Mercedes reasserted their authority over Ferrari in Friday's opening practice session for the 2015 Formula 1 Chinese Grand Prix, with world champion Lewis Hamilton heading team mate Nico Rosberg by half a second in Shanghai.
The scarlet cars of Sebastian Vettel and Kimi Raikkonen were a second off the leading pace at the end of the 90 minutes, with Sauber's Felipe Nasr and Red Bull's Daniel Ricciardo the only other men able to get within two seconds of Hamilton's time.
Reigning GP2 champion Jolyon Palmer, meanwhile, enjoyed a positive practice debut with Lotus, finishing 15th despite an early spin, while Marussia got both cars on track as they overcame the technical problems that prevented Will Stevens racing at the last round in Malaysia.
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It had all looked very different at the halfway point of the session, when Rosberg sat atop the timesheet and Hamilton languished in 20th. It took the Briton just one flying lap to take the initiative however, as a 1m 39.033s deposed Rosberg and elevated him to top spot.
Rosberg's 1m 39.574s left him 0.541s in arrears, while Malaysian victor Vettel lagged 1.124s behind the outright pace with 1m 40.157s. Raikkonen was fourth fastest on 1m 40.661s, confirming that Ferrari remain Mercedes' closest challengers. The gap was sizeable, but Ferrari could be more of a threat over long runs - which means all eyes will be on the two teams' race simulations in FP2.
The session itself was marked by several off-track moments and lurid lock-ups as the surface temperature climbed from an initial 26 degrees Celsius to 34 – Hamilton, Rosberg, Vettel, Palmer, his Lotus team mate Pastor Maldonado, Toro Rosso duo Carlos Sainz and Max Verstappen, and Sauber's Marcus Ericsson all explored the available grip and exceeded it, sometimes quite spectacularly, while Felipe Massa spun his Williams after running too deep into Turn 14.
With a differential that worked the way he wanted it to, Nasr put his Sauber fifth after a late improvement to 1m 41.012s. Behind the Brazilian, the Red Bulls squeaked ahead of Sainz's Toro Rosso, with 1m 41.029s for Ricciardo and 1m 41.097s for Daniil Kvyat, compared to Sainz's 1m 41.112s.
Williams could only manage ninth and 10th through Valtteri Bottas and Massa, who were split by just 0.001s on 1m 41.303s and 1m 41.304s respectively. Maldonado and Verstappen were in the same bracket with 1m 41.335s and 1m 41.575s apiece, followed by an encouraged Jenson Button on 1m 41.845s for McLaren on a track where the MP4-30 wasn't expected to shine.
Ericsson was 14th fastest in the second Sauber on 1m 41.918s, ahead of Palmer on 1m 41.967s. The Force Indias then sandwiched Fernando Alonso's McLaren in 16th to 18th places: Perez lapped in 1m 42.141s, Alonso in 1m 42.161s, and Hulkenberg 1m 42.184s.
Marussia occupied the final two spots, as Stevens posted 1m 45.379s and Roberto Merhi 1m 46.443s - the latter being just outside the 107 percent mark.
