In a week, if the landing goes as planned, NASA's Mars Curiosity rover will be looking for signs of methane and other organic compounds in the atmosphere and the soil, which could turn up new clues in the search for life there.
If we found life on another planet, the discovery would go a long way toward answering the deepest open questions in biology: How did life originate, how widespread is life in the universe, and are there alternative recipes for life?
There’s no obvious sign of life on any of our neighbors in the solar system. But desolate, frozen Mars keeps calling scientists back. In the Martian landscape, geologists see dry riverbeds and flood plains that hint at a warmer past that just might have allowed life to originate.
All life on Earth appears to be related, using DNA and RNA molecules to pass down assembly instructions and other information. We share stretches of this genetic code with bacteria, yeast and amoebas.
But if life originated on Mars, it might use a completely different way of storing and transmitting information. And so, if the Mars Science Laboratory lands safely next week, instruments will begin to analyze the soil, air and rocks for life, past or present.
The warm period was early in the history of the solar system — it looks to have begun freezing up by 3 billion years ago. The Martian atmosphere today is too thin to hold in much heat, but perhaps greenhouse gases once blanketed the planet and were later lost.