Data collected by NASA's Alice instrument aboard the European Space Agency's Rosetta spacecraft has provided surprising discovery about comet 67P/Churyumov-Gerasimenko's atmosphere.
Data collected by NASA's Alice instrument aboard the European Space Agency's Rosetta spacecraft has provided surprising discovery about comet 67P/Churyumov-Gerasimenko's atmosphere.
The probe revealed that electrons close to the surface of, not photons from the sun, as had been believed, cause the rapid breakup of water and carbon dioxide molecules spewing from the comet's surface.
Alan Stern, principal investigator, said that the discovery they're reporting is quite unexpected, adding it shows them the value of going to comets to observe them up close, since this discovery simply could not have been made from Earth or Earth orbit with any existing or planned observatory and it is fundamentally transforming their knowledge of comets.
Rosetta uncovers processes at work in comet’s coma. Image Credit: www.esa.int
Analysis of the relative intensities of observed atomic emissions allowed the Alice science team to determine the instrument was directly observing the "parent" molecules of water and carbon dioxide that were being broken up by electrons in the immediate vicinity, about six-tenths of a mile (one kilometre) from the comet's nucleus. The carbon dioxide and water are being released from the comet's nucleus and affected by electrons near the nucleus.
Since August 2014, Rosetta has orbited within 100 miles (160 kilometres) of comet 67P. The Alice spectrograph on board Rosetta specialises in sensing the far-ultraviolet wavelength band. Alice examines light the comet is emitting to understand the chemistry of the comet's atmosphere or coma. A spectrograph is a tool astronomers use to split light into its various colors. Scientists can identify the chemical composition of gases by examining their light spectrum. Alice is the first such far-ultraviolet spectrograph to operate at a comet.
Alice data indicate much of the water and carbon dioxide in the comet's coma originates from plumes erupting from its surface.
The study will appear in journal Astronomy and Astrophysics.
Watch: Rosetta’s imaging and spectroscopy instruments
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