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<\/a><\/p>\nThese images from Mars Color Imager (MARCI) aboard NASA\u2019s Mars Reconnaissance Orbiter (MRO) show Mars before (left) and during (right) the June 2018 dust storm. Image credit: NASA \/ JPL-Caltech \/ University of Arizona.<\/p>\n
\u201cSolar energetic particle (SEP) events occur when solar flares and coronal mass ejections (CMEs) release high-energy charged particles into space,\u201d said Lancaster University astronomer Lana Williams and colleagues.<\/p>\n
\u201cMars is particularly exposed to these particles because it has a thin atmosphere and no strong global magnetic field to shield the planet, as Earth does.\u201d<\/p>\n
\u201cPrevious research has shown that SEPs can affect Mars\u2019 upper atmosphere, causing ionization, diffuse aurorae and disruption to radio signals.\u201d<\/p>\n
\u201cBut their possible effects on the lower atmosphere, where weather processes take place, are not well understood.\u201d<\/p>\n
\u201cDust storms naturally heat parts of the Martian atmosphere by absorbing sunlight,\u201d they added.<\/p>\n
\u201cHowever, we found that the pattern of heating observed during the combined event was unusual for a dust storm and could not be explained by the storm alone.\u201d<\/p>\n
In the study, Williams and co-authors examined five SEP events at Mars to find out whether long-lasting SEPs could warm Mars\u2019 lower atmosphere, where its weather happens.<\/p>\n
Four of the SEP events showed no clear effect, but the fifth \u2014 which occurred in June 2018 \u2014 unexpectedly coincided with an expanding global dust storm that also wiped out NASA\u2019s Opportunity rover.<\/p>\n
It was during this event that signs of lower atmospheric heating were detected.<\/p>\n
\u201cWe expected that these highly energetic particles might have some effect on temperatures in Mars\u2019 lower atmosphere, but in four of the five events we studied we found no clear evidence of heating,\u201d Williams said.<\/p>\n
\u201cThe one exception occurred while a global dust storm was expanding across the planet.\u201d<\/p>\n
For the study, the astronomers used data from NASA\u2019s Mars Atmosphere and Volatile EvolutioN (MAVEN) spacecraft and ESA\u2019s Trace Gas Orbiter.<\/p>\n
They compared the observations with expected temperature profiles from the Mars Climate Database.<\/p>\n
They examined temperatures before, during and after the five long-lasting SEP events.<\/p>\n
\u201cDust storms were not originally part of our investigation, so finding one happening at the same time as the heating was unexpected,\u201d Williams said.<\/p>\n
\u201cIt suggests that Mars\u2019 atmosphere and weather may respond to several events acting together, rather than each source of heating operating independently.\u201d<\/p>\n