What's the distance (in light-seconds and light-minutes) from Earth to Mars?

earth_mars.py

"""
Compute and display the Earth-Mars distance in light-seconds, light-minutes
and kilometers.

The easiest way is to install both ``skyfield`` & ``skyfield-data`` to compute
this:

    $ pip install skyfield skyfield-data

You can also install `skyfield` only, but it'll force you to download the
`de421.bsp` file (at relatively slow speed, as far as I tested it, maybe it's
because the install of ``skyfield-data`` is compressed in the .whl file).
Fortunately, this file download is made only once, since the file is in your
current directory.

"""
try:
    from skyfield_data import get_skyfield_data_path
except ImportError:
    from skyfield.api import load
else:
    from skyfield.api import Loader
    load = Loader(get_skyfield_data_path())
finally:
    time = load.timescale().now()

planets = load('de421.bsp')

v = planets['mars'].at(time) - planets['earth'].at(time)
km = v.distance().km
ls = v.distance().light_seconds()
lmin = ls / 60.
print(f'Mars is {ls} light-seconds away ({lmin} min -- {km} km)')