The now defunct microbar on Lavender Hill did a selection and they were worth crossing town for.    From Wordnik.com.  [British Blogs] Reference

A microbar is one one-millionth of an Earth atmospheric pressure, so Pluto's surface pressure is between 1 / 300th and 1 / 1000th as on Mars's surface.    From Wordnik.com.  [Space News From SpaceDaily.Com] Reference