Repeated imaging of the surface of Mars by orbiting spacecraft over the last two decades has revealed more than one thousand impact sites formed in this time period (Daubar et al., 2013(Daubar et al., , 2019(Daubar et al., , 2022. These observations provide important constraints on the current rate of small impacts on Mars, which are valuable for calibrating crater production models (Daubar et al., 2013;Williams et al., 2014), assessing the impact hazard to spacecraft on Mars, and determining the ratio of primary to secondary crater production rates (Hartmann et al., 2018).Among the known recent impact sites, fewer than half are single craters; the majority are fields of craters, known as crater clusters (Daubar et al., 2013(Daubar et al., , 2019(Daubar et al., , 2022Neidhart et al., 2021). The size and separation of individual craters within these clusters suggest that they are formed due to atmospheric break up of the primary meteoroid into a collection of fragments that separate and strike the ground almost simultaneously (Artemieva & Shuvalov, 2001;Popova et al., 2003Popova et al., , 2007. The diversity of crater clusters, in terms of the spatial distributions and size-frequency distributions of their craters, provide a unique opportunity to interrogate the processes of atmospheric entry and fragmentation, and potentially constrain properties of the impactor population (Daubar Abstract The current rate of small impacts on Mars is informed by more than one thousand impact sites formed in the last 20 years, detected in images of the martian surface. More than half of these impacts produced a cluster of small craters formed by fragmentation of the meteoroid in the martian atmosphere. The spatial distributions, number and sizes of craters in these clusters provide valuable constraints on the properties of the impacting meteoroid population as well as the meteoroid fragmentation process. In this paper, we use a recently compiled database of crater cluster observations to calibrate a model of meteoroid fragmentation in Mars' atmosphere and constrain key model parameters, including the lift coefficient and fragment separation velocity, as well as meteoroid property distributions. The model distribution of dynamic meteoroid strength that produces the best match to observations has a minimum strength of 10-90 kPa, a maximum strength of 3-6 MPa and a median strength of 0.2-0.5 MPa. An important feature of the model is that individual fragmentation events are able to produce fragments with a wide range of dynamic strengths as much as 10 times stronger or weaker than the parent fragment. The calibrated model suggests that the rate of small impacts on Mars is 1.5-4 times higher than recent observation-based estimates. It also shows how impactor properties relevant to seismic wave generation, such as the total impact momentum, can be inferred from cluster characteristics.Plain Language Summary Over a thousand meteorite impacts have been detected in spacecraft images of the surface of Mars in the last two decades. In more t...

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