Astronomie - Mars-Krater im Focus von HIRISE


The discovery of 248 dated impact sites known to have formed within the last few decades allows us to refine the current cratering rate and slope of the production function at Mars. We use a subset of 44 of these new craters that were imaged before and after impact by Mars Reconnaissance Orbiter's Context Camera -- a thoroughly searched data set that minimizes biases from variable image resolutions. We find the current impact rate is 1.65×10-6 craters with an effective diameter ≥ 3.9 meters / km2 / year, with a differential slope (power-law exponent) of -2.45 ± 0.36. This results in model ages that are factors of three to five below the Hartmann (2005) and Neukum et al. (2001)/Ivanov (2001) model production functions where they overlap in diameter. The best-fit production function we measure has a shallower slope than model functions at these sizes, but model function slopes are within the statistical errors. More than half of the impacts in this size range form clusters, which is another reason to use caution when estimating surface ages using craters smaller than ~50 meters in diameter. 
Quelle: NASA