October 1, 2007 | David F. Coppedge

Comet Woes: News Reports Hide Backroom Exasperation

“Comets are made of the most primitive stuff in the solar system,” a press release from University of Michigan triumphantly claimed today.  “As hunks of rock and ice that never coalesced into more planets, they give researchers clues to the evolution of solar systems.”
    Tell that to Toby Owen and two colleagues who just published a paper in Icarus.1  They measured the nitrogen to carbon ratio from several real comets and found it 300 times smaller than expected, if the comets had formed in the primitive outer reaches of the solar system.  Having established the deficit experimentally, they tried to explain it, saying, “we have to guess what was the N2/CO ratio where the ice grains which agglomerated to form comet nuclei were formed, either at the outskirts of the solar nebula or in the dense interstellar cloud which collapsed to form the nebula, assuming that their composition was not changed” (italics theirs).  That, of course, was the assumption in the U Michigan press release.  “Where has the nitrogen disappeared?”
    They looked again at the expected ratio, and compared it with their actual measurements.  They looked at various ways of bringing the numbers in line.  Way off still.  “At this point we raise our hands,” they said – a statement of exasperation rare for a dignified scientific paper.  “In conclusion, we do not know what has happened to the missing nitrogen” (italics theirs).  Earlier, they said they had accepted the usual assumptions about comet formation (see footnote also for historical reference to Halley’s speculation about Noah’s flood).2
    Meanwhile, the U Michigan press release paraded on, assuring the readers that each piece of data was coming together into a complete understanding of not only comets but entire solar systems.  “As for what these observations say about the origins of the solar system, scientists don’t know just yet,” the article admitted, but then quoted a confident researcher, “The composition of comets tells us about conditions approximately 4.5 billion years ago when the solar system was formed.”


1.  A. Bar-Nun, G. Notesco and T. Owen, “Trapping of N2, CO and Ar in amorphous ice—Application to comets,” Icarus, Volume 190, Issue 2, October 2007, Pages 655-659, doi:10.1016/j.icarus.2007.03.021.
2.  “In previous papers, we have supported the idea that icy planetesimals (aka comets) could have brought heavy noble gases and other volatiles to the inner planets ([Owen and Bar-Nun, 1995], [Owen and Bar-Nun, 1998] and [Owen et al., 2000]).  This concept can be traced back to Edmond Halley (1724) who thought a collision with a comet could have produced Noah’s flood.  More recently, the role of comets in bringing volatiles to the Earth has been championed by Or� (1961), Sill and Wilkening (1978) and especially Delsemme (2000, and references therein).  Our approach to this venerable idea has been to assume that the water ice in comets formed in the amorphous state at temperatures below ~50 K and trapped ambient gases in the process.”

Don’t you wish the science reporters would just tell it like it is?  Don’t they think we can handle the truth?  Do they assume the public would freak out if they showed a little humility for a change? (09/29/2007).

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Categories: Solar System

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