The image above shows a fresh crater on Mars surrounded by a blanket of ejected material; as impacts on Mars go, this particular example is very young, having occurred sometime between January 2014 and August 2016. Nonetheless, impacts like this have been shown to contribute to the total mass of organic material on Mars.
According to an article published in the scientific journal Icarus by a group of researchers from the SRON Netherlands Institute for Space Research, it appears that between 30% and 33% of the total mass of organic material on Mars is being deposited by comets and asteroids during impact events, with the balance coming from ordinary interplanetary dust particles.
According to the article and other sources, the research program was based on the discovery of organic material by the Mars rover Curiosity in 2015, with the work having been carried out by an international team of researchers who had constructed a theoretical model of the solar system that included several hundred thousand comets and asteroids. Using the Peregrine supercomputer at the University of Groningen, the researchers ran the simulation for several weeks, during which time thousands of theoretical comets and asteroids rained down on a theoretical Mars.
The result was illuminating, and revealed that comets provide about 13 tons of carbon to Mars per year, while asteroids deliver about 50 tons of carbon per year. However, while it might be tempting to conclude that since at least some of the ingredients of life, water and organics are present on Mars that there is (or was) a reasonable opportunity for life to have emerged on the Red Planet, it must be remembered that organic compounds have a very short life expectancy on Mars.
The fact is that conditions on Mars’ surface are not conducive to life, due to the high levels of solar radiation at the surface. Moreover, life as we know it requires more than water and a cocktail of organic compounds to take hold, and one missing ingredient from Mars is the required differences between concentrations of dissolved salts and minerals that can be converted into useful biological energy.
Therefore, while the discovery that cometary and other impacts have and continue to contribute to the mass of organic material on Mars is somewhat news worthy, what is more interesting is the fact that organic molecules have been known to exist in deep space for decades, and that more organic compounds are being discovered in deep space almost on a weekly basis.
Thus, it is hardly surprising that at least some of these compounds were originally present in the molecular cloud that condensed to form the solar system, which prompted one commentator, Dr Ben Libberton, a microbiologist at the MAX IV Laboratory in Lund, Sweden, to state that the fact “organic material on Mars can be explained by asteroid strikes could be interpreted as a little disappointing.”
In translation, this means that the discovery is basically a non-event. Since many organic compounds and molecules existed long before the solar system’s formation, it was inevitable that some of this material would have been incorporated into both comets and asteroids, which would have collided with Mars in unavoidable collisions.
More to the point, though, and given the fact that organics do not last long in the Martian atmosphere, the large number of impacts that afflicted Mars during the Great Bombardment era would likely have precluded life from taking a hold there. This means that if life did take hold on Mars, it must have done so comparatively recently, which seems unlikely given the long time it has taken even simple bacterial life to emerge on Earth, where conditions conducive to life were vastly more favorable than they had ever been on Mars.