QUESTION:
When the Pathfinder lands on Mars it has a parachute that opens when it
reaches a speed of 1500 km/hr.  How was this parachute designed and tested
to open and work effectively in the thin Martian atmosphere? 

ANSWER from Chieck Diarra on November 27, 1996:
The parachute used in this mission is derived from the one used
successfully for the Viking landers. It was manufactured by Pioneer
Aerospace Corporation and has been very severely tested. A mortar is used
to eject the parachute; this will force it to open and be operational in
the shortest time possible.