Space Programme

Martian chronicles

China launches its first planetary probe to look for water on Mars


Tianwen-1 mission takes off

Turns out you can’t just launch a Mars mission at any old time. There is a brief window of opportunity every 26 months when the Red Planet aligns with Earth, vastly reducing the distance between the celestial bodies.

This window is the reason that three Mars launches have been scheduled for late July: the UAE’s Hope probe (launched July 20), China’s Tianwen-1 (launched July 23) and America’s Perseverance (launched yesterday).

The Tianwen-1 is China’s second attempt at a Mars mission – in 2011 it launched the Yinghuo-1 orbiter in conjunction with a Russian spacecraft. Unfortunately, the burners on the Russian craft did not activate at the crucial moment, causing the two vehicles to fall back to earth.

This time China used its own rocket, and the Tianwen-1 rover has its own delivery system designed to get it all the way to the Red Planet, including the so-called ‘seven minutes of terror’ – the infamously difficult journey from the top of the planet’s thin atmosphere (where temperatures reach 870 degrees centigrade) to its windswept surface.

A total of 44 Mars exploration missions have been launched since 1960s, Xinhua noted, but only about half have succeeded. The success rate for landing is even lower, and only the United States has succeeded in a soft landing on Mars, leading many scientists to dub the planet “the space graveyard”.

Therefore, if China succeeds in getting its first rover onto Mars intact it will be a huge achievement.

“Mars exploration is one of the important symbols of a space power. The successful implementation of China’s first Mars exploration mission will put China in the advanced ranks of international space exploration,” the Beijing Evening News quoted Zhao Xiaojin, a Party official with responsibility for space exploration as saying.

The Tianwen-1, whose name is taken from the title of a 2,200 year-old Chinese poem meaning ‘questions to heaven’, is expected to reach Mars in February next year. After entering orbit, it will then spend another two to three months surveying suitable sites for landing.

If all goes to plan it will then spend 90 Mars days (one Mars day is equivalent to one day and 37 minutes on Earth) exploring the planet’s surface using an orbiter satellite and a rover. The six-wheeled rover will deploy ground-penetrating radar to study Mars’ internal structure and look for pockets of water, according to state media.

In order to land safely on Mars the rover will have to reduce its speed from 20,000 kilometres an hour as it enters the planet’s atmosphere to almost zero as it makes contact with the surface. To do this it will need to deploy reverse boosters and a parachute. It will also have to hover over the planet’s surface to find a flat site for landing.

China has emerged as an ambitious and competent space power in recent years, with the country landing a rover on the far side of the moon in January 2019 – a first in human history (see WiC436).

It is also building a manned-space station – the core model of which is scheduled to be launched later this year.

To celebrate Tianwen’s successful launch CCTV scheduled a 10-part mini documentary Hello Mars detailing the technical challenges the scientists have had to overcome.

The Beijing News pointed out that Tianwen-1 was launched on time despite the coronavirus outbreak earlier this year.

“At a time when the US is provoking troubles and suppressing China’s science and technology, the launch is a vivid portrayal of China’s aerospace spirit, and a powerful symbol of economic and social recovery,” the newspaper added.

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