I recently made a plot of the masses and orbital radii of the known planets -- both extrasolar and those in the Solar System. I looked up Pluto's mass in two books, and the reported values differed by almost an order of magnitude -- 0.0023 versus 0.02561 Earth masses!

Shocked, shocked, I looked up the mass in every appropriate book on my shelf. Here's the data:

	Pluto's Mass (M_E)  Source
	******************************************************************************************
	0.9		    Astrophysical Quantities (Allen - 1955)
	0.002		    The Evolving Universe: An Introduction to Astronomy (Goldsmith - 1982)
	0.0023		    The Physical Universe: An Introduction to Astronomy (Shu - 1982)
	0.02561		    Astrophysical Data: Planets & Stars (Lang - 1992)
	0.0018		    Intro to Astronomy & Astrophysics (Zelik & Gregory - 1998)
	0.0025		    Astronomy: From the Earth to the Universe (Pasachoff - 1998)
	0.002200	    Allen's Astrophysical Quantities (Cox - 2000)
	0.0022		    Life in the Universe (Bennett, Shostak & Jakosky - 2003)

I also have a copy of The Planetary Science Companion, by Lodders & Fegley (1998). It cites actual papers with measurements, so it seems like a good source. It points out that "Pluto's mass" is not well defined. Do you include the mass of its moon, Charon, which is about 10-15% of the total mass? Here's some data from this book:

	System mass (M_E)	Pluto's mass (M_E)	Reference
	*********************************************************
	0.002471 +/- 0.000030	0.002200 +/- 0.000030	[NO96]
	0.002462 +/- 0.000003	0.002218 +/- 0.000119	[TB97]
	0.002397 +/- 0.000022	0.002072 +/- 0.000020	[YOE94]

	[NO96] = Null & Owen (1996), Astron. J. 111, 1368-1381.
	[TB97] = Tholen & Buie (1997), Icarus 125, 245-260.
	[YOE94] = Young, Olkin, Elliot, Tholen & Buie (1994), Icarus 108, 186-199.

So, it seems that 0.02561 Earth masses was a misprint in Astrophysical Data: Planets & Stars. With such an error, the extra decimal places look silly -- you know those astronomers: often in error, but never in doubt.