McLaren's Jenson Button set the pace in Turkish Grand Prix practice while Formula One world champion Sebastian Vettel crashed in the morning and missed the entire second session.
Vettel, the championship leader after winning two of the first three races, gave his Red Bull mechanics plenty of extra work after spinning into the barriers at the rain-soaked Istanbul Park circuit.
The 23-year-old German, who has been on pole position for the past four races, spun at the exit of the challenging triple apex turn eight.
The session was red flagged with 27 minutes remaining, with marshals clearing mud off the track while the battered Red Bull was hoisted onto a flatbed truck and brought back to the pitlane.
The damage was extensive and Vettel was a mere spectator in the afternoon when the sun made a weak appearance and temperatures rose notably.
He will now go into the weekend with no dry weather mileage under his belt.
Button, winner in Turkey with Brawn in his 2009 championship year, was fastest in one minute 26.456 seconds at the front of a quartet of Mercedes-powered cars.
Mercedes' Nico Rosberg was second on the timing screens, ahead of McLaren's 2010 race winner Lewis Hamilton and Rosberg's team-mate Michael Schumacher.
Red Bull's Australian Mark Webber, on pole in Istanbul last year, was fifth.