Ferrari driver Fernando Alonso set the pace in a wet first practice session for the Turkish Grand Prix at Istanbul.
The Spaniard's best lap of 1m38.670s was set on intermediate tyres during a changeable and eventful session that featured a red flag because of an accident involving world champion Sebastian Vettel.
Mercedes drivers Nico Rosberg and Michael Schumacher were second and third fastest ahead of the Renault's of Nick Heidfeld and Vitaly Petrov.
Sauber's Kamui Kobayashi, typically spectacular, was sixth in the Sauber ahead of Felipe Massa, Toro Rosso Friday man Daniel Ricciardo and his team-mate Sebastien Buemi and Force India's Nico Hulkenberg.
The rain offered the first opportunity for the drivers and teams to learn about Pirelli's wet weather tyres in competition conditions, but as usual it was a while before anyone set a realistic time.
Just after half an hour Alonso set the first representative lap of the frontrunners with a 1m40.897s, on his fifth lap on full wet tyres. But already the Spaniard was indicating over the radio that he had already got the best from the Pirelli's grip window.
A couple of minutes later, Nico Rosberg moved the target time down to 1m40.072s - 0.8s faster than Alonso.
Mark Webber emerged from the pits just after halfway through the 90 minute session - the first driver to give the intermediates a try, but his lap was only good enough for tenth and he quickly returned to the pits.
Up to this point the rain had been steady, but light, then with 40 minutes to go it began to fall harder again and Rosberg told his team that aquaplaning was occurring at Turns 2 and 11.
That didn't stop Alonso moving back to the top of the times with a 1m38.670s, and he was on intermediates.
Meanwhile several drivers ignored Rosberg's advice and ran wide at the fast Turn 11 - a list that included Timo Glock, Sebastien Buemi, Schumacher, Felipe Massa and Sebastian Vettel who finally decided to venture on to the track having missed the driest period of running.
Not long after though, the world champion was in the barriers having given them a hefty whack when he ran wide at Turn 8. So hefty in fact that he brought out the red flag for 10 minutes - leaving just 15 minutes to go.
But the track was now thoroughly wet and those that ventured out discovered it had lost a couple of seconds in pace.
Both rookies Pastor Maldonado and Paul di Resta, as well as Schumacher all registered a spin each. Maldonado actually had two incidents - the second of which appeared to damage his car.
McLaren drivers Jenson Button and Lewis Hamilton did not complete any significant running, with the latter not even setting a time.
Pos Driver Team Time Laps
1. Fernando Alonso Ferrari 1m38.670s 13
2. Nico Rosberg Mercedes 1m40.072s + 1.402 14
3. Michael Schumacher Mercedes 1m40.132s + 1.462 18
4. Nick Heidfeld Renault 1m40.338s + 1.668 9
5. Vitaly Petrov Renault 1m40.401s + 1.731 10
6. Kamui Kobayashi Sauber-Ferrari 1m40.421s + 1.751 16
7. Felipe Massa Ferrari 1m40.697s + 2.027 14
8. Daniel Ricciardo Toro Rosso-Ferrari 1m41.094s + 2.424 18
9. Sebastien Buemi Toro Rosso-Ferrari 1m41.178s + 2.508 22
10. Nico Hulkenberg Force India-Mercedes 1m41.347s + 2.677 16
11. Mark Webber Red Bull-Renault 1m42.564s + 3.894 5
12. Pastor Maldonado Williams-Cosworth 1m42.597s + 3.927 7
13. Paul di Resta Force India-Mercedes 1m43.525s + 4.855 11
14. Rubens Barrichello Williams-Cosworth 1m43.913s + 5.243 5
15. Karun Chandhok Lotus-Renault 1m43.986s + 5.316 6
16. Tonio Liuzzi HRT-Cosworth 1m44.787s + 6.117 20
17. Sebastian Vettel Red Bull-Renault 1m44.954s + 6.284 4
18. Timo Glock Virgin-Cosworth 1m45.183s + 6.513 15
19. Jerome D'Ambrosio Virgin-Cosworth 1m45.237s + 6.567 11
20. Narain Karthikeyan HRT-Cosworth 1m48.461s + 9.791 8
21. Jarno Trulli Lotus-Renault 1m51.676s + 13.006 6
22. Sergio Perez Sauber-Ferrari 1m55.791s + 17.121 13
23. Jenson Button McLaren-Mercedes 2m00.666s + 21.996 4
24. Lewis Hamilton McLaren-Mercedes no time 1
All Timing Unofficial