The UAE’s Hope probe has captured rare images of the discrete aurora in Mars’ night side atmosphere.
The findings, captured by Hope’s ultraviolet spectrometer instrument, would help scientists understand the interactions between solar radiation, Mars’ magnetic fields and the atmosphere.
On Earth, the aurora borealis and aurora polaris (known as as northern lights) happen when protons and electrons from solar wind hit the particles in the atmosphere, causing colourful lights in the sky.
On Mars, however, there are three types of aurorae – proton, diffuse and discrete – because of its lack of a global magnetic field and localised crustal magnetic fields in the southern hemisphere.
Only the proton aurora, which occurs during the day, has been captured before in detail, while the other have only been caught in signatures – all by Nasa missions.
“We have totally blown out ten years of study of Mars’ auroras with ten minutes of observations,” said Justin Deighan, the Emirates Mars Mission deputy science lead.
“The data we are capturing confirms the tremendous potential we now have of exploring Mars’ aurora and the interactions between Mars’ magnetic fields, atmosphere and solar particles with a coverage and sensitivity we could only previously dream of.
“These exciting observations go above and beyond the original science goals of the Emirates Mars Mission.”
Aurorae in Mars’ night side atmosphere are extremely rare to capture, however, Hope has a higher possibility of imaging the phenomenon than any other spacecraft because of its unique elliptical orbit around the planet. It observes the night side on every one of its 55-hour orbits of the planet.
Nasa’s MAVEN mission has only captured discrete aurora’s signatures in less than 1 per cent of the night side observations since it started collecting data in 2014.
Hessa Al Matroushi, science lead of the mission, said the findings are unique global snapshots of the discrete aurora and it is the first time such clear observations have been made globally and in these wavelengths.
“The implications for our understanding of Mars’ atmospheric and magnetospheric science are tremendous and provide new support to the theory that solar storms are not necessary to drive Mars’ aurora,” she said.
What causes Martian aurorae?
Discrete aurora occurs around Mars’ irregular crustal magnetic field, which is caused by deep deposits of magnetised iron bearing minerals in the planet’s crust.
It is created when energetic electrons in the upper atmosphere collide with gas molecules in the atmosphere, which causes ionisation, dissociation of molecules and emission of photons.
The diffuse aurora has only been observed during intense solar storms, when interaction with the highest energy particles cause the atmosphere around the entire planet to light up.
The proton aurora happens during the day and is caused by the interaction between the solar wind and hydrogen in Mars’ exosphere.
“Mars’ aurorae are an area of intense interest to the global scientific community and their study has tremendous potential to challenge, expand and deepen our understanding of Mars’ atmosphere and its interaction with the planet and with solar energies,” said Al Matroushi.
“We were hopeful that EMUS could make a contribution in this area but we now know with absolute certainty that contribution is going to be ground breaking.”
How does this finding aid Hope’s mission?
The findings were not part of the mission’s agenda, however, they are still valuable to the scientific community.
The observations question previous theories of the role solar particles play in causing aurora in the planet’s atmosphere.
Hope’s mission is to study the upper and lower atmosphere of the planet. Using its ultraviolet spectrometer, it has been measuring oxygen and carbon monoxide in the thermosphere, as well as the presence of hydrogen and oxygen in the exosphere.
The Emirates Mars Mission team will reveal more findings in October.