Official Image

Debain

login user: user  
login password: milkv

Download from Github

Images introduction:

Mars CM eMMC version image

mars-cm_debian-desktop_sdk-v*_cm4-io-board_emmc_v*.img.zip

Mars CM Lite (SD card) version image

mars-cm_debian-desktop_sdk-v*_cm4-io-board_sdcard_v*.img.zip