Jonas Hanson was a Captain in the United States Air Force and leader of SG-9. When the team first met the cave-dwellers of Avnil (P3X-513), they immediately bowed down to them in thought that they were gods. Hanson didn't deny it and told the rest of the team that it might be safer if they allowed the inhabitants to think he was a god for a while and said it was the system of government they needed to retake their world. In their fourth or fifth week on the planet, a young child wandered out of the caves. Hanson went out after him and was gone for two full days before he came back, carrying the child, barely alive, in his arms. The cave dwellers loved him for that.
When a few cave dwellers, thanks to Lt. Thomas Frakes and Lt. Laurence Conner, got the idea that Hanson was just a man like they were, he had them tied to stakes and left out in direct sunlight. They were there seven days before they were allowed back in the caves. After that they were blind with giant bleeding burns all over them. It took a while, but soon they died.
When Frakes and Conner tried to escape through the Stargate, he had the cave dwellers hunt them down. They captured Frakes and brought him before Hanson. He shot him and ordered Lt. Matthew Baker to burn the body. Conner however was able to dial Earth and SG-1 came to investigate.
After having found a solar radiation shield, he made the cave dwellers build a temple and promised them he would activate it. When Baker captured Captain Samantha Carter, he forced her to activate it or he would kill Conner and Colonel Jack O'Neill. Carter agreed in order to save both Conner and O'Neill's lives, and so switched the device on.
Rather than honoring the deal he had made, Hanson took Conner and O'Neill back to the Stargate which he had tilted so it was horizontal in order for him to bury it after its final use. Forcing the two to the edge of the Stargate, Hanson proclaimed that he now had the power to stop the sun from affecting the population to the Avnilians, informing them that he was going to bury the Stargate so that no more demons could come through. First, however, he planned to send O'Neill and Conner back to Earth without sending an IDC which would mean that the iris on Earth's Stargate would kill them instantly. Though Carter argued that this would be tantamount to killing them, Hanson ignored her and went forward with his plan. It was only due to the timely intervention of Dr. Daniel Jackson and Jamala, the local who was helping SG-1, that the two Tau'ri were saved. Rather than sending Conner and O'Neill through the Stargate, SG-1 managed to convince the Avnilians that Hanson was not a god by activating the shield which would protect them from the UV radiation.
Angry, the Avnilians picked Hanson up and threw him through the Stargate to Earth. Due to the fact that an IDC hadn't been sent through which would enable the iris to be opened, Hanson was killed on impact when he hit the closed iris. (SG1: "The First Commandment")
At first glance, Hanson appeared to be a sincere, charming, even sane man but this was later revealed to be nothing more than a facade as he was in a fact a power-hungry, controlling and ruthless man displaying psychopathic or sociopathic traits.
In addition to his arrogance, Hanson was also willing to keep his position of power to such an extent that he was willing to kill the members or any Avnilian who dared to stand against him.
- Jonas Hanson used to be engaged to be married with Samantha Carter. However, this relationship ended when Carter got tired of his controlling behavior.