Early orbital predictions for the near-Earth asteroid 2001 CA21 — based on 2015 JPL Horizons data — revealed a trajectory with an eccentricity of 0.777, a perihelion of 0.373 AU, and an aphelion extending to 2.967 AU. While subsequent refinements altered the asteroid’s actual orbit, these initial parameters provided a valuable reference template for designing rapid Earth–Mars transfers. By anchoring transfer-plane geometry to the CA21 orbital solution, we identified novel mission opportunities capable of drastically reducing interplanetary travel times.Our analysis highlights the 2031 opposition as the most favorable case: a 56-day transfer with , only marginally exceeding the New Horizons record, and , challenging but potentially addressable with aerocapture or braking tug concepts. A 33-day extreme trajectory is also geometrically possible in 2031, though requiring departure energies ( ) and arrival speeds ( ) well beyond current or near-term propulsion systems.Earlier opportunities in 2027 and 2029, while closer in time, impose even higher energetic barriers (departure velocities ~19 km/s, arrival ~17.5–20 km/s), underscoring the counterintuitive reality that shorter Earth–Mars distances do not guarantee lower transfer energy.This study therefore proposes a new methodological framework: using early asteroid orbital predictions as trajectory templates to identify both feasible and aspirational rapid-transit missions. By linking NEO orbital geometry with Lambert-based transfer analysis, we establish practical benchmarks for propulsion and capture technologies, demonstrating that 2031 provides a near-term achievable baseline, while also defining the aspirational frontier of one-month Mars missions.