Like at Earth, disturbances from solar storms affect the space environment as they encounter Mars. The effects of the 28 October 2003 solar superstorm were among the greatest observed by the Mars Global Surveyor spacecraft at Mars to date. The disturbance, defined by an increase in incident solar wind pressure, encountered Mars on 30 October 2003 and persisted for 43 hours. We present the effects of the passage of this high-pressure disturbance and compare the modified Martian space environment to more quiescent times. We find that the horizontal component of magnetic field is increased on the dayside. In addition, the solar wind interaction region is compressed during the disturbance. The solar wind flow has access to lower altitudes than typical, which likely increases mass loss from the Martian atmosphere. Regions of opened magnetic field lines can be closed at 400 km due to the compression of minimagnetospheres, thus altering locations where ionospheric plasma is protected from solar wind scavenging at 400 km altitude.