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 wind, the Emirates Mars Mission, the first interplanetary exploration undertaken by an Arab nation, released stunning new images of Mars’ enigmatic discrete auroras. The observations include a previously unseen phenomenon, dubbed the’sinuous discrete aurora’ by the EMM team, which is a massive worm-like aurora that extends halfway around the planet.
“When we first imaged Mars’ discrete aurora shortly after the Hope probe’s arrival 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 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 is made up of long worm-like streaks of energised electron emission in the upper atmosphere that stretch for thousands of kilometers from Mars’ dayside to its nightside. These aurora observations, captured while Mars was experiencing the effects of a solar storm, resulting in a faster, more turbulent stream of solar wind electrons than usual, are some of the brightest and most extensive yet seen by Hope. They have elongated shapes, which could be caused by similarly elongated electron energization conditions in the magnetotail.
The solar wind carries the interplanetary magnetic field around Mars, where it combines with magnetism in the Martian crust to form Mars’ magnetotail, a complex array of magnetic fields on the Martian nightside.
Omran Sharaf, EMM project director, said, “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.”
Hope’s EMUS (The Emirates Mars Ultraviolet Spectrometer) instrument observed wavelengths ranging from 90 to 180 nanometres. The UV emissions imaged in the new set of observations, which have a wavelength of 130.4 nm, show where energetic electrons are smashing into atoms and molecules in the Martian upper atmosphere, some 130 km above the planetary surface. These electrons are energized by electric fields in Mars’ magnetosphere and come from the solar wind.
Dr. Rob Lillis, EMUS team member at the University of California, Berkeley, said: “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. 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.”
Because electrons follow magnetic field lines, the magnetic fields in this environment determine their paths to the atmosphere. Hope discovered ‘draped’ field lines that do not touch the nightside atmosphere, ‘closed’ field lines that connect to the crust at both ends, and ‘open’ field lines that connect the crust to the solar wind. These ‘open’ field lines funnel electrons toward the atmosphere in sometimes complex patterns, which are then reflected in the UV emission detected by EMUS. These emissions are known as “discrete auroras” because they are spatially confined.
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 the way in which the combination of planetary and solar interactions impact Mars’ atmospheric dynamics.
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. In contrast, the discrete aurora is highly localised 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. 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. Now, an increased focus on discrete aurora observations by the EMM science team has resulted in observations of this new phenomenon of sinuous discrete aurora. “Since those first observations of the discrete aurora, we have continued to see incredible new patterns of aurora that open new insights into the interactions of charged particles in the Martian atmosphere,” said Al Matroushi. “There is a very great deal of new information here for the EMM science team to unpick.”
One of three instruments on board Mars Hope Probe, EMUS’ principal science goal is the measurement of oxygen and carbon monoxide in Mars’ thermosphere and the variability of hydrogen and oxygen in the exosphere.
Hope is in its planned 20,000–43,000 km elliptical science orbit, with a 25-degree inclination to Mars. During its two-year mission to map Mar’s atmospheric dynamics, the probe completes one orbit of the planet every 55 hours and collects a full planetary data sample every nine days.
EMM and the Hope probe are the result of a knowledge transfer and development effort that began in 2006, with Emirati engineers collaborating with partners around the world to develop the UAE’s spacecraft design, engineering, and manufacturing capabilities. Hope is a self-contained spacecraft carrying three instruments to measure the atmosphere of Mars. The spacecraft, which weighs about 1,350 kg and is about the size of a small SUV, was designed and developed by MBRSC engineers in collaboration with academic partners such as LASP at the University of Colorado, Boulder, Arizona State University, and the University of California, Berkeley.
The Emirates Mars Mission is studying the Martian atmosphere and the relationship between the upper layer and lower regions, providing the international scientific community with a comprehensive view of the Martian atmosphere at various times of the day and throughout the seasons for the first time. Every three months, science data is released, and the information is made freely available to researchers and enthusiasts worldwide.
The historic arrival of the Hope Probe on Mars coincided with a year of celebrations to mark the UAE’s Golden Jubilee in 2021.