Melbourne: The McLarens of Britons Jenson Button and Lewis Hamilton posted the fastest times as Formula One got back to business with the first two practice sessions for the season-opening Australian Grand Prix on Friday.
Button edged fellow former world champion Lewis Hamilton into second place by 0.245 seconds on the timesheets with a quickest lap of one minute 27.560 seconds in the first session.
A torrential downpour between the two sessions meant the times in second practice were down on the first, with most teams running wet weather tyres for all but the last 15 minutes.
Seven-times champion Michael Schumacher had put Mercedes on top for much of the opening session with the quickest of his 17 laps (1.28.235) to confirm his Mercedes team's promising pre-season testing.
The 43-year-old German, who has yet to get on the podium since his return to the sport two years ago, also registered the fastest time in the second session in 1.29.183.
Fernando Alonso, another of the unprecedented six former world champions in the field, was fourth fastest for Ferrari in 1.28.360 despite a dangerous wobble coming into the home straight on the last of his 21 laps in the morning.
Red Bull's Mark Webber, who will be looking to better his best finish of fifth in his 11th home grand prix, was fifth fastest with his reigning world champion team mate Sebastian Vettel 11th in the first session and 10th in the second.
The 24-year-old German, seeking a third successive world title this year, is unlikely to be too concerned.
With teams using a variety of set-ups and fuel loads in the early practice sessions, little will be read into the relative speed of the leading contenders.
Former champion Kimi Raikkonen, returning this season with Lotus after two years out of the sport, ran just 15 laps over both sessions and recorded the ninth quickest time in the morning of 1.29.565.
Brazilian Felipe Massa is fighting for his drive at Ferrari after a miserable 2011 and had a morning to forget after sliding into the gravel midway through the session and managing just the 18th quickest time.
Toro Rosso's French rookie Jean-Eric Vergne was first out on a track still wet from the morning rain and only the HRT of Pedro de la Rosa failed to get out of the garage during the opening 90 minute session.
The Spaniard did get his car onto the track in the second session but failed to complete a lap.
A third practice session takes place on Saturday before qualifying for Sunday's race.