Sky Matters: Why are there no Martians and no cities on Mars?

Niall Smith ponders life on Mars

Undated handout artist impression issued by NASA of NASA's Perseverance rover landing safely on Mars. Nasa's Mars Perseverance rover will land on the red planet on Thursday to begin its search for traces of life. Issue date: Thursday February 18, 2021.

February was a red-letter month for the Red Planet as three spacecraft from three different countries successfully traversed the immense void between our two worlds to reach their destination. I watched with excitement as NASA’s Perseverance Rover sent back a low-resolution black-and-white image moments after it landed on an ancient lake bed called Jezero Crater. It reminded me of a day in 1969 when Apollo 11 touched down on the lunar surface. Unlike in the days of Apollo, the days of Perseverance are focused purely on the science, on the search for evidence that life may once have existed, perhaps prospered, in a lake on a planet that is not Earth. Some 3.5 billion years ago Mars had an atmosphere that wrapped around it like a blanket, trapping the Sun’s heat and generating temperatures where liquid water could exist. For millions of years the conditions that we know are necessary for life on Earth existed on Mars. 

For millions of years, the building blocks of life swashed around in the waters of Jezero Crater lake. So maybe, just maybe, those building blocks managed to convert inanimate into animate. As a friend of mine remarked many years ago, this is the “giant leap” (to borrow an Apollo 11 phrase), but one that is by no means certain. The evolution that follows, by contrast, seems almost inevitable. If life did get a foothold on Mars, why do we not see this inevitable evolution today? Why no Martians, no Mars cities (and no evil death rays … which is undoubtably a good thing)?