New science is not always required if something odd is noticed.
True but this is a little different from your example. There is no fundamental law of physics saying that you cannot build an instrument large enough to observe distant planets. In the absence of such a restriction building that instrument is down to human ingenuity. However there is a fundamental law of physics which says that momentum is conserved.
As a result this force is either due to some interaction with the surroundings that the experiment has forgotten to account for or is due to new physics in the form of new particles/interactions or violation of conservation of momentum - which is an extremely fundamental law of physics. There really are no "loopholes" to squeeze through.
My personal feeling is that it will turn out to be some effect which they forgot to account for although I cannot help but hope that it turns out to be something far more interesting...which is why it is so easy to fool ourselves when doing experiments.