The Australians are used to winning their share of gold medals at the Olympics, having taken home no fewer than 14 over the last three Games.
They had only two, however, going into Tuesday's events around the Olympics and they managed to double that total thanks to a sprint cycling triumph from Anna Meares and the hurdling title by Pearson.
Pearson, the defending world champion and an Olympic silver medalist in the event four years ago, got off to a tremendous start and held on against fast-charging Dawn Harper. Pearson's time of 12.35 was an Olympic record while Harper finished just 0.02 of a second behind.
Kellie Wells of the United States was third in 12.48 followed by another American, Lolo Jones, in 12.58.
The second-place finish by Harper was one of three for Americans during the evening of track and field.
Erik Kynard of the United States finished second to Russian Ivan Ukhov in the high jump and American Leonel Manzano sprinted down the stretch to pass a host of runners and claim the silver medal in the 1,500-meter run behind Taoufik Makhloufi of Algeria.
The other gold medal event on Tuesday, the men's discus, was won by Germany's Robert Harting over Ehsan Hadadi of Iran.
Harting, who finished fourth in the discus at the 2008 Olympics, has captured the last two world championship titles and has lost an event since August, 2010.
There were no surprises in qualifying for the men's and women's 200-meter dash.
Defending champion Usain Bolt safely made it through the heats while the women's final was set with some tremendous semifinal performances.
Americans Carmelita Jeter, Allyson Felix and Sanya Richards-Ross all ran quicker than 22.50, but they will have to contend with two-time defending Olympic champion Veronica Campbell-Brown of Jamaica.
The early qualifying Tuesday also saw the departure of star Chinese hurdler Liu Xiang, winner of the 110-meter event in Athens eight years ago.
He had to miss the 2008 Games due to an Achilles tendon injury and in his return to the Olympics Tuesday he hit the first hurdle in his qualifying heats.
Liu fell hard and injured his right ankle. He finally got up and hopped into the tunnel that leads away from the stadium.
Suddenly he decided he did not want to leave the Olympics that way so he turned and hopped the entire distance of the track to the finish line. His right foot never touched the ground as he made his way in large jumps, the crowd roaring in support of him.
He was finally assisted by two fellow competitors and left Olympic Stadium in a wheelchair.
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