For scientists searching for alien lifeforms, the siren song of Mars is climbing toward a crescendo. Multiple recent observations made by rovers on the red planet could bear the signatures of microbes—a possible indication that Earth is not the only refuge for life in the solar system.

One exciting glimmer was announced earlier this month: NASA’s Curiosity rover observed a mixture of carbon isotopes in the rocks of Gale crater that, if seen on Earth, would be a sign of life. The rover has also witnessed both random and seasonal surges of methane, a gas on Earth that is predominantly produced biologically.

About 2,300 miles away in Jezero crater, NASA’s