Jenson Button led a McLaren one-two in the first free practice session of the 2012 Formula 1 season in Melbourne.
Damp conditions early on meant relatively little serious running until the final half an hour, with Button going quickest by 0.245 seconds over team-mate Lewis Hamilton.
Michael Schumacher was third for Mercedes, followed by Fernando Alonso (Ferrari) and home hero Mark Webber (Red Bull).
World champion Sebastian Vettel was a quiet 11th in the second Red Bull.
Toro Rosso's Jean-Eric Vergne had the honour of leading the field out for the first time in an official session in 2012, and the Frenchman and team-mate Daniel Ricciardo had the track largely to themselves at first - choosing to rack up laps while the circuit was still drying, whereas most waited in the pits until conditions improved.
It was Ricciardo who duly logged the season's first flying lap with a 1m47.448s after 20 minutes.
Nearly an hour passed before the Albert Park circuit was in good enough shape for slick tyres. Sauber's Kamui Kobayashi - who by that time was the fastest man on intermediates - led the move to dry tyres and blew his previous benchmark away by just over five seconds.
Webber then deposed Kobayashi, who grabbed the top spot back again, but only momentarily before Schumacher began a long stint in first place, which lasted until Button put in his session-topping 1m27.560s with nine minutes to go.
Hamilton then joined his team-mate at the front with a lap 0.245s slower in the closing moments, pushing Schumacher back to third.
Alonso escaped a massive slide at the final corner on his last lap to take fourth, but his Ferrari team-mate Felipe Massa ended the morning in the gravel after putting a wheel on the grass under braking for Turn 9 with 13 minutes to go, sending the Brazilian spinning.
Nico Rosberg completed the top six for Mercedes, followed by Ricciardo, Pastor Maldonado's Williams, Kimi Raikkonen's Lotus and Kobayashi. Raikkonen only got out in the final few minutes after a long pause in the Lotus garage having his steering rack changed.
HRT endured what has become its traditional very tough start to an F1 season with neither car setting a flying lap. Pedro de la Rosa's machine was not ready in time to leave the pits during the session, while rising engine temperatures led to Narain Karthikeyan's car cutting out on the backstretch after 32 minutes.
Pos Driver Team Time Laps 1. Jenson Button McLaren-Mercedes 1m27.560s 11 2. Lewis Hamilton McLaren-Mercedes 1m27.805s + 0.245 14 3. Michael Schumacher Mercedes 1m28.235s + 0.675 17 4. Fernando Alonso Ferrari 1m28.360s + 0.800 21 5. Mark Webber Red Bull-Renault 1m28.467s + 0.907 21 6. Nico Rosberg Mercedes 1m28.683s + 1.123 22 7. Daniel Ricciardo Toro Rosso-Ferrari 1m28.908s + 1.348 23 8. Pastor Maldonado Williams-Renault 1m29.415s + 1.855 16 9. Kimi Raikkonen Lotus-Renault 1m29.565s + 2.005 8 10. Kamui Kobayashi Sauber-Ferrari 1m29.722s + 2.162 26 11. Sebastian Vettel Red Bull-Renault 1m29.790s + 2.230 21 12. Nico Hulkenberg Force India-Mercedes 1m29.865s + 2.305 17 13. Paul di Resta Force India-Mercedes 1m29.881s + 2.321 18 14. Bruno Senna Williams-Renault 1m29.953s + 2.393 21 15. Sergio Perez Sauber-Ferrari 1m30.124s + 2.564 22 16. Romain Grosjean Lotus-Renault 1m30.515s + 2.955 16 17. Heikki Kovalainen Caterham-Renault 1m30.586s + 3.026 16 18. Felipe Massa Ferrari 1m30.743s + 3.183 11 19. Jean-Eric Vergne Toro Rosso-Ferrari 1m31.178s + 3.618 17 20. Vitaly Petrov Caterham-Renault 1m31.983s + 4.423 8 21. Timo Glock Marussia-Cosworth 1m34.730s + 7.170 8 22. Charles Pic Marussia-Cosworth 1m40.256s + 12.696 11 23. Narain Karthikeyan HRT-Cosworth no time 3 24. Pedro de la Rosa HRT-Cosworth no time 0 All Timing Unofficial
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