<SYSTEM_TASK:>
Solve the following problem using Python, implementing the functions described below, one line at a time
<END_TASK>
<USER_TASK:>
Description:
 def min_geodetic_distance(a, b):
 """ Compute the minimum distance between first mesh and each point of the second mesh when both are defined on the earth surface. :param a: a pair of (lons, lats) or an array of cartesian coordinates :param b: a pair of (lons, lats) or an array of cartesian coordinates """

    if isinstance(a, tuple):
        a = spherical_to_cartesian(a[0].flatten(), a[1].flatten())
    if isinstance(b, tuple):
        b = spherical_to_cartesian(b[0].flatten(), b[1].flatten())
    return cdist(a, b).min(axis=0)