Consider the following passage:
Planetary scientists long posited that complex organic molecules discovered on comets originated strictly within interstellar cold clouds prior to the formation of the presolar nebula. Critics of this interstellar origin hypothesis countered that solar ultraviolet irradiation during the early protoplanetary disk phase was sufficient to synthesize these organic compounds in situ from simpler volatile ice species. To support their counterargument, these critics pointed to laboratory simulations in which volatile ice mixtures subjected to disk-level UV exposure yielded complex amino acid precursors identical to those retrieved from cometary samples.
However, astrochemists recently offered a rebuttal to this in situ synthesis argument by analyzing deuterium-to-hydrogen (D/H) isotopic ratios within cometary organic matter. Their measurements revealed an extreme deuterium enrichment that chemically requires formation temperatures consistently below 20 Kelvin. Because thermodynamic modeling demonstrates that even the outermost regions of the protoplanetary disk maintained temperatures well above 40 Kelvin during the period of peak solar UV flux, the astrochemists argued that in situ disk synthesis cannot account for the observed isotopic profile.
Evaluate the following statement based on the passage:
The astrochemists' rebuttal successfully neutralizes the in situ disk synthesis counterargument by demonstrating that a thermodynamic condition required for the cometary organics' isotopic signature was absent during the protoplanetary disk phase.
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