The Mars Tragedy (Mars Disaster, Great Mars Tragedy of '25) was a terraforming disaster that occurred on 13 September 2125 SEY. Late in the initial terraforming of Mars (Sol IV), an error in the atmospheric processors caused the newly generated oxygen/nitrogen atmosphere to catastrophically dissipate, resulting in the sudden suffocation of 4,876 people.
The public outcry against terraforming following the tragedy halted development of the technology for twenty years. In the mid-2150s, better safety protocols and more precise atmospheric processing standards were made standard thanks to data gathered from this event, and Mars was successfully terraformed.