Spectral data of Comet 238 P/Read and Comet 109 P/Hartley 2

This graphic presentation of spectral data highlights a key similarity and difference between observations of Comet 238P/Read by the NIRSpec (Near-Infrared Spectrograph) instrument on the NASA/ESA/CSA James Webb Space Telescope in 2022 and observations of Comet 103P/Hartley 2 by NASA’s Deep Impact mission in 2010. Both show a distinct peak in the region of the spectrum associated with water. Finding this in Comet Read was a significant accomplishment for Webb, as it is in a different class of comets than Jupiter-family comets like Hartley 2, and this marks the first time that a gas has been confirmed in such a main belt comet. However, Comet Read did not show the characteristic, expected bump indicating the presence of carbon dioxide.

[Image description: Graph comparing the spectral data of Comet 238 P/Read and Comet 109 P/Hartley 2, highlighting the detection of water in both, and the absence of carbon dioxide in Comet Read.]