Asteroid impacts on Mars could have made life possible on this planet: the surface of Mars is littered with impact craters, asteroids contain organic building blocks for life, and the heat released during an impact can lead to a hydrothermal system in the subsurface that can support life for a long time. However, it is not easy to study these systems directly on Mars. That is why Earth scientist Jitse Alsemgeest studied comparable impact craters on Earth, specifically the Vargeão Dome and Vista Alegre impact craters in Brazil, to see what the chemistry and evolution of hydrothermal systems around these types of craters is – and whether this could actually support life on Mars.
Size of hydrothermal systems too limited to support life
Alsemgeest's research shows that the impact-related hydrothermal systems in the Vargeão and Vista Alegre impact crater were probably limited in size, which also limits the possibility of supporting life. In order to support life, there are larger impact craters that provide more heat. Because gravity on Mars is weaker than on Earth, hydrothermal systems in impact craters work differently there - they only become comparable to the systems on Earth when they are about 4 times as large. This means that craters on Mars must be at least 40-50 km in diameter to be able to support life. This excludes about 99.5% of the craters (larger than 1 km) on Mars.
Next step to Mars
The search for life beyond our planet is no easy task. However, Alsemgeest's research makes it possible to search much more specifically for signs of life on Mars, which brings us one step closer to an answer to the question of whether we are alone in the universe. In addition, this research provides perspective: "Mars turns out not to be all that different from Earth. Processes on this planet can also be found on Earth - this gives all the more reason to take the next step for humanity and go to Mars, according to Alsemgeest.
Veins in rocks
Alsemgeest investigated veins in rocks: these are thin mineral bands that are formed by the flow of hot water in a hydrothermal system. The minerals in these veins indicate the temperature and composition of the water when the hydrothermal system was active. In order to determine this, he first collected rocks in Brazil that have these types of veins. He then determined the composition of the minerals with an electron microscope and made a computer model of the hydrothermal system. He eventually adapted this to conditions on Mars to see whether or not impact-related hydrothermal systems on this planet can support life.
Alsemgeest will receive his PhD on September 3, 2024 from the Vrije Universiteit Amsterdam.