On January 7, 1998, approximately 1150 central standard time, a Mooney M20K airplane, N231DS, registered to and operated by the pilot, impacted the ground following an uncontrolled descent approximately 8 miles northwest of Vernon, Texas. The aircraft was destroyed by impact forces and both occupants, the commercial rated pilot and 1 passenger, were fatally injured. An Instrument Flight Rules (IFR) flight plan was filed and instrument meteorological conditions prevailed in the vicinity of the accident. The Title 14 CFR Part 91 personal cross country flight had originated from San Marcos Municipal Airport, San Marcos, Texas, approximately 1000 and was en route to Garden City, Kansas, for a scheduled refueling stop. The aircraft's intended final destination was Andover, Minnesota. The aircraft's cruising altitude en route from San Marcos was 12,000 feet MSL as identified by positive radar returns from Fort Worth Center. Approximately 1145 the pilot requested a descent to 10,000 feet and was given the clearance to descend by Center. After the pilot acknowledged the clearance, both radar returns, and voice communications from the aircraft were lost. The last reported radar position of the aircraft was near the Hobart 193 degree radial at 40 nautical miles. Immediately after the lost contact, Fort Worth center issued an ALNOT (missing aircraft) message. The ALNOT remained in effect until aircraft wreckage, identified as N231DS, was found by a search and rescue helicopter. Several aural witnesses, located about 1 1/2 miles from the fog obscured accident site, reported hearing a very loud engine noise followed by silence at about 1150. Several people living in the vicinity of the accident reported the weather to be foggy, with freezing rain, ice pellets, and low clouds. The aircraft was within the boundaries of a current AIRMET which cited rime icing in clouds below 8,000 feet. No distress calls were heard from the aircraft.