The so-called Minimum Orbit Intersection Distance (MOID) of 3I/ATLAS from Mars, namely the closest that 3I/ATLAS gets to the complete path of Mars around the Sun is remarkably short, just 0.018 AU or 2.7 million kilometers. This by itself constitutes another rare anomaly of 3I/ATLAS. If 3I/ATLAS is a technological mothership, this proximity makes it easy for it to release a mini-probe that would reach Mars easily with the appropriate ejection velocity. In addition, a small orbit correction by 3I/ATLAS could shrink this MOID of Mars to zero.
https://avi-loeb.medium.com/the-challenge-of-measuring-the-mass-of-3i-atlas-7490db969838