hampionship leader Sebastian Vettel crashed heavily at Istanbul's daunting Turn 8 corner during a wet opening practice session ahead of the Turkish Grand Prix.The impact caused significant damage to his RB7 bearing the number 1, and he told his engineers by radio there was "some water on the exit. There was nothing I could do".The incident caused the 90-minute session to be red-flagged with just over 17 minutes to run. Ferrari's Fernando Alonso was able to capitalise on Vettel's crash by topping the timesheets, followed by the Mercedes duo of Nico Rosberg and Michael Schumacher.FLYING DEBRISVettel went way out on a right turn and his car slid left back across the track and into the crash barrier on the other side of the slippery Istanbul Park track.Debris flew off the car and the wheels were skewed. The F1 champion waited for track officials to reach him and his mangled car was towed away. Team members cleared some debris.Vettel is leading the overall standings by 21 points from Britain's Lewis Hamilton after winning two of the opening three races.Drivers struggled throughout the first practice as teeming rain and cool conditions made it hard to take risks.Shortly before Vettel's mishap, seven-times champion Michael Schumacher had to take emergency action himself not to crash, expertly regaining control of his Mercedes after also spinning.First-practice results:1 Fernando Alonso Ferrari 1min38.670 2 Nico Rosberg Mercedes 1min40.072 3 Michael Schumacher Mercedes 1min40.132 4 Nick Heidfeld Renault 1min40.338 5 Vitaly Petrov Renault 1min40.401 6 Kamui Kobayashi Sauber-Ferrari 1min40.421 7 Felipe Massa Ferrari 1min40.697 8 Daniel Ricciardo STR-Ferrari 1min41.094 9 Sebastien Buemi STR-Ferrari 1min41.178 10 Nico Hulkenberg Force India-Mercedes 1min41.347 11 Mark Webber RBR-Renault 1min42.564 12 Pastor Maldonado Williams-Cosworth 1min42.597 13 Paul di Resta Force India-Mercedes 1min43.525 14 Rubens Barrichello Williams-Cosworth 1min43.913 15 Jarno Trulli Lotus-Renault 1min43.986 16 Vitantonio Liuzzi HRT-Cosworth 1min44.787 17 Sebastian Vettel RBR-Renault 1min44.954 18 Timo Glock Virgin-Cosworth 1min45.183 19 Jerome d'Ambrosio Virgin-Cosworth 1min45.237 20 Narain Karthikeyan HRT-Cosworth 1min48.461 21 Karun Chandhok Lotus-Renault 1min51.676 22 Sergio Perez Sauber-Ferrari 1min55.791 23 Jenson Button McLaren-Mercedes 2min00.666 24 Lewis Hamilton McLaren-Mercedes No time For second practice results click here!