Hamilton leads Mercedes one-two in practice
Mercedes driver Lewis Hamilton speeds out of the pits during the first practice session at the Australian Grand Prix in Melbourne on March 14, 2014 - by William West
Former Formula One world champion Hamilton overcame mechnical problems in the first session to top the charts just ahead of his German team-mate Rosberg.
Rival drivers have tipped the Mercedes pair to fight it out for Sunday's race, given the team's superior pre-season testing and adjustment to sweeping technical changes.
A return to turbocharged engines, lower fuel loads, gearbox changes and new energy recovery systems are among significant rule changes for the new season.
Hamilton put in a scorching lap on soft tyres to post a best time of one minute 29.625, some 0.157secs ahead of Rosberg (1:29.782).
The Mercedes duo were the only drivers to go below 1:30, demonstrating an early edge over the rest of the field ahead of Saturday's qualifying for grid positions.
Ferrari's Fernando Alonso backed up from topping first practice with the third best time of 1:30.132, just over a half-second slower than Hamilton.
Four-time world champion Sebastian Vettel was fourth quickest in his Red Bull in 1:30.381, but a significant 0.756secs down on Hamilton.
It wasn't so enjoyable earlier in the day for Hamilton, the 2008 world champion, who came to a halt on his installation lap in the first practice session.
Hamilton had an inauspicious start to his season when his Mercedes stopped on its first lap, with smoke coming from the rear of the car.
The Briton got out of the car, which was towed back to the team garage in an initial setback for the Mercedes team in its first run on the Albert Park circuit.
Hamilton also had the indignity of having his pass checked by security as he returned to the paddock still wearing his race helmet.
Mercedes reported that an oil pressure alarm had led to a precautionary shutdown in his car.
McLaren's former world champion Jenson Button had a promising day, featuring high in both practice sessions and clocking the fifth best time of 1:30.510 in the second run.
Vettel's new Australian team-mate Daniel Ricciardo got in plenty of laps in the second Red Bull car and finished sixth.
Alonso's new Ferrari stablemate Kimi Raikkonen was seventh, ahead of Finland's Valtteri Bottas in a Williams and Danish debutant Kevin Magnussen driving a McLaren.
Japan's Kamui Kobayashi in a Caterham missed the entire second practice session after experiencing problems in the first session, meaning his whole day was wiped out.
Pastor Maldonado also sat out the second session after problems with his Lotus, while Caterham's Marcus Ericsson only managed one lap in second practice.
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