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Auroras are dancing waves of light like the northern lights seen on Earth which have captivated people for millennia. They appear on a planet when solar activity disturbs its atmosphere.
The latest observations by EMM include a never-before-seen phenomenon, dubbed the ‘sinuous discrete aurora’ — a huge worm-like aurora that extends halfway around the Red Planet.
”When we first imaged Mars’ discrete aurora shortly after the Hope probe arrived at Mars in 2021, we knew we had unveiled new potential to make observations never before possible on this scale, and we took the decision to increase our focus on these auroras,” said EMM Science Lead, Hessa Al Matroushi.
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The sinuous discrete aurora consists of long worm-like streaks of energized electron emission in the upper atmosphere extending many thousands of kilometers (km), stretching from the dayside into the night side of Mars, EMM said.
The aurora observations were imaged when Mars was experiencing the effect of a solar storm, resulting in a faster, more turbulent stream of solar wind electrons than usual. The observations are some of the brightest and most extensive yet seen by Hope.
The mission scientists noted that the interplanetary magnetic field is carried by the solar wind and drapes around Mars, combining with magnetism in the Martian crust to form Mars’ magnetotail, a complex array of magnetic fields on the Martian night side.
”Having additional bandwidth and resources available to us meant we could be opportunistic and focus more on the area of discrete auroras than we had originally planned,” said Omran Sharaf, EMM project director.
”That agility has certainly paid off as we have now opened up whole new avenues of investigation into these transient and dynamic phenomena. Novel science was a core mission objective and this is certainly novel,” Sharaf said.
Observations made using Hope’s EMUS (The Emirates Mars Ultraviolet Spectrometer) instrument range between 90-180 nanometre (nm) wavelengths, according to EMM.
The ultraviolet (UV) emissions imaged in the new set of observations show where energetic electrons are smashing into atoms and molecules in the Martian upper atmosphere, some 130 km above the planetary surface.
These electrons come from the solar wind and are energized by electric fields in Mars’ magnetosphere or space around Mars with the dominant magnetic field of the Red Planet, the team explained.
”The sinuous discrete aurora was a shocking discovery that in many ways has us scratching our heads and going back to the drawing board. We have ideas, but no solid explanation for why we are observing intense aurora of this shape and at planetary scales,” Rob Lillis, EMUS team member at the University of California, Berkeley, US.
”We now have the opportunity to re-examine prior observations of Mars by missions such as MAVEN and Mars Express to search for signatures that could flesh out Hope’s new observations and perhaps help us try and unpick quite what is happening here,” Lillis said in the statement.
Three types of aurora have previously been observed around Mars: the diffuse aurora is observed only during intense solar storms when interactions with the highest energy particles cause the atmosphere around the entire planet to light up, mission researchers said.
The discrete aurora, on the other hand, is highly localized and observations made to date have appeared to bear out the theory that it is directly linked to the patchy magnetic fields produced by magnetized minerals embedded in Mars’ crust, said.
Both of these aurorae are observed on Mars’ nightside, while a third class, the proton aurora, has been measured on Mars’ dayside and is driven by interactions between the solar wind and hydrogen in Mars exosphere.
These three types of aurora had previously been identified, but clear global images of the discrete aurora were elusive until new observations were made by EMM’s probe shortly after its arrival on Mars in February 2021.