Editing Oxygen (section)

===Analysis===
[[File:Phanerozoic Climate Change.png|thumb|left|upright=1.15|500 million years of [[Climate variability and change|climate change]] vs. <sup>18</sup>O|alt=Time evolution of oxygen-18 concentration on the scale of 500 million years showing many local peaks.]]

[[Paleoclimatology|Paleoclimatologists]] measure the ratio of oxygen-18 and oxygen-16 in the [[Exoskeleton|shells]] and [[skeleton]]s of marine organisms to determine the climate millions of years ago (see [[oxygen isotope ratio cycle]]). [[Seawater]] molecules that contain the lighter [[isotope]], oxygen-16, evaporate at a slightly faster rate than water molecules containing the 12% heavier oxygen-18, and this disparity increases at lower temperatures.<ref name="NBB304">[[#Reference-idEmsley2001|Emsley 2001]], p. 304</ref> During periods of lower global temperatures, snow and rain from that evaporated water tends to be higher in oxygen-16, and the seawater left behind tends to be higher in oxygen-18. Marine organisms then incorporate more oxygen-18 into their skeletons and shells than they would in a warmer climate.<ref name="NBB304" /> Paleoclimatologists also directly measure this ratio in the water molecules of [[ice core]] samples as old as hundreds of thousands of years.{{cn|date=May 2025}}

[[Geology of solar terrestrial planets|Planetary geologists]] have measured the relative quantities of oxygen isotopes in samples from the [[Earth]], the [[Moon]], [[Mars]], and [[meteorite]]s, but were long unable to obtain reference values for the isotope ratios in the [[Sun]], believed to be the same as those of the [[Nebular hypothesis|primordial solar nebula]]. Analysis of a [[silicon]] wafer exposed to the [[solar wind]] in space and returned by the crashed [[Genesis (spacecraft)|Genesis spacecraft]] has shown that the Sun has a higher proportion of oxygen-16 than does the Earth. The measurement implies that an unknown process depleted oxygen-16 from the Sun's [[Protoplanetary disk|disk of protoplanetary material]] prior to the coalescence of dust grains that formed the Earth.<ref>{{cite journal|last = Hand|first = Eric|title = The Solar System's first breath|journal = Nature|volume = 452|page = 259|date = March 13, 2008|doi = 10.1038/452259a|pmid = 18354437|issue = 7185|bibcode = 2008Natur.452..259H |s2cid = 789382|doi-access = free}}</ref>

Oxygen presents two spectrophotometric [[absorption band]]s peaking at the wavelengths 687 and 760&nbsp;[[Nanometre|nm]]. Some [[remote sensing]] scientists have proposed using the measurement of the radiance coming from vegetation canopies in those bands to characterize plant health status from a [[Earth observation satellite|satellite]] platform.<ref>{{cite conference|title=Progress on the development of an integrated canopy fluorescence model|last1=Miller|first1=J. R.|display-authors=4|author2=Berger, M.|author3=Alonso, L.|author4=Cerovic, Z.|author5=Goulas, Y.|author6=Jacquemoud, S.|author7=Louis, J.|author8=Mohammed, G.|author9=Moya, I.|author10=Pedros, R.|author11=Moreno, J.F.|author12=Verhoef, W.|author13=Zarco-Tejada, P.J.|work=Geoscience and Remote Sensing Symposium, 2003. IGARSS '03. Proceedings. 2003 IEEE International|year=2003 |volume=1 |pages=601–603 |doi=10.1109/IGARSS.2003.1293855|isbn=0-7803-7929-2 |citeseerx=10.1.1.473.9500}}</ref> This approach exploits the fact that in those bands it is possible to discriminate the vegetation's [[reflectance]] from its [[fluorescence]], which is much weaker. The measurement is technically difficult owing to the low [[signal-to-noise ratio]] and the physical structure of vegetation; but it has been proposed as a possible method of monitoring the [[carbon cycle]] from satellites on a global scale.{{cn|date=May 2025}}
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