Astrogeology is yet another field that is benefitting from both data from advanced imaging of planets, moons, asteroids, and comets in our solar system, and machine learning from computer science. Researchers knew that there were hundreds of thousands of craters on Mars with diameters larger than 1 kilometer. All these craters were determined by humans. However, having a human identify craters quickly runs into a barrier – the crater size. The accepted hypothesis, that the rate of impacts on planetary surfaces follows a power law, means that the number of smaller craters is exponentially higher. Enter the pursuit of a computational means for counting. Such a capability now exists.
Benedix et al.  present the results of computer crater selection that have been validated against current manual databases. The new algorithm is shown to successfully count craters down to 10 pixels diameter on any number of high‐resolution images. This means, for the first time, an automated crater counting tool can deliver geologically meaningful relative ages as well as counts for craters.
If samples are obtained (cf. the Apollo moon missions), then a radioisotope age from a specific crater provides a calibration, i.e. an absolute chronometer. Thus, we await Mars samples. And where next? The authors indicate that “planets and other bodies in our solar system … provide a template for untangling planet formation and evolution” but more widely. Indeed, what are the desirable neighborhoods of space for life elsewhere?
Citation: Benedix, G. K., Lagain, A., Chai, K., Meka, S., Anderson, S., Norman, C., et al. . Deriving surface ages on Mars using automated crater counting. Earth and Space Science, 7, e2019EA001005. https://doi.org/10.1029/2019EA001005
—Peter Fox, Editor in Chief, Earth and Space Science