert Girish Linganna. “This temperature is maintained by a thick layer of carbon dioxide and sulphuric acid clouds that trap most of the incoming solar radiation. The atmosphere of Venus is about 90 times denser than that of earth, which exerts a pressure equivalent to being 1km underwater on earth. The atmosphere also contains traces of other gases, such as nitrogen, carbon monoxide and sulphur dioxide.”

Carl Sagan, the famous astronomer, once compared Venus to hell. And that is what awaits the many missions. Not only would keeping electronics alive be a major challenge, but missions also plan to use the atmosphere itself to adjust the orbit, which is tricky when they don’t fully know what the atmosphere will do. “Venus might have signs of life in its upper atmosphere, too, where some microbes could survive the harsh conditions,” said Linganna. “Some scientists have proposed that phosphine, a gas usually associated with biological processes, could be produced by living organisms in the clouds of Venus. However, this [is only a] hypothesis. Venus is a planet that challenges our understanding of planetary science and astrobiology. It is a world of contrasts and contradictions, but also of similarities and possibilities.”

To explore this world, India has partnered with Sweden’s National Space Agency, with an MoU being signed during Prime Minister Narendra Modi’s visit to Gothenburg in May. “Under the space agreement, the Swedish Institute of Space Physics will provide a special scientific instrument called the Venusian Neutrals Analyser (VNA),” said Linganna. “This sensor will be integrated into a larger plasma package named VISWAS (Venus Ionospheric and Solar Wind particle AnalySer), developed by India’s Space Physics Laboratory in Thiruvananthapuram. The mission will carry 19 scientific payloads, with key international contributions also coming from Russia’s Space Research Institute.”

So, what does this VNA actually do? “The sun constantly releases tiny charged particles into space, which scientists call solar wind,” said Linganna. “When these particles strike Venus, they push out gas particles from its upper atmosphere. The VNA will measure these escaping particles to understand how Venus has slowly lost its atmosphere over millions of years. This is important because it can give clues about earth’s own future and how planets change over time.”

But why Mars again?

The underground, mostly. If there is still water on Mars, and possibly if there was ever life, the evidence is buried, and humans have barely scratched the surface. As for the fascination: Mars could be the answer to the biggest question we have, which is whether we are alone.

Future Mars missions are increasingly focused on understanding whether the planet once supported microbial life, investigating underground water reservoirs, studying climate evolution and exploring the planet’s geological history. These would entail a much more integrated exploration architecture—consisting of an orbiter, lander, rover, and potentially aerial exploration platforms—to help scientists observe Mars from multiple perspectives simultaneously.

As for India’s mission, one of the most interesting aspects is the inclusion of the Martian Boundary Layer Explorer (MARBLE), a sophisticated drone designed to soar at 100m above the martian surface. Inspired by NASA’s Ingenuity and equipped with an advanced instrument suite, this drone will do a vertical profile of the atmosphere, gathering data on temperature, atmospheric pressure and composition at different heights. This information would unlock secrets vital for future missions, enabling us to predict dust storms, wind patterns and other hazards. By studying the composition of the atmosphere at different altitudes, scientists can gain insights into the planet’s past and its dramatic transformation from a warmer, wetter planet to the cold, dry world we see today.

“A rover gives you depth, a drone (MARBLE) gives you reach. The rover stops and does proper geology, but it is slow, covering metres a day,” said Richards. “The drone can scout kilometres ahead, investigate terrain no rover could ever reach, and tell the rover where it’s actually worth going. Ingenuity proved the idea works, so now it is about building on that and pushing it further.”

Though not as hostile as Venus, Mars does throw up challenges for spacefarers. The temperature on its surface can plummet to as low as minus 90 degrees Celsius at night, challenging the durability and design thresholds of drone components. Additionally, there is the challenge of powering the device: Mars gets less than half the solar energy that earth does.

It’s a challenge ISRO wants to face. “Mangalyaan 2 represents an important milestone because it signals the country’s evolution from demonstrating interplanetary capability to conducting more ambitious planetary science and surface exploration,” said Kesan. “This transition is a remarkable leap in engineering complexity. Entering the martian atmosphere, surviving hypersonic descent, executing autonomous landing, and conducting surface operations require technologies far more advanced than orbital navigation. If successful, Mangalyaan 2 will mark India’s transition into an elite group of nations capable of exploring planetary surfaces rather than merely orbiting them.”