Beijing, 5 May -- The search for life on Mars

Author Kang Yi

Looking at Mars from Earth, you will feel that it is bright and dark, east and west. The ancient Chinese therefore considered it "glowing with fire, separated from confusion", so it was called "glowing confusion". Plato, for his part, claims that it has a soul, and "if it is not an expression of free will, why does Mars have a retrograde"?

The imagination of Martians and life on Mars has a long history. As early as 1784, Herschel pointed out in a speech at the Royal Society that Mars is like a replica of the earth, with oceans and land, and Martians face similar situations to earthlings in many ways. A hundred years later, Schiaparelli's photos have inspired a flood of fantasies, from Wells' novel "War of the Worlds", Lao She's novel "Cat City", to the TV comedy "Uncle Martin Mars" that began broadcasting in 1963, in those days, who else on Earth has not heard of Yingyu's distant relatives or mortal enemies?

Fantasize because we are not close enough. In 1965, the Mariner 4 spacecraft flew over the surface of Mars and took the first close-up photo of Mars and sent it back to Earth. Scientists are lost in excitement, especially the outer space biologists who have spent their lives trying to find life on Mars. Mariner 4's observations showed that there was "no rainfall, no ocean, no streams, no ponds", extreme drought, extreme cold, combined with extremely strong radiation and extremely low atmospheric pressure, which made the most optimistic scholars extremely skeptical about the possibility of life on Mars.

Look for the faintest breath in the deepest night

In the midst of this gloom, a young astronomer named Carl Sagan stood up to defend life on Mars, questioning seemingly certain evidence. To further his demonstration, he began building a small laboratory that simulated the Martian environment, proving that microbes could survive in conditions of no oxygen, extreme cold, lack of water and strong radiation. Nine years after Mariner 4's flyby of Mars, he wrote that Mars may not only exist microbes, but also "grand creatures" like turtles, and the number is considerable. This is, of course, nonsense, but a success that stimulates the imagination of the masses. The optimism it conveys is the biggest driving force for the continued development of outer space biology and Mars exploration since then.

In 1980, as a star scientist, Sagan led the production of the blockbuster thirteen-episode TV documentary "Cosmos". Among the millions of American families watching the film is also a child, Sarah Stewart Johnson, who will grow up to be an expert in the search for life in outer space and the author of the book "To Mars".

"To Mars" is not a common popular science work, it is a good blend of history, autobiography and knowledge. Johnson's writing is both vivid and easy to understand, and people with no professional background at all do not seem to have encountered dyslexia.

The cornerstones of life do exist

At the time of writing, Johnson is a veteran of NASA's three missions to Mars. In August 2012, the Curiosity rover landed on Mars. "The entire descent took only seven minutes, almost the same time as the obstetrician pulled my son out of the womb." A few years later, when her children were already able to pick up pinecones and pebbles on mountain roads, Curiosity began drilling mudstone on Mars, eventually finding six elements of carbon, hydrogen, oxygen, nitrogen, phosphorus and sulfur needed for life, as well as certain organic molecules. The discovery "quels one of the longest-standing mysteries about Mars: the building blocks of life do exist."

The discoveries made by Huygens, Schiaparelli and Lowell hundreds of years ago are still relevant. Not only was water once widespread on Mars, it may be so now. In recent years, scientists have increasingly believed that beyond surface and near-surface ice, lakes and oceans may lie beneath its arid, dead ground.

The vast expanse of water stimulates human desire. Our interest in Mars is growing, and many countries and companies are urgently embarking on new expeditions. In February 2021, the U.S. Perseverance rover landed on Mars, and three months later, China's Zhurong also landed on the Utopia Plain. At least one goal in their mission is the same: to determine whether life has ever existed on Mars. That is, to find life from the cornerstones of life. (End)