There is nothing definitive about it. The paper describes many factors
that could change the D/H ratio in different samples, and is much more
cautious in its conclusions than the typical press reports suggest:
"From the ROSINA measurements on comet 67P/Churyumov-Gerasimenko, we
conclude that the D/H values of JFCs [Jupiter family comets] may be
highly heterogeneous, possibly reflecting the diverse origins of JFCs.
If this is the case, then the new measurement supports models advocating
an asteroidal (i.e., carbonaceous chondrite-like), rather than cometary
origin for the oceans, and by extension for the terrestrial atmosphere."
Chris
*******************************
Chris L Peterson
Cloudbait Observatory
http://www.cloudbait.com
On 12/12/2014 1:50 PM, Michael Mulgrew via Meteorite-list wrote:
I am curious how such a definitive conclusion can be reached from the
analysis of a singular cometary body? How many comets are out there
floating around the solar system? I guess they are assuming all
comets have the same make-up? Seems a bit short sighted to me,
considering, for example, how diverse asteroidal composition is.
Imagine if we landed a probe on one asteroid, then extrapolated the
results of that landing to apply to all asteroids, what a gross
neglect of diversity that would be.
Hopefully I'm missing something here and someone will chime in and
explain it to me.
Michael in so. Cal.
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