DUBAI 28 April 2022: The Emirates Mars Mission, the first interplanetary exploration undertaken by an Arab nation, released stunning new images of Mars’ enigmatic discrete auroras on Wednesday, following a new series of revolutionary observations that promise new answers – and new questions – about the interactions between Mars’ atmosphere, the planet’s magnetic fields and the solar winds.
The observations include a never-before-seen phenomenon, dubbed the ‘sinuous discrete aurora’ by the EMM team, a huge worm-like aurora that extends halfway around the planet.
“When we first imaged Mars’ discrete aurora shortly after the Hope probe arrived at Mars in 2021, we knew we had unveiled a new potential to make observations never before possible on this scale, and we took the decision to increase our focus on these auroras,” said Emirates Mars Mission Science Lead, Hessa Al Matroushi. “We can obtain nearly whole-disk, synoptic snapshots of the atmosphere to investigate atmospheric phenomena and interactions. It means we are seeing discrete auroral effects on a massive scale and in ways we never anticipated.”
The sinuous discrete aurora consists of long worm-like streaks of energised electron emissions in the upper atmosphere, extending many thousands of kilometres, stretching from the dayside into the nightside of Mars. Imaged when Mars was experiencing the effect of a solar storm, resulting in a faster, more turbulent stream of solar wind electrons than usual, these aurora observations are some of the brightest and most extensive yet seen by Hope. They include elongated shapes, which may be caused by similarly elongated regions of electron energisation conditions in the magnetotail.
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 nightside.
“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. 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,” said Omran Sharaf, EMM project director.
Observations made using Hope’s EMUS (The Emirates Mars Ultraviolet Spectrometer) instrument range between 90-180 nanometre wavelengths. Found at a wavelength of 130.4 nm, the 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 energised by electric fields in Mars’ magnetosphere.
“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 an intense aurora of this shape and at planetary scales. 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 what is happening here,” said Dr. Rob Lillis, EMUS team member at the University of California, Berkeley.
Electrons follow magnetic field lines, so their paths to the atmosphere are determined by the magnetic fields in this environment. The new observations made by Hope include ‘draped’ field lines, which don’t touch the nightside atmosphere, ‘closed’ field lines which connect to the crust at both ends, and ‘open’ field lines which connect the crust to the solar wind. These ‘open’ field lines funnel electrons toward the atmosphere in sometimes intricate patterns, which are then reflected in the resulting UV emission detected by EMUS. Because they are spatially confined, these emissions are known as “discrete auroras”.
Alongside auroras defined by Mars’ crustal field, the complex shapes of energised electron impact observed by Hope open up new avenues for our understanding of how the combination of planetary and solar interactions impact Mars’ atmospheric dynamics.
The Hope Probe’s historic arrival at the Red Planet coincided with a year of celebrations to mark the UAE’s Golden Jubilee in 2021.