Upper left panel: PMs of the stars in the M 22 region with σ ≤ 1.0 mas yr⁻¹. Higher transparencies represent lower densities of stars. Overplotted in red are the PMs of the stars located in the innermost regions (r ≤ 1.0′) of this GGC. Lower left panel: PMs of the detected variable stars in the field covered by M 22. Those stars selected as cluster members by our kNN classifier are shown according to their variability type: the solid magenta triangles indicate RRab stars, empty magenta triangles are RRc stars, blue squares are Cepheids, green pentagons are eclipsing binaries, and inverted red triangles are unclassified variables. Right panel: J − K_s vs. K_s near-infrared CMD of the stars in the M 22 field. Higher transparencies represent lower densities of stars. Overplotted in yellow are the stars located in the innermost regions (r ≤ 1.0′) of this GGC that were selected as candidates by our kNN classifier. The cluster member variables from the lower left panel are also overplotted. The arrow in the upper left corner shows the selected reddening vector.