Casey Stoner was quickest in second practice at Aragon, as rain hampered the teams' efforts to set their bikes up on the new circuit.
Conditions varied from drizzle to heavier rain during the session - which was 45 minutes long rather than the usual hour as part of the schedule rejig to accommodate the return of Friday morning practice for this weekend - without ever really improving. Lap times in the closing minutes were only 2-3 seconds quicker than at the start.
Jorge Lorenzo looked set to top the session at the chequered flag, but Ducati's Casey Stoner produced a 2m01.710s lap with his very last effort to beat the Yamaha by half a second.
Stoner's team-mate Nicky Hayden kept up his strong form to take third ahead of Valentino Rossi on the second Yamaha.
Marco Melandri was the most notable underdog in the lead group, the Italian making the most of the weather to put his Gresini Honda fifth.
Morning pacesetter Dani Pedrosa (Honda) had led the way in the first half of the session, but did not set any quick times in the latter part, when the track was slightly less wet, and therefore fell to 13th.
Pos Rider Team Time Gap
1. Casey Stoner Ducati 2m01.710s
2. Jorge Lorenzo Yamaha 2m02.278s + 0.568s
3. Nicky Hayden Ducati 2m02.411s + 0.701s
4. Valentino Rossi Yamaha 2m02.878s + 1.168s
5. Marco Melandri Gresini Honda 2m03.146s + 1.436s
6. Andrea Dovizioso Honda 2m03.754s + 2.044s
7. Randy de Puniet LCR Honda 2m03.801s + 2.091s
8. Ben Spies Tech 3 Yamaha 2m03.874s + 2.164s
9. Hector Barbera Aspar Ducati 2m04.063s + 2.353s
10. Marco Simoncelli Gresini Honda 2m04.151s + 2.441s
11. Colin Edwards Tech 3 Yamaha 2m04.868s + 3.158s
12. Alvaro Bautista Suzuki 2m05.170s + 3.460s
13. Dani Pedrosa Honda 2m05.394s + 3.684s
14. Mika Kallio Pramac Ducati 2m06.257s + 4.547s
15. Aleix Espargaro Pramac Ducati 2m07.133s + 5.423s
16. Hiroshi Aoyama Interwetten Honda 2m07.632s + 5.922s