Ahead of today's sole free practice session, the air temperature is 27 degrees C, while the track temperature is 38 degrees.

Only Ferrari and McLaren are running KERS this weekend, while the tyre options are hard and soft. It was clear that that the softs are degrading quite quickly, particularly on the Ferraris, and while there was little pace difference, the softs seem to be at their best when it's cooler.

A bit of a topsy-turvy day yesterday, which didn't really give a very clear picture of who is where here, however, the true running order should become a little more apparent over the course of the next hour.

Within minutes of the lights going green, all but Raikkonen and Barrichello have been out for an installation lap.

Nine minutes into the session, Massa is the first driver to go out for a second run, the Brazilian posting a 29.036. Shortly after, Trulli goes second, Glock third and Sutil fourth.

Massa improves to 28.592, almost a second quicker than anything he did yesterday. Indeed, all the times are up on yesterday.

Kubica goes fourth, the Pole hoping that the raft of updates on the F1.09, including a split diffuser, will lead to a major step forward. Elsewhere, Heidfeld goes quickest in the first sector, finally crossing the line at 29.280 to go fourth.

A 29.067 sees Button go second, as teammate Barrichello improves to sixth. Having gone quickest in the final sector, Kovalainen goes fifth.

Barrichello goes quickest with a 28.514 as Rosberg goes third. On his next lap the German goes quickest in the first sector, finally crossing the line at 28.364 to go quickest. The top 16 are covered by just 1.003s.

Hamilton goes fourth with a 28.563, as Kovalainen slips down to fourteenth.

At half-time, it's: Rosberg, Barrichello, Button, Massa, Hamilton, Nakajima, Raikkonen, Webber, Heidfeld and Trulli.

Massa improves with a 28.253, the Brazilian determined to make it three successive wins here in Istanbul. Clearly, a podium finish isn't an option for the Ferrari driver and 2008 championship runner-up.

As Piquet (softs) goes fourth, Alonso remains at the bottom of the timesheets along with former teammate Fisichella. At the top of the timesheets Massa raises the benchmark with a 27.983.

Replay shows Alonso running wide before heading straight back to the pits. Elsewhere, Raikkonen improves to third, as Hamilton is told that the best time to use his KERS is when he exits Turn 9.

Nakajima makes it a Williams 3-4 when he posts 28.364, exactly the same time as his German teammate.

Vettel complains that due to understeer he is really struggling. In fact, he doesn't appear to be alone.

Massa (softs) goes quickest in the final sector but fails to improve overall. The Brazilian is the only man on track.

With seven minutes remaining, Rosberg heads down the pitlane to join Massa. More and more cars head out of their garages, all appear to be on softs, the final assault gets underway.

Button improves to third (28.360), to make it a Brawn 2-3. However, moment later Glock goes second, only to spin at the beginning of his next lap.

There are no purples on the timing screen, but plenty of greens, however, there are no major improvements, the softs appearing to be only good for two or three really hot laps.

That said, Trulli goes second and Kubica fourth, however, still no purple sectors.

A late improvement sees Nakajima improve to fourth, as Alonso remains nineteenth, albeit just 1.278s off the pace.

Therefore, Massa is quickest, ahead of Trulli, Glock, Nakajima, Kubica, Barrichello, Button, Rosberg, Raikkonen and Vettel.

Piquet was eleventh, ahead of Hamilton, Webber, Heidfeld, Kovalainen, Sutil, Bourdais, Buemi, Alonso and Fisichella.