  Recently, there has been a surge of international interest in
extraterrestrial exploration targeting the Moon, Mars, the moons of Mars, and
various asteroids. This contribution discusses how current state-of-the-art
Earth-based testing for designing rovers and landers for these missions
currently leads to overly optimistic conclusions about the behavior of these
devices upon deployment on the targeted celestial bodies. The key misconception
is that gravitational offset is necessary during the \textit{terramechanics}
testing of rover and lander prototypes on Earth. The body of evidence
supporting our argument is tied to a small number of studies conducted during
parabolic flights and insights derived from newly revised scaling laws. We
argue that what has prevented the community from fully diagnosing the problem
at hand is the absence of effective physics-based models capable of simulating
terramechanics under low gravity conditions. We developed such a physics-based
simulator and utilized it to gauge the mobility of early prototypes of the
Volatiles Investigating Polar Exploration Rover (VIPER), which is slated to
depart for the Moon in November 2024. This contribution discusses the results
generated by this simulator, how they correlate with physical test results from
the NASA-Glenn SLOPE lab, and the fallacy of the gravitational offset in rover
and lander testing. The simulator developed is open sourced and made publicly
available for unfettered use; it can support principled studies that extend
beyond trafficability analysis to provide insights into in-situ resource
utilization activities, e.g., digging, bulldozing, and berming in low gravity.
