It seems to be coming together very nicely for defending World Champion Sebastian Vettel.

The young German was comfortably the fastest driver on the first day of the second multi-team test session, ahead of the 2012 Formula 1 World Championship. The Red Bull Racing driver was utterly dominant in last year's title race and reckons he has the machinery to ensure that dominance continues.

The opening day of the second test session of the year saw 11 of the 12 teams competing in this year's championships on track; the only team missing was HRT.

The highlight of the day was also the track debut for the Mercedes team's new car, the W03, which was unveiled on Tuesday. Their driver for the day, seven-time World Champion Michael Schumacher, completed 51 laps before a hydraulic problem intervened.

"My initial feelings with our new car are certainly good," said Schumacher to Formula1.com, adding, "I'm happy with the different evaluations that we have done over the last week, but obviously with the rule changes, we won't know more until later. It's certainly an improvement."

Meanwhile, also on track was Ferrari's Fernando Alonso. The marquee Italian team had a miserable 2011 campaign and will be hoping the F2012 can get them back up to speed. Alonso completed 75 laps and focused primarily on development work.

Testing continues on Wednesday.

Unofficial Times from Tuesday's Session:

1. Sebastian Vettel, Red Bull - 1:23.265 (79 Laps)

2. Nico Hulkenberg, Force India - 1:23.440 (97 Laps)

3. Lewis Hamilton, McLaren - 1:23.590 (114 Laps)

4. Daniel Ricciardo, Toro Rosso - 1:23.618 (76 Laps)

5. Fernando Alonso, Ferrari - 1:24.100 (75 Laps)

6. Michael Schumacher, Mercedes - 1:24.150 (51 Laps)

7. Sergio Perez, Sauber - 1:24.219 (66 Laps)

8. Bruno Senna, Williams - 1:25.711 (97 Laps)

9. Heikki Kovalainen, Caterham - 1:26.035 (31 Laps)

10. Romain Grosjean, Lotus - 1: 26.809 (7 Laps)

11. Charles Pic, Marussia* - 1:28.026 (121 Laps)
* 2011 car; team formerly called Virgin Racing Formula One Team

Meanwhile, start the slideshow to see all the action from the Circuit de Catalunya in Barcelona, Spain...