One of the main sources of tension in the story is the implication that the team might not make it back to the surface because the ship was launched in the future as a tentative unmanned probe but they now know exactly when and why it crashed and if the team reaches the surface they'll cause a temporal paradox by preventing the ship from crashing. Why does it never occur to anyone that they could just not tell anyone about the crash or tell them but make sure that the ship's mission is planned anyway. Sure that wouldn't solve the other problems, but at least it would take care of the one that they knew about.
Those three are not trained to lie successfully. The Navy spent millions of dollars and lost multiple personnel so the characters are going to be undergoing weeks of debriefing to determine what happened down there. They're bound to slip up. Wiping their own memory is the only way to be sure. Additionally, they didn't want to have the power.
Though actually one of them did want to keep the power, but concede the others' point that they're not ready.
