Schumacher makes test debut for Mercedes

Valencia: Seven-times world champion Michael Schumacher returned to the Formula One racetrack on Monday with his first test for Mercedes since coming out of retirement.

The 41-year-old German, who last raced for Ferrari in 2006, took over from team mate Nico Rosberg with an hour and a half remaining of the first test session of the new season at Valencia's Ricardo Tormo circuit.

With photographers and reporters crowding the pitlane, Schumacher guided the silver W01 car out onto the track where former Ferrari team mate Felipe Massa had already racked up more than 60 laps.

Smiling Button and Hamilton unveil new McLaren

The Brazilian, clearly back up to speed in the new Ferrari F10, was returning to competitive action six months after suffering life-threatening head injuries in Hungarian Grand Prix qualifying.

Within minutes Schumacher was already lapping faster than Brazilian Rubens Barrichello, another former Ferrari team mate, in the Williams.

The lap times meant little however, with refuelling banned this season and cars testing with varying fuel loads and specifications.

Rosberg, who completed 39 laps, said first impressions of the new car, an evolution of the Brawn that won both of last year's championships before the team was taken over by Mercedes, were very positive.

"It felt great, although difficult to compare because there are so many things different with the fuel and tyres," added the 24-year-old, who has joined Mercedes after four years at Williams.

"To have him (Schumacher) here is fantastic," he said. "It has given me a little bit extra motivation I must say, from my point of view. Just that little touch extra."

Completing a day of comebacks, veteran Spaniard Pedro de la Rosa made his first appearance in three years as a fully-fledged racing driver when he tested the new Sauber.

Britain's Gary Paffett gave the sleek-looking new McLaren its test debut, before world champions Jenson Button and Lewis Hamilton get their hands on it later in the week.

Poland's Robert Kubica made his Renault debut, after moving from BMW-Sauber while Switzerland's Sebastien Buemi gave the new Toro Rosso a first run.

The STR5 is the first car Red Bull-owned Toro Rosso have built and designed separately from the Red Bull Racing team, in line with new regulations banning "customer cars".

Formula One 2010: The King returns

"Making predictions...is a dangerous trap but if pushed, I would say we must aim to finish in the top eight in the constructors' championship," said team boss Franz Tost.

None of the four completely new teams are attending the Valencia test, with Virgin Racing due to unveil their new car online on Wednesday and Lotus firing up their car's engine for the first time next Friday before a launch on February 12.

Spanish-based Campos Meta have yet to name a partner to Brazilian Bruno Senna while the North Carolina-based US F1 team plan to carry out their first tests in Alabama.

Red Bull, last year's overall runners-up, are also missing the opening test to give themselves more time to push development as are Force India.