Marquez tops Argentina practice
Spanish biker Marc Marquez rides his Honda during the MotoGP free practice of the Argentina Grand Prix at the Termas de Rio Hondo circuit, in Santiago del Estero, Argentina on April 25, 2014 - by Juan Mabromata
The Spanish Honda rider is seeking to make it three wins out of three this season as the world championship returns to Argentina for the first time since 1999.
And the 21-year-old proved a quick learner as he made light of the alien surroundings to top the times by over one second from his teammate Dani Pedrosa.
In third came the Yamaha of Aleix Espargaro, Stefan Bradl (Honda) took fourth with Ducati's Andrea Dovizioso completing the top five.
Former double world champion Jorge Lorenzo had posted the quickest time in first practice but the Yamaha rider plummeted down to ninth overall after the second session.
His first session time of 1min 42.804sec was almost five seconds slower than the one Marquez was to set later.
Marquez is on a three-timer after winning the season-opener in Qatar one month after breaking his leg, doubling up in the Grand Prix of the Americas.
The youngest ever world champion leads the MotoGP standings by 36 points from Pedrosa going in to Sunday's race.
Australia's Jack Miller emerged quickest in Moto3 practice.