Peak hour on Red Planet

IF you gaze into the northwestern evening sky tonight, you will spot a quite obvious reddish-orange point of light.

It looks like a coloured star, but it is actually the planet Mars, which has been very much in the news recently.

Over the past few weeks, three separate spacecraft from three sovereign states — the United Arab Emirates (UAE), China, and the US — have arrived at the Red Planet, and all are doing well.

The close timing of the arrival of each craft in this “armada’’ is not a coincidence. Each was launched in mid-2020, during a launch “window’’ only a few weeks long. Such opportunities last for only a short period about every two years and two months. At launch, Earth and Mars need to be in the correct relative places in their orbits so that when the spacecraft arrives at the orbit of Mars, Mars is in that part of its orbit at the time.

There would have been a fourth craft arriving — the European Space Agency’s Rosalind Franklin rover of the ExoMars 2020 mission — but that has been delayed until the 2022 launch window due to difficulties arising from the COVID-19 pandemic.

First of the trio to arrive was the UAE mission, called Hope, which is that country’s first interplanetary mission and is a joint project with the US. Hope entered orbit around Mars on the morning of February 10 our time, and it soon sent back a very fine picture of the planet, showing the famous trio of shield volcanoes known as Ascraeus Mons, Pavonis Mons and Arsia Mons.

In the Hope image of Mars, the planet appears about half full, exhibiting a slightly crescent shape. This is because at the time, the craft was above the terminator, the dividing line between day and night. We see the moon appearing to have this shape often, because the moon, too, experiences day and night as it rotates every 27.3 days. Mars rotates every 24.6 hours, so the length of its day is very similar to a day on Earth.

Hope will study various aspects

of the Martian atmosphere and weather, and try to provide some clues as to why the Martian climate has changed so much over Mars’ history.

Shortly after the arrival of Hope, the Chinese spacecraft Tianwen-1 arrived. This is the first Chinese spacecraft to arrive at Mars, and it carries a rover that will descend to the surface in a few months. It is a very ambitious mission, being an orbiter-rover combination. The orbiter will study the planet from above, using various instruments, including a camera for high-resolution images and even a radar instrument that will map Mars’ ice. Among the lander’s equipment will be a subsurface two-channel ground-penetrating radar,

which will study two different depth ranges extending down to about 100m. It is possible that this will reveal the presence of patches of water.

Just eight days ago was the arrival of the third craft — the United States’ Mars rover called Perseverance. It is the most sophisticated rover ever sent to Mars. Among many other activities, it will search for signs of life, and conduct an experiment to convert carbon dioxide in the Martian atmosphere to oxygen.

It has also carried to the surface the first interplanetary helicopter, a device with a mass less than 2kg called Ingenuity. Both the rover and the helicopter are doing well, and each has “phoned home’’ since the landing.

We have already seen some spectacular images, including video of the landing. In one sequence, the rover is seen during its descent, and the red Martian dust is seen being stirred up by the downwardfacing thrusters of its sky crane, which lowered the rover to the surface.

That view of the Martian dust blowing around reminded me of the famous footage taken from the lunar module Eagle as it descended to the lunar surface during the Apollo 11 mission. As Eagle neared

the surface, we heard the famous words from Buzz Aldrin: “Picking up some dust”.

Over the next year or two, we shall be learning a lot more about Mars. A key question for everyone is: Has there ever been life on Mars?

A “yes’’ answer would have a dramatic effect on how we think of ourselves, and the possibilities of life elsewhere in the universe.