When the Perseverance rover takes off from Cape Canaveral in Florida as scheduled on Thursday it will be Nasa’s first mission to the surface of the red planet with the primary goal of finding signs of past life.
For astrobiologists, this search for life beyond Earth can be compared to a game of darts. Hitting the bullseye would mean finding “life as we know it”. In other words, life based on a biology analogous to that found on Earth. But as any darts player knows, the bullseye is a small target, hard to hit and not even the highest scoring area on the board.
That’s why new research supported by Nasa’s astrobiology programme has developed a novel and broader definition of life – a definition that encapsulates life on Earth but also the possibility of “life not as we know it” elsewhere on the board. They call it lyfe.
There is no universally agreed definition of life. But Nasa has a good working description: “a self sustaining chemical system capable of Darwinian evolution”.
All living organisms on Earth take in energy, use and change it, and then release it in a less useful form as waste. All use the same 20 amino acids to make proteins. All use RNA and DNA molecules to store genetic information.
Weighing just over a tonne, the Perseverance rover will land on the Jezero crater, an area once thought to have been flooded with water and therefore a promising candidate for signs of past such life.
Accompanied by a drone helicopter to scout locations, Perseverance will identify, collect and store samples of rock and soil. These samples will then be picked up and returned to Earth by a future mission. Scientists will be looking for certain biosignatures that could indicate evidence of past life. If life as we know it ever existed on Mars, there is a good chance it will eventually be discovered by Perseverance.
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