SPARTA (Stochastic PArallel Rarefied-gas Time-accurate Analyzer) is a parallel Direct Simuation Monte Carlo (DSMC) solver for performing simulations of low-density gases in 2D or 3D. SPARTA was primarily developed at Sandia National Laboratories, a US Department of Energy (DOE) laboratory. I used SPARTA to simulate 2D flow around cylinders in Martian atmosphere after curating a repository on Martian atmospheric data.
We can see a ray-traced image of a snapshot of the simulation above.