Science and Technology

Love thy neighbour

M Ramesh | Updated on June 20, 2021

Five missions are lined up to Venus, a planet so near yet so mysterious

The goddess of love and our closest neighbour, Venus, is back in the telescopes of space agencies.

Earlier this month, US space agency NASA announced two missions to Venus — Davinci and Veritas; a week later, the European Space Agency bunged in one more (EnVision). Add to these the previously planned Venera-D of Russia and, not to forget, India’s own Shukrayaan, scheduled for launch a little later, and you have a palette of instruments to check out the hot neighbour.

All these missions will likely happen in the second half of this decade; after all, Venus is hard to win over. Venus missions, even orbiters that merely circle the planet, are tough because of the extreme conditions. In fact, a central theme running through all these missions is to understand why Venus evolved so differently than Earth. Compared with Venus, a Mars mission is like landing in Dubai.

Extremely hot clouds of sulphuric acid abound in the thick carbon dioxide atmosphere of Venus — the atmospheric pressure there is about 90 times what we feel on our skins here. Since temperature goes up when pressure goes up, the planet is also hot — five times as hot as boiling water.

If you stand on the Venus surface (which, by the way, is very rugged with many plateaus) and look at the sky, you will find it orange. Venus has a very small axial tilt of 3 degrees, compared with Earth’s 23.5 degrees, which means its axis of rotation is almost perpendicular to the plane of its revolution around the sun. Consequently, there are no seasons.

Also, Venus spins so slowly around itself that in the duration between two sunrises there, the Earth would have completed 245 days — and Venus itself would have gone around the sun once. Venus is one of the only two planets that spin clockwise — the other being Uranus — which means that the sun rises in the west and sets in the east.

Venus is, therefore, a very interesting planet but we know precious little about it — even though it lies in the inner solar system (the rocky planets up to Mars).

Exploration of the outer solar system — which has gaseous planets — is more difficult and expensive, whereas humans have developed spacecraft, orbiters and landers for those in the inner. Yet, Venus remains a mystery. “It is astounding how little we know about Venus,” says Tom Wagner, a NASA scientist.

Incidentally, among the five announced Venus missions, only the Russian’s features a lander — the others stay contented with orbiters.

The Shukrayaan mission has been delayed due to the pandemic but ISRO is in the process of finalising the payloads. There are some noteworthy features about the mission. First, the orbiter will have 100 kg of scientific payload, compared with the 14 kg of Mangalyaan. It is understood that there will be 12 Indian scientific instruments and eight foreign ones. Accommodating foreign instruments is more a diplomatic and soft-power matter.

Second, ISRO has not called it a ‘technology demonstration’ or TD mission. This, to some experts, implies a growing confidence, as TD sounds pretty defensive.

Third, the mission reveals ISRO’s mindset, showing the agency prefers to spread its resources across several missions — Chandrayaan, Mangalyaan, Gaganyaan, Aditya and Shukrayaan — rather than focus on one. There could be different views about this approach. Chaitanya Giri, an astromaterials scientist and a Fellow of the Gateway House Space and Ocean Studies Program, approves, noting that the missions ought to be looked at as technology incubators.

Published on June 20, 2021

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