It has been two and a half months since Pettersen last played a competitive event but she again showed her grit, recovering from an early bogey in her morning round to record nine birdies including those at her last three holes of the day.
"The first round of the year always anxious to get started," said Pettersen. "I had a very good warm up. It took me a little while to get really comfortable, to trust what I've been working on but figuring out that the trust is stronger than the rest, so I had a lot of great shots. I also must say I feel like I left a lot of shots out there. I mean, I three putted a couple of greens, stupid three putts really.
"But also I felt like I played good and gave myself a lot of good chances, putted, for the most part, well. It was a little bit of a mixture but 66 opening round, I'm very, very happy."
Pettersen can take over as the world number one if she finishes first or second this week although her response to a question on that issue was a little strange although perhaps tells the story of why she is so good.
"I really just want to see how good I can be. I know I'm good. If I play like I did today and trust my swing and trust what I'm working on, I just want to see how far I can get and I don't really measure myself up against other players, they're just my competitors.
"I measure my game; always have, towards the guys. I think I have the most to learn from them. So it's really trying to take baby steps to get better every day. I ain't going to finish this game before I feel like I've reached my potential."
Included amongst those in second position is the 2012 champion Jessica Korda who also played in the morning field and put together a bogey free round of 67. Korda is in good form at present having won in the Bahamas three weeks ago and finished 8th last week at RACV Royal Pines.
Amongst the large group at four under 68 is New Zealander Lydia Ko who got within one of the lead with three holes to play before bogeys at the 7th and 8th (her 16th and 17th) threatened to bring undone some very good work. She would birdie the 9th however for a solid start.
"It was a really good round," said the 16 year old. "I made a couple of silly mistakes like making a bogey on 8, which was a par 5. Most of the time you make a birdie, then a bogey, so I was a little upset about that but then I kind of finished it well with another birdie and that.
"I feel so relaxed here," she added referring to playing in Australia. "I play such good golf over here and everyone's supporting me, so I feel really relaxed. I think I'm more pressured when I'm home in New Zealand but it's always great to come out here and play in Australia."
The leading Australians are Sarah Jane Smith and last week's runner-up Minjee Lee who also opened with rounds of 68.
The conditions were so conducive to good scoring today that 59 players broke par on one of Australia's finest layouts and subject to no major change in the conditions tomorrow then it might take a score of even par to make the cut.